Endangered and Threatened Wildlife and Plants; Endangered Status for Four Central Texas Salamanders and Designation of Critical Habitat

DEPARTMENT OF THE INTERIOR

Fish and Wildlife Service

50 CFR Part 17

[Docket No. FWS-R2-ES-2012-0035; 4500030114]

RIN 1018-AY22

Endangered and Threatened Wildlife and Plants; Endangered Status for Four Central Texas Salamanders and Designation of Critical Habitat

AGENCY:

Fish and Wildlife Service, Interior.

ACTION:

Proposed rule.

SUMMARY:

We, the U.S. Fish and Wildlife Service (Service), propose to list the Austin blind salamander, Jollyville Plateau salamander, Georgetown salamander, and Salado salamander as endangered under the Endangered Species Act of 1973, as amended (Act), and propose to designate critical habitat for the species. In total, we propose to designate approximately 5,983 acres (2,440 hectares) as critical habitat for the four species. The proposed critical habitat is located in Travis, Williamson, and Bell Counties, Texas.

DATES:

We will accept comments received or postmarked on or before October 22, 2012. Comments submitted electronically using the Federal eRulemaking Portal (see

ADDRESSES

section, below) must be received by 11:59 p.m. Eastern Time on the closing date. We must receive requests for public hearings, in writing, at the address shown in the

FOR FURTHER INFORMATION CONTACT

section by October 9, 2012.

Public Informational Sessions and Public Hearings:

We will hold two public informational sessions and two public hearings on this proposed rule. We will hold a public informational session from 5:30 p.m. to 6:30 p.m., followed by a public hearing from 7 p.m. to 8:30 p.m., in Round Rock, Texas, on Wednesday, September 5 (see

ADDRESSES

). We will hold a public informational session from 6:30 p.m. to 7:30 p.m., followed by a public hearing from 8 p.m. to 9:30 p.m., in Austin, Texas, on Thursday, September 6 (see

ADDRESSES

). Registration to present oral comments on the proposed rule at the public hearings will begin at the start of each informational session.

ADDRESSES:

Document availability:

You may obtain copies of the proposed rule on the Internet at

http://www.regulations.gov

at Docket No. FWS-R2-ES-2012-0035 or by mail from the Austin Ecological Services Field Office (see

FOR FURTHER INFORMATION CONTACT

).

The coordinates or plot points or both from which the maps are generated are included in the administrative record for this critical habitat designation and are available at (

http://www.fws.gov/southwest/es/AustinTexas/

),

http://regulations.gov

at Docket No. FWS-R2-ES-2012-0035, and at the Austin Ecological Services Field Office (see

FOR FURTHER INFROMATION CONTACT

). Any additional tools or supporting information that we may develop for this critical habitat designation will also be available at the above locations.

Written Comments:

You may submit written comments by one of the following methods:

(1)

Electronically:

Go to the Federal eRulemaking Portal:

http://www.regulations.gov.

Search for Docket No. FWS-R2-ES-2012-0035. You may submit a comment by clicking on “Comment Now!”

(2)

By hard copy:

Submit by U.S. mail or hand-delivery to: Public Comments Processing, Attn: FWS-R2-ES-2012-0035ES-2012-0035; Division of Policy and Directives Management; U.S. Fish and Wildlife Service; 4401 N. Fairfax Drive, MS 2042-PDM; Arlington, VA 22203.

We request that you send comments only by the methods described above. We will post all comments on

http://www.regulations.gov.

This generally means that we will post any personal information you provide us (see the Information Requested section below for more information).

Public informational sessions and public hearings:

The September 5, 2012, public informational session and hearing will be held at the Wingate by Wyndham Round Rock, 1209 N. IH 35 North, Exit 253 at Hwy 79, Round Rock, Texas 78664. The September 6, 2012, public informational session and hearing will be held at Thompson Conference Center, 2405 Robert Dedman Drive, Room 2.102, Austin, Texas 78705. People needing reasonable accommodations in order to attend and participate in the public hearings should contact Adam Zerrenner, Field Supervisor, Austin Ecological Services Field Office, as soon as possible (see

FOR FURTHER INFORMATION CONTACT

).

FOR FURTHER INFORMATION CONTACT:

Adam Zerrenner, Field Supervisor, U.S. Fish and Wildlife Service, Austin Ecological Services Field Office, 10711 Burnet Rd, Suite 200, Austin, TX 78758; by telephone 512-490-0057; or by facsimile 512-490-0974. Persons who use a telecommunications device for the deaf (TDD) may call the Federal Information Relay Service (FIRS) at 800-877-8339.

SUPPLEMENTARY INFORMATION:

Executive Summary

Why We Need to Publish a Rule

This is a proposed rule to list the Austin blind salamander (

Eurycea waterlooensis

), Jollyville Plateau salamander (

Eurycea tonkawae

), Georgetown salamander (

Eurycea naufragia

), and Salado salamander (

Eurycea chisholmensis

) as endangered.

With this rule, we are proposing to designate the following critical habitat for the four central Texas salamanders:

• Austin Blind salamander: 120 acres (49 hectares)

• Jollyville Plateau salamander: 4,460 acres (1,816 hectares)

• Georgetown salamander: 1,031 acres (423 hectares)

• Salado salamander: 372 acres (152 hectares)

The proposed critical habitat is located within Travis, Williamson, and Bell Counties, Texas.

The Basis for Our Action

Under the Endangered Species Act, we can determine that a species is endangered or threatened based on any of the following five factors: (A) Destruction, modification, or curtailment of its habitat or range; (B) overutilization for commercial, recreational, scientific, or educational purposes; (C) disease or predation; (D) inadequacy of existing regulatory mechanisms; or (E) other natural or manmade factors affecting the species continued existence. Based on our analysis under the five factors, we find that the four central Texas salamanders are primarily threatened by: factors A and D. Therefore, these species qualify for listing, which can only be done by issuing a rule.

The Act requires that the Secretary designate critical habitat for a species, to the maximum extent prudent and determinable, concurrently with making a determination that a species is an endangered or threatened species. Section 4(b)(2) of the Act requires that the Secretary designate critical habitat based upon the best scientific data available, and after taking into consideration the economic impact, the impact on national security, and any other relevant impact of specifying any particular area as critical habitat. Section 4(b)(2) of the Act provides that the Secretary may exclude any area from critical habitat if he determines that the benefits of excluding that area outweigh the benefits of including it in the

designation, unless such an exclusion would result in the extinction of the species. This “weighing” of considerations under section 4(b)(2) of the Act is the next step in the designation process, in which the Secretary may consider particular areas for exclusion from the final designation.

We are preparing an economic analysis.

To ensure that we consider the economic impacts, we are preparing a draft economic analysis of the proposed critical habitat designations. We will use information from this analysis to inform the development of our final designation of critical habitat for these species.

We will seek peer review.

We are seeking comments from independent specialists to ensure that our critical habitat designations are based on scientifically sound data, assumptions, and analyses. We have invited these peer reviewers to comment on our specific assumptions and conclusions in these proposed critical habitat designations. Because we will consider all comments and information we receive during the comment period, our final determinations may differ from this proposal.

Information Requested

We intend that any final action resulting from this proposed rule will be based on the best scientific and commercial data available and be as accurate and as effective as possible. Therefore, we request comments or information from other concerned governmental agencies, Native American tribes, the scientific community, industry, or any other interested parties concerning this proposed rule. We particularly seek comments concerning:

(1) Biological, commercial trade, or other relevant data concerning any threats (or lack thereof) to these species and regulations that may be addressing those threats.

(2) Additional information concerning the historical and current status, range, distribution, and population size of these species, including the locations of any additional populations of these species.

(3) Any information on the biological or ecological requirements of these species, and ongoing conservation measures for these species and their habitats.

(4) Current or planned activities in the areas occupied by the species and possible impacts of these activities on these species.

(5) The reasons why we should or should not designate habitat as “critical habitat” under section 4 of the Act (16 U.S.C. 1531

et seq.

) including whether there are threats to the species from human activity, the degree of which can be expected to increase due to the designation, and whether that increase in threat outweighs the benefit of designation, such that the designation of critical habitat may not be prudent.

(6) Specific information on:

(a) The amount and distribution of the four central Texas salamanders' habitats,

(b) What areas, that are currently occupied by these species, that contain features essential to their conservation,

(c) Special management considerations or protection that may be needed in critical habitat areas we are proposing, including managing for the potential effects of climate change,

(d) What areas not occupied at the time of listing are essential for the conservation of these species and why,

(e) How subterranean populations of these four salamander species are distributed underground, and

(f) The interconnectedness of salamander habitats in terms of hydrology, and whether salamanders are able to move between sites through underground aquifer conduits.

(7) Land use designations and current or planned activities in the subject areas and their possible impacts on the four central Texas salamanders and on proposed critical habitat.

(8) Information on the projected and reasonably likely impacts of climate change on the four central Texas salamanders and proposed critical habitat.

(9) Any probable economic, national security, or other relevant impacts of designating any area that may be included in the final critical habitat designation; in particular, we seek information on any impacts on small entities or families, and the benefits of including or excluding areas that exhibit these impacts.

(10) Whether any specific areas we are proposing for critical habitat designation should be considered for exclusion under section 4(b)(2) of the Act, and whether the benefits of potentially excluding any specific area outweigh the benefits of including that area under section 4(b)(2) of the Act; for example, areas that have a 10(a)(1)(B) permit and habitat conservation plan (HCP) that covers any of these salamanders may be considered for exclusion (potentially including the Four Points HCP that covers Jollyville Plateau salamanders).

(11) Whether we could improve or modify our approach to designating critical habitat in any way to provide for greater public participation and understanding, or to better accommodate public concerns and comments.

Please note that submissions merely stating support for or opposition to the action under consideration without providing supporting information, although noted, will not be considered in making a determination, as section 4(b)(1)(A) of the Act directs that determinations as to whether any species is an endangered or threatenedspecies must be made “solely on the basis of the best scientific and commercial data available.”

You may submit your comments and materials concerning this proposed rule by one of the methods listed in the

ADDRESSES

section. We request that you send comments only by the methods described in the

ADDRESSES

section.

If you submit information via

http://www.regulations.gov,

your entire submission—including any personal identifying information—will be posted on the Web site. If your submission is made via a hardcopy that includes personal identifying information, you may request at the top of your document that we withhold this information from public review. However, we cannot guarantee that we will be able to do so. We will post all hardcopy submissions on

http://www.regulations.gov.

Please include sufficient information with your comments to allow us to verify any scientific or commercial information you include.

Comments and materials we receive, as well as supporting documentation we used in preparing this proposed rule, will be available for public inspection on

http://www.regulations.gov,

or by appointment, during normal business hours, at the U.S. Fish and Wildlife Service, Austin Ecological Services Field Office (see

FOR FURTHER INFORMATION CONTACT

).

Previous Federal Actions

The Austin blind and Salado salamanders were included in nine Candidate Notices of Review (67 FR 40657, June 13, 2002; 69 FR 24876, May 4, 2004; 70 FR 24870, May 11, 2005; 71 FR 53756, September 12, 2006; 72 FR 69034, December 6, 2007; 73 FR 75176, December 10, 2008; 74 FR 57804, November 9, 2009; 75 FR 69222, November 10, 2010; 76 FR 66370, October 26, 2011). The listing priority number has remained at 2 throughout the reviews for both species, indicating that threats to the species were both imminent and high in magnitude. In addition, on May 11, 2004, the Service received a petition from the Center for Biological Diversity to list 225 species we previously had identified as

candidates for listing in accordance with section 4 of the Act, including the Austin blind and Salado salamanders.

The Jollyville Plateau salamander was petitioned to be listed as an endangered species on June 13, 2005, by Save Our Springs Alliance. Action on this petition was precluded by court orders and settlement agreements for other listing actions until 2006. On February 13, 2007, we published a 90-day petition finding (72 FR 6699) in which we concluded that the petition presented substantial information indicating that listing may be warranted. On December 13, 2007, we published the 12-month finding (72 FR 71040) on the Jollyville Plateau salamander, which concluded that listing was warranted, but precluded by higher priority actions. The Jollyville Plateau salamander was subsequently included in all of our annual Candidate Notices of Review (73 FR 75176, December 10, 2008; 74 FR 57804, November 9, 2009; 75 FR 69222, November 10, 2010; 76 FR 66370, October 26, 2011). Throughout the three reviews, the listing priority number has remained at 8, indicating that threats to the species were imminent, but moderate to low in magnitude. On September 30, 2010, the Jollyville Plateau salamander was petitioned to be emergency listed by Save Our Springs Alliance and Center for Biological Diversity. We issued a petition response letter to Save Our Springs Alliance and Center for Biological Diversity on December 1, 2011, which stated that emergency listing a species is not a petitionable action under the Administrative Procedure Act or the Act; therefore, we treat a petition requesting emergency listing solely as a petition to list a species under the Act.

The Georgetown salamander was included in 10 Candidate Notices of Review (66 FR 54808, October 30, 2001; 67 FR 40657, June 13, 2002; 69 FR 24876, May 4, 2004; 70 FR 24870, May 11, 2005; 71 FR 53756, September 12, 2006; 72 FR 69034, December 6, 2007; 73 FR 75176, December 10, 2008; 74 FR 57804, November 9, 2009; 75 FR 69222, November 10, 2010; 76 FR 66370, October 26, 2011). In the 2008 review, the listing priority number was lowered from 2 to 8, indicating that threats to the species were imminent, but moderate to low in magnitude. This reduction in listing priority number was primarily due to the land acquisition and conservation efforts of the Williamson County Conservation Foundation. In addition, the Georgetown salamander was petitioned by the Center for Biological Diversity to be listed as an endangered species on May 11, 2004, but at that time, it was already a candidate species whose listing was precluded by higher priority actions.

Endangered Status for the Four Central Texas Salamanders

Background

It is our intent to discuss below only those topics directly relevant to the proposed listing of the Austin blind salamander, Jollyville Plateau salamander, Georgetown salamander, and Salado salamander as endangered in this section of the proposed rule.

Species Information

All four central Texas salamanders (Austin blind, Jollyville Plateau, Georgetown, and Salado salamanders) are neotenic (do not transform into a terrestrial form) members of the family Plethodontidae. Plethodontid salamanders comprise the largest family of salamanders within the Order Caudata, and are characterized by an absence of lungs (Petranka 1998, pp. 157-158). As neotenic salamanders, they retain external feathery gills and inhabit aquatic habitats (springs, spring-runs, and wet caves) throughout their lives (Chippindale

et al.

2000, p. 1). In other words, all four of these salamanders are entirely aquatic and respirate through gills. Also, all adult salamanders of these four species are about 2 inches (in) (5 centimeters (cm)) long (Chippindale

et al.

2000, pp. 32-42; Hillis

et al.

2001, p. 268).

Each species inhabits water of high quality with a narrow range of conditions (for example, temperature, pH, and alkalinity) maintained by the Edwards Aquifer. All four species depend on this water from the Edwards Aquifer in sufficient quantity and quality to meet their life-history requirements for survival, growth, and reproduction. The Edwards Aquifer is a karst aquifer characterized by open chambers such as caves, fractures, and other cavities that were formed either directly or indirectly by dissolution of subsurface rock formations. Water for the salamanders is provided by infiltration of surface water through the soil or recharge features (caves, faults, fractures, sinkholes, or other open cavities) into the Edwards Aquifer, which discharges from springs as groundwater (Schram 1995, p. 91). The habitat of one species (Austin blind salamander) occurs in the Barton Springs Segment of the Edwards Aquifer, while the habitats of the three other species occur in the Northern Segment of the Edwards Aquifer. The recharge and contributing zones of these segments of the Edwards Aquifer are found in portions of Travis, Williamson, Blanco, Bell, Burnet, Lampasas, Mills, Hays, Coryell, and Hamilton Counties, Texas (Hill Country Foundation 1995, p. 1). The three salamander species that occur in the Northern Segment of the Edwards Aquifer (Jollyville Plateau, Georgetown, and Salado salamanders) have very similar external morphology. Because of this, they were previously believed to be the same species; however, molecular evidence strongly indicates that there is a high level of divergence between the three groups (Chippindale

et al.

2000, pp. 15-16).

The four central Texas salamander species spend varying portions of their life within their surface (in or near spring openings and pools as well as spring runs) and subsurface (within caves or other underground areas within the Edwards Aquifer) habitats. They travel an unknown depth into interstitial spaces (empty voids between rocks) within the spring or streambed substrate that provide foraging habitat and protection from predators and drought conditions (Cole 1995, p. 24; Pierce and Wall 2011, pp. 16-17). They may also use deeper passages of the aquifer that connect to the spring opening (Dries 2011, City of Austin (COA), pers. comm.). This behavior makes it difficult to accurately estimate population sizes, as only salamanders on the surface can be regularly monitored. Therefore, the status of subsurface populations is largely unknown, making it difficult to assess the effects of threats on the subsurface populations and their habitat.

The Austin blind, Jollyville Plateau, Georgetown, and Salado salamanders have much in common. All four species are entirely aquatic throughout each portion of their life cycles and highly dependent on water from the Edwards Aquifer in sufficient quantity and quality to meet their life-history requirements for growth, survival, and reproduction. Although detailed dietary studies are lacking for these four salamander species, their diets are presumed to be similar to other

Eurycea

species, consisting of small aquatic invertebrates such as amphipods, copepods, isopods, and insect larvae [reviewed in COA 2001, pp. 5-6]. The four central Texas salamanders also share similar predators, which include centrarchid fish (carnivorous freshwater fish belonging to the sunfish family), crayfish, and large aquatic insects (Pierce and Wall 2011, pp. 18-20; Bowles

et al.

2006, p. 117; Cole 1995, p. 26). Because eggs are very rarely found on the surface, it is believed that these salamanders deposit their eggs underground for protection (O'Donnell

et al.

2005, p. 18). The detection of

juveniles in all seasons suggests that reproduction occurs year-round (Bendik 2011a, p. 26; Hillis

et al.

2001, p. 273).

Dispersal patterns through streams or aquifers for these four salamander species are relatively unknown. However, one study of other closely related

Eurycea

species in the southeastern portion of central Texas found that populations of salamanders are genetically isolated from one another and neither aquifers nor streams serve as dispersal corridors (Lucas

et al.

2009, pp. 1,315-1,316).

On the other hand, some evidence suggests that the four Texas salamanders may be able to travel some distance through subsurface aquifer conduits. Recent genetic work on the Jollyville Plateau salamander showed evidence of gene flow between sites that are not connected by surface flow (Chippindale 2010, pp. 9, 18-22). This study suggests that central Texas salamanders are regionally isolated, but populations within those regions have some level of dispersal ability through the subsurface habitat. For example, the Austin blind salamander is believed to occur underground throughout the entire Barton Springs complex (Dries 2011, pers. comm.). The spring habitats used by salamanders of the Barton Springs complex are not connected on the surface, so the Austin blind salamander population extends at least 984 feet (ft) (300 meters (m)) underground, as this is the approximate distance between the farthest two outlets within the Barton Springs complex known to be occupied by the species.

Due to the similar life history of the other three

Eurycea

species considered here, it is plausible that populations of these species could also extend this distance through subterranean habitat. Dye-trace studies have demonstrated that some Jollyville Plateau salamander sites located miles apart are connected hydrologically (Hauwert and Warton 1997), but it remains unclear if salamanders are able to travel between those sites. Also, in Salado, a large underground conduit conveys groundwater from the area under the Stagecoach Hotel to Big Boiling Spring (Mahler 2012, U.S. Geological Survey, pers. comm.). Additionally, in Barton Springs, a mark and recapture study failed to document the movement of endangered Barton Springs salamanders (

Eurycea sosorum

) between any of the springs in the Barton Springs complex (Dries 2012, pers. comm.), although this study has only recently begun and is relatively small in scope. In conclusion, there is some evidence that populations could be connected through subterranean habitat, although dispersal patterns and the actual nature of connectivity are largely unknown.

Because the hydrology of central Texas is very complex and information on the hydrology of specific spring sites is largely unknown, we are seeking information on spring hydrology and salamander dispersal during the public comment period (see “Information Requested” above).

Each species is discussed in more detail below.

Austin Blind Salamander

The Austin blind salamander has a pronounced extension of the snout, no external eyes, and weakly developed tail fins. In general appearance and coloration, the Austin blind salamander is more similar to the Texas blind salamander (

Eurycea rathbuni

) that occurs in the Southern Segment of the Edwards Aquifer than its sympatric (occurring within the same range) species, the Barton Springs salamander. The Austin blind salamander has a reflective, lightly pigmented skin with a pearly white or lavender appearance (Hillis

et al.

2001, p. 271). Before the Austin blind salamander was formally described, juvenile salamanders were sighted occasionally in Barton Springs, and thought to be a variation of the Barton Springs salamander. It was not until 2001, that enough specimens were available to formally describe these juveniles as a separate species using morphological and genetic characteristics (Hillis

et al.

2001, p. 267). Given the reduced eye structure of the Austin blind salamander, and the fact that it is rarely seen at the water's surface (Hillis

et al.

2001, p. 267), this salamander is thought to be more subterranean than the surface-dwelling Barton Springs salamander.

The Austin blind salamander occurs in Barton Springs in Austin, Texas. These springs are fed by the Barton Springs Segment of the Edwards Aquifer. This segment covers roughly 155 square miles (mi) (401 square kilometers (km)) from southern Travis County to northern Hays County, Texas (Smith and Hunt 2004, p. 7). It has a storage capacity of over 300,000 acre-feet. The contributing zone for the Barton Springs Segment of the Edwards Aquifer that supplies water to the salamander's spring habitat extends into Travis, Blanco, and Hays Counties, Texas (Ross 2011, p. 3).

The Austin blind salamander is found in three of the four Barton Springs outlets in the City of Austin's Zilker Park, Travis County, Texas: Main (Parthenia) Springs, Eliza Springs, and Sunken Garden (Old Mill or Zenobia) Springs. The Main Springs provides water for the Barton Springs Pool, and is operated by the City of Austin as a public swimming pool. These spring sites have been significantly modified for human use. The area around Main Springs was impounded in the late 1920s to create Barton Springs Pool. Flows from Eliza and Sunken Garden Springs are also retained by concrete structures, forming small pools on either side of Barton Springs Pool (COA 1998, p. 6; Service 2005, p. 1.6-25). The Austin blind salamander has not been observed at the fourth Barton Springs outlet, known as Upper Barton Springs (Hillis

et al.

2001, p. 273). For more information on habitat, see the “Proposed Critical Habitat Designation for the Four Central Texas Salamanders” section of this proposed rule.

From January 1998 to December 2000, there were only 17 documented observations of the Austin blind salamander. During this same time-frame, 1,518 Barton Springs salamander observations were made (Hillis

et al.

2001, p. 273). The abundance of Austin blind salamanders increased slightly from 2002-2006, but fewer observations have been made in more recent years (2009-2010) (COA 2011a, pp. 51-52). When they are observed, Austin blind salamanders occur in relatively low numbers (COA 2011a, pp. 51-52). Most of the Austin blind salamanders that were observed during these surveys were juveniles (less than 1 in (2.5 cm) in total length) (Hillis

et al.

2001, p. 273). Although the technology to safely and reliably mark salamanders for individual recognition has recently been developed (O'Donnell

et al.

2008, p. 3), population estimates for this species have not been undertaken, because surveying within the Edwards Aquifer is not possible at the current time. However, population estimates are possible for aquifer-dwelling species using genetic techniques, and one such study is planned for the Austin blind salamander in the near future (Texas Parks and Wildlife Department (TPWD) 2011a, p. 11).

Jollyville Plateau Salamander

Surface-dwelling populations of Jollyville Plateau salamanders have large, well-developed eyes; wide, yellowish heads; blunt, rounded snouts; dark greenish-brown bodies; and bright yellowish-orange tails (Chippindale

et al.

2000, pp. 33-34). Some cave forms of Jollyville Plateau salamanders exhibit cave-associated morphologies, such as eye reduction, flattening of the head, and dullness or loss of color (Chippindale

et al.

2000, p. 37). Genetic analysis suggests a taxonomic split

within this species that appears to correspond to major geologic and topographic features of the region (Chippindale 2010, p. 2). Chippindale (2010, pp. 5, 8) concluded that the Jollyville Plateau salamander exhibits a strong genetic separation between two lineages within the species: A “Plateau” clade that occurs in the Bull Creek, Walnut Creek, Shoal Creek, Brushy Creek, South Brushy Creek, and southeastern Lake Travis drainages; and a “peripheral” clade that occurs in the Buttercup Creek and northern Lake Travis drainages (Chippindale 2010, pp. 5-8). The study also suggests this genetic separation may actually represent two species (Chippindale 2010, pp. 5, 8). However, a formal, peer-reviewed description of the two possible species has not been published. We therefore do not recognize a separation of the Jollyville Plateau salamander into two species because this split has not been recognized by the scientific community.

The Jollyville Plateau salamander occurs in the Jollyville Plateau and Brushy Creek areas of the Edwards Plateau in Travis and Williamson Counties, Texas (Chippindale

et al.

2000, pp. 35-36; Bowles

et al.

2006, p. 112; Sweet 1982, p. 433). Upon classification as a species, Jollyville Plateau salamanders were known from Brushy Creek and, within the Jollyville Plateau, from Bull Creek, Cypress Creek, Long Hollow Creek, Shoal Creek, and Walnut Creek drainages (Chippindale

et al.

2000, p. 36). Since it was described, the Jollyville Plateau salamander has also been documented within the Lake Creek drainage (O'Donnell

et al.

2006, p. 1). Cave-dwelling Jollyville Plateau salamanders are known from 1 cave in the Cypress Creek drainage and 12 caves in the Buttercup Creek cave system in the Brushy Creek drainage (Chippindale

et al.

2000, p. 49; Russell 1993, p. 21; Service 1999, p. 6; HNTB 2005, p. 60).

The Jollyville Plateau salamander's spring-fed habitat is typically characterized by a depth of less than 1 foot (ft) (0.3 meters (m)) of cool, well oxygenated water (COA 2001, p. 128; Bowles

et al.

2006, p. 118) supplied by the underlying Northern Segment of the Edwards Aquifer (Cole 1995, p. 33). The aquifer that feeds this salamander's habitat is generally small, shallow, and localized (Chippindale

et al.

2000; p. 36, Cole 1995, p. 26). Jollyville Plateau salamanders are typically found near springs or seep outflows and likely require constant temperatures (Sweet 1982, pp. 433-434; Bowles

et al.

2006, p. 117). Salamander densities are higher in pools and riffles and in areas with rubble, cobble, or boulder substrates rather than on solid bedrock (COA 2001, p. 128; Bowles

et al.

2006, pp. 114-116). Surface-dwelling Jollyville Plateau salamanders also occur in subsurface habitat within the underground aquifer (COA 2001, p. 65; Bowles

et al.

2006, p. 118). For more on habitat, see the “Proposed Critical Habitat Designation for the Four Central Texas Salamanders” of this proposed rule.

Some Jollyville Plateau salamander populations have experienced decreases in abundance in recent years. City of Austin survey data indicate that four of the nine sites that were regularly monitored by City of Austin staff between December 1996 and January 2007 had statistically significant declines in salamander abundance over 10 years (O'Donnell

et al.

2006, p. 4). The average number of salamanders counted at each of these 4 sites declined from 27 salamanders counted during surveys from 1996 to 1999 to 4 salamanders counted during surveys from 2004 to 2007. In 2007, monthly mark-recapture surveys were conducted in concert with surface counts at three sites in the Bull Creek watershed (Lanier Spring, Lower Rieblin, and Wheless Spring) over a 6-to-8-month period to obtain surface population size estimates and detection probabilities for each site (O'Donnell

et al.

2008, p. 11). Surface population estimates at Lanier Spring varied from 94 to 249, surface population estimates at the Lower Rieblin site varied from 78 to 126, and surface population estimates at Wheless Spring varied from 187 to 1,024 (O'Donnell

et al.

2008, pp. 44-45). These numbers remained fairly consistent in more recent population estimates for the three sites (Bendik 2011a, p. 22).

Georgetown Salamander

The Georgetown salamander is characterized by a broad, relatively short head with three pairs of bright-red gills on each side behind the jaws, a rounded and short snout, and large eyes with a gold iris. The upper body is generally grayish with varying patterns of melanophores (cells containing brown or black pigments called melanin) and iridophores (cells filled with iridescent pigments called guanine), while the underside is pale and translucent. The tail tends to be long with poorly developed dorsal and ventral fins that are golden-yellow at the base, cream-colored to translucent toward the outer margin, and mottled with melanophores and iridophores. Unlike the Jollyville Plateau salamander, the Georgetown salamander has a distinct dark border along the lateral margins of the tail fin (Chippindale

et al.

2000, p. 38). As with the Jollyville Plateau salamander, the Georgetown salamander has recently discovered cave-adapted forms with reduced eyes and pale coloration (TPWD 2011a, p. 8).

The Georgetown salamander is known from springs along five tributaries (South, Middle, and North Forks; Cowan Creek; and Berry Creek) to the San Gabriel River (Pierce 2011a, p. 2) and from three caves (aquatic, subterranean locations) in Williamson County, Texas. A groundwater divide between the South Fork of the San Gabriel River and Brushy Creek to the south likely creates the division between the ranges of the Jollyville Plateau and Georgetown salamanders (Williamson County 2008, p. 3-34). The Service is currently aware of 16 Georgetown salamander localities. This species has not been observed in recent years at two locations (San Gabriel Spring and Buford Hollow), despite several visual survey efforts to find it (Pierce 2011b,c, Southwestern University, pers. comm.). The current population status is unknown for four sites due to restricted access (Cedar Breaks, Shadow Canyon, Hogg Hollow Spring, and Bat Well). Georgetown salamanders continue to be observed at the remaining 10 sites (Swinbank Spring, Knight Spring, Twin Springs, Hogg Hollow Spring, Cowan Creek Spring, Cedar Hollow, Cobbs Cavern Spring, Cobbs Well, Walnut Spring, and Water Tank Cave) (Pierce 2011c, pers. comm.; Gluesenkamp 2011a, TPWD, pers. comm.). Recent mark-recapture studies suggest a population size of 100 to 200 adult salamanders at Twin Springs, with a similar population estimate at Swinbank Spring (Pierce 2011a, p. 18). Population sizes at other sites are unknown, but visual surface counts result in comparatively low numbers (Williamson County 2008, pp. 3-35). There are numerous other springs in Williamson County that may support Georgetown salamander populations, but private land ownership prevents investigative surveys (Williamson County 2008, pp. 3-35).

Surface-dwelling Georgetown salamanders inhabit spring runs, riffles, and pools with gravel and cobble rock substrates (Pierce

et al.

2010, pp. 295-296). This species prefers larger cobble and boulders to use as cover (Pierce

et al.

2010, p. 295). Salamanders are found within 164 ft (50 m) of a spring opening (Pierce

et al.

2011a, p. 4), but they are most abundant within the first 16.4 ft (5 m) (Pierce

et al.

2010, p. 294). Individuals do not exhibit much movement throughout the year (Pierce

et al.

2010, p. 294). The water chemistry

of Georgetown salamander habitat is constant year-round in terms of temperature and dissolved oxygen (Pierce

et al.

2010, p. 294, Biagas

et al.

in review, p. 8). Little is known about the ecology of Georgetown salamanders that occupy the cave sites (Cobbs Cavern, Bat Well, and Water Tank Cave) where this species is known to occur or the quality and extent of their subterranean habitats. For more on habitat, see the “Proposed Critical Habitat Designation for the Four Central Texas Salamanders” section of this proposed rule.

Salado Salamander

The Salado salamander has reduced eyes compared to other spring-dwelling

Eurycea

species in north-central Texas and lacks well-defined melanophores. It has a relatively long and flat head, and a blunt and rounded snout. The upper body is generally grayish-brown with a slight cinnamon tinge and an irregular pattern of tiny, light flecks. The underside is pale and translucent. The posterior portion of the tail generally has a well-developed dorsal fin, but the ventral tail fin is weakly developed (Chippindale

et al.

2000, p. 42).

The Salado salamander is known historically from four spring sites near the village of Salado, Bell County, Texas: Big Boiling Springs (also known as Main, Salado, or Siren Springs), Lil' Bubbly Spring, Lazy Days Fish Farm Spring, and Robertson Springs (Chippindale

et al.

2000, p. 43; TPWD 2011a, pp. 1-2). These springs bubble up through faults in the Northern Segment of the Edwards Aquifer and associated limestone along Salado Creek (Brune 1975, p. 31). The four spring sites all contribute to Salado Creek. Under Brune's (1975, p. 5) definition, which identifies springs depending on flow, all sites are considered small (4.5 to 45 gallons per minute (17 to 170 liters per minute)) to medium springs (45 to 449 gallons per minute (170 to 1,1700 liters per minute)). Several other spring sites (Big Bubbly Springs, Critchfield Springs, and Anderson Springs) are located downstream from Big Boiling Springs and Robertson Springs. These springs have been surveyed by TPWD periodically since June 2009, but no salamanders have been found (Gluesenkamp 2010, pers. comm.). In August 2009, TPWD discovered a population of salamanders at a new site (Solana Spring #1) farther upstream on Salado Creek in Bell County, Texas (TPWD 2011a, p. 2). Salado salamanders were recently confirmed at two other spring sites (Cistern and Hog Hollow Springs) farther upstream on the Salado Creek in March 2010 (TPWD 2011a, p. 2). In total, the Salado salamander is known from seven springs. A groundwater divide between Salado Creek and Berry Creek to the south likely creates a division between the ranges of the Georgetown and Salado salamander (Williamson County 2008, p. 3-34).

Of the four salamander species, Salado salamanders are observed the least and are therefore less understood. Biologists were unable to observe this species in its type locality (location from which a specimen was first collected and identified as a species) despite over 20 visits to Big Boiling Springs that occurred between 1991 and 1998 (Chippindale

et al.

2000, p. 43). Likewise, TPWD surveyed this site weekly from June 2009 until May 2010, and found one salamander (Gluesenkamp 2010, pers. comm.) at a spring outlet locally referred to as “Lil' Bubbly” located just upstream from Big Boiling Springs. One additional unconfirmed sighting of a Salado salamander in Big Boiling Springs was reported in 2008, by a citizen of Salado, Texas. In 2009, TPWD was granted access to Robertson Springs to survey for the Salado salamander. This species was reconfirmed at this location in February 2010 (Gluesenkamp 2010, pers. comm.). Salado salamander populations appear to be larger at spring sites upstream of the Village of Salado, probably due to the higher quality of the habitat (Gluesenkamp 2011c, pers. comm.). For more on habitat, see the “Proposed Critical Habitat Designation for the Four Central Texas Salamanders” section of this proposed rule.

Summary of Factors Affecting the Species

Section 4 of the Act (16 U.S.C. 1533), and its implementing regulations at 50 CFR part 424, set forth the procedures for adding species to the Federal Lists of Endangered and Threatened Wildlife and Plants. Under section 4(a)(1) of the Act, we may list a species based on any of the following five factors: (A) The present or threatened destruction, modification, or curtailment of its habitat or range; (B) overutilization for commercial, recreational, scientific, or educational purposes; (C) disease or predation; (D) the inadequacy of existing regulatory mechanisms; and (E) other natural or manmade factors affecting its continued existence. Listing actions may be warranted based on any of the above threat factors, singly or in combination. Each of these factors is discussed below.

Factor A. The Present or Threatened Destruction, Modification, or Curtailment of Its Habitat or Range

Habitat modification, in the form of degraded water quality and quantity and disturbance of spring sites, is the primary threat to the four central Texas salamander species. Water quality degradation in salamander habitat has been cited as the top concern in several studies (Chippindale

et al.

2000, pp. 36, 40, 43; Bowles

et al.

2006, pp. 118-119; O'Donnell

et al.

2006, pp. 45-50), because these salamanders spend their entire life cycle in water. All of the species have evolved under natural aquifer conditions both underground and as the water discharges from natural spring outlets. Deviations from that high water quality have detrimental effects on salamander ecology, because the aquatic habitat can be rendered unsuitable for salamanders by changes in water chemistry, quantity, and flow patterns. Substrate modification is also a major concern for the salamander species (COA 2001, pp. 101, 126; Geismar 2005, p. 2; O'Donnell

et al.

2006, p. 34). Unobstructed interstitial space (the space between the rocks) is critical to habitat of all four salamander species, because it provides cover from predators and habitat for macroinvertebrate prey items. When the interstitial spaces become compacted or filled with fine sediment, the amount of available foraging habitat and protective cover for salamanders is reduced (Welsh and Ollivier 1998, p. 1,128).

Threats to the habitat of the four central Texas salamanders may target only the surface habitat, only the subsurface habitat, or both habitat types. For example, substrate modification degrades the surface springs and spring-runs but does not impact the subsurface environment, while water quality degradation impacts both the surface and subsurface habitats. Because of their ability to retreat to the subsurface habitat, the four central Texas salamander species may be able to persist through surface habitat degradation. For example, drought conditions are common to the region, and these salamanders' ability to retreat underground may be an evolutionary adaptation to such natural conditions (Bendik 2011a, pp. 31-32). However, we do not fully understand the relative importance of the surface and subsurface habitats to salamander populations. The best available scientific evidence suggests that surface habitats are important for prey availability and individual growth. Prey availability for carnivores is low underground due to the lack of sunlight

and primary production (Hobbs and Culver 2009, p. 392). In addition, length measurements taken during a City of Austin mark-recapture study at Lanier Spring demonstrated that Jollyville Plateau salamanders had negative growth during a 10-month period of retreating to the subsurface from 2008 to 2009 (Bendik 2011b, COA, pers. comm.). Therefore, threats to surface habitat at a given site may not extirpate any populations of these salamander species, but this type of habitat degradation may severely limit population growth and increase the species' overall risk of extinction from other threats.

The majority of the discussion below under Factor A focuses on evaluating the nature and extent of stressors related to urbanization within the watershed, the primary source of water quality degradation. Additionally, other sources of habitat destruction and modification will be addressed. These include physical habitat modification from human activities and feral hogs, and environmental events, such as flooding and drought.

Urbanization Within the Watershed

The ranges of the four salamander species reside within increasingly urbanized areas of Travis, Williamson, and Bell Counties that are experiencing rapid human population growth. For example, the population of the City of Austin grew from 251,808 people in 1970, to 656,562 people in 2000. By 2007, the population had grown to 735,088 people (COA 2007a, p. 1). This represents a 192 percent increase over the 37-year period. The human population within the City of Georgetown, Texas, was 28,339 in 2000, and increased to 47,380 by January 2008 (City of Georgetown 2008, pp. 3.3-3.5). The human population is expected to exceed 225,000 by 2033 (City of Georgetown 2008, p. 3.5), which would be a 375 percent increase over a 33-year period. Population projections from the Texas State Data Center (2008, p. 1) estimate that Travis County will increase in population from 812,280 in 2000, to 1,498,569 in 2040. This would be an 84 percent increase in the human population size over this 40-year period. The Texas State Data Center also estimates an increase in human population in Williamson County from 249,967 in 2000, to 1,742,619 in 2040. This would represent a 597 percent increase over a 40-year timeframe. The human population is not increasing as rapidly in the range of the Salado salamander, but growth is occurring. Population projections from the Texas State Data Center (2009, p. 19) estimate that Bell County will increase in population from 237,974 in 2000, to 397,741 in 2040, a 67 percent increase over the 40-year period. By comparison, the national United States' population is expected to increase from 310,233,000 in 2010, to 405,655,000 in 2040, which is about a 24 percent increase over the 30-year period (U.S. Census Bureau 2012, p. 1). Growing human populations increase demand for residential and commercial development, drinking water supply, wastewater disposal, flood control, and other municipal goods and services that alter the environment, often degrading salamander habitat by changing hydrologic regimes, and affecting the quantity and quality of water resources.

As development increases within the watersheds, more opportunities exist for the detrimental effects of urbanization to impact salamander habitat. Urban development upstream of salamander habitat leads to various stressors on spring systems, including increased flow velocities, increased sedimentation, increased contamination, changes in stream morphology and water chemistry, and decreases in groundwater recharge.

Several researchers have examined the negative impact of urbanization on stream salamander habitat by making connections between salamander abundances and levels of development within the watershed. In 1972, Orser and Shure (p. 1,150) were among the first biologists to show a decrease in stream salamander density with increasing urban development. A similar relationship between salamanders and urbanization was found in North Carolina (Price

et al.

2006, pp. 437-439; Price

et al.

2012, p. 198), Maryland, and Virginia (Grant

et al.

2009, pp. 1,372-1,375). In central Texas, Bowles

et al.

(2006, p. 117) found lower Jollyville Plateau salamander densities in tributaries with developed watersheds as compared to tributaries with undeveloped watersheds. Developed tributaries also had higher concentrations of chloride, magnesium, nitrate-nitrogen, potassium, sodium, and sulfate (Bowles

et al.

2006, p. 117). Several biologists have concluded that urbanization is one of the largest threats to the future survival of central Texas salamanders (Bowles

et al.

2006, p. 119; Chippindale and Price 2005, pp. 196-197).

Willson and Dorcas (2003, pp. 768-770) demonstrated that to assess the impact of urbanization on aquatic salamanders, it is important to examine development within the entire watershed as opposed to areas just adjacent to the stream. For example, urban development within the drainage areas of Austin blind and Jollyville Plateau salamander spring sites has included residential and commercial structures, golf courses, and the associated roads and utility pipelines (Cole 1995, p. 28; COA 2001, pp. 10-12).

Because detrimental effects due to urbanization are occurring to the salamanders' habitats now, and we expect those effects to increase in the future, we consider urbanization to be a threat to each of the species. We discuss below how each source of the stressors of urbanization causes threats to the Austin blind, Jollyville Plateau, Georgetown, and Salado salamanders' habitats. These sources of impacts from urbanization include impervious cover and stormwater runoff, land application contaminants, hazardous material spills, construction activities, and water quantity reduction.

Impervious Cover and Stormwater Runoff

Impervious cover is any surface material, such as roads, rooftops, sidewalks, patios, paved surfaces, or compacted soil, that prevents water from filtering into the soil (Arnold and Gibbons 1996, p. 244). Once natural vegetation in a watershed is replaced with impervious cover, rainfall is converted to surface runoff instead of filtering through the ground (Schueler 1991, p. 114).

As urbanization increases due to human population growth within the watersheds of salamander habitat, levels of impervious cover will rise. Various levels of impervious cover within watersheds have been cited as having detrimental effects to water quality within streams. The threshold of measurable degradation of stream habitat and loss of biotic integrity consistently occurs with 6 to 15 percent impervious cover in contributing watersheds (Bowles

et al.

2006, p. 111; Miller

et al.

2007, p. 74). A review of relevant literature by Schueler (1994, pp. 100-102) indicates that stream degradation occurs at impervious cover of 10 to 20 percent, a sharp drop in habitat quality is found at 10 to 15 percent impervious cover, and watersheds above 15 percent are consistently classified as poor, relative to biological condition. Schueler (1994, p. 102) also concluded that even when water quality protection practices are widely applied, an impervious cover level of 35 to 60 percent exceeds a threshold beyond which water quality conditions that existed before development occurred cannot be maintained.

Increases in impervious cover resulting from urbanization cause measurable water quality degradation (Klein 1979, p. 959; Bannerman

et al.

1993, pp. 251-254, 256-258; Center for Watershed Protection 2003, p. 91). Stressors from impervious cover have demonstrable impacts on biological communities within streams. Schueler (1994, p. 104) found that sites receiving runoff from high impervious cover drainage areas had sensitive aquatic macroinvertebrate species replaced by species more tolerant of pollution and hydrologic stress (high rate of changes in discharges over short periods of time). In an analysis of 43 North Carolina streams, Miller

et al.

(2007, pp. 78-79) found a strong negative relationship between impervious cover and the abundance of larval southern two-lined salamanders (

Eurycea cirrigera

). Impervious cover degrades salamander habitat in three ways: (1) Introducing and concentrating contaminants in stormwater runoff, (2) increasing sedimentation, and (3) altering the natural flow regime of streams.

Impervious Cover Analysis

To calculate impervious cover within the watersheds occupied by the four central Texas salamander species, we used the Watershed Boundary Dataset (USGS 2012, p. 1) to delineate the watersheds where these species are known to occur along with the 2006 National Land Cover Dataset (MRLC 2012, p. 1). The Watershed Boundary Dataset is a nationally consistent watershed dataset developed by the U.S. Geological Survey (USGS) that is subdivided into 12-digit hydrologic unit codes, which are the smallest (or finest scale) of the hydrologic units available. Each of the 12-digit hydrologic unit codes represents part or all of a surface drainage basin or a combination of drainage basins, also referred to in the Watershed Boundary Dataset as “watersheds.” The 2006 National Land Cover Dataset (the most recent of the national land cover datasets) was developed by the Multi-Resolution Land Characteristics Consortium to provide 30-meter spatial resolution estimates for tree cover and impervious cover percentages within the contiguous United States.

We identified 15 of the watersheds delineated within the Watershed Boundary Dataset as being occupied by one of the four central Texas salamander species. The Jollyville Plateau salamander occurs within six watersheds (Bull Creek, Cypress Creek, Lake Creek, South Brushy Creek, Town Lake, and Walnut Creek). The Austin blind salamander occurs within one watershed (Lake Austin). The Georgetown salamander occurs within six watersheds (Dry Berry Creek, Lake Georgetown, Lower Berry Creek, Lower South Fork San Gabriel River, Middle Fork San Gabriel River, and Smith Branch San Gabriel River). The Salado salamander occurs within two watersheds (Buttermilk Creek and Mustang Creek).

An impervious cover value (0 to 100 percent) is assigned for each 30-meter pixel within the 2006 National Land Cover Dataset. Using these values, we calculated the overall average value (percentage) for each watershed identified. We also identified three categories of impervious cover for each pixel: (1) 0 percent impervious cover (no impervious cover was identified within the 30-meter pixel), (2) 1 to 15 percent impervious cover (between 1 and 15 percent of the 30-meter pixel was identified as impervious cover), and (3) greater than 15 percent impervious cover (more than 15 percent of the 30-meter pixel was identified as impervious cover). For each watershed, we then calculated the percentage of pixels that fell into each of these three categories. These percentages are presented in Table 1.

Table 1—Impervious Cover Estimates

Salamander species

(total number of known sites)

Watershed

Number of

salamander

sites

Categories of impervious cover (IC) percentage

0% IC

1-15% IC

>15% IC

Average

impervious cover (IC)

percentage

Jollyville Plateau salamander (92)

Bull Creek

64

61

14

25

12.00

Cypress Creek

11

79

9

12

5.72

Lake Creek

3

43

17

40

21.35

South Brushy Creek

9

58

17

24

12.52

Town Lake

4

11

30

59

34.32

Walnut Creek

1

34

17

50

28.03

Austin blind salamander (3)

Lake Austin

3

54

24

24

11.58

Georgetown salamander (16)

Dry Berry Creek

2

92

7

1

0.59

Lake Georgetown

6

88

11

2

0.76

Lower Berry Creek

2

73

10

17

3.03

Lower South Fork San Gabriel River

1

84

11

6

2.77

Middle Fork San Gabriel River

4

77

11

12

2.41

Smith Branch San Gabriel River

1

61

20

19

9.60

Salado salamander (7)

Buttermilk Creek

3

95

5

1

0.31

Mustang Creek

4

92

7

2

0.91

We also identified areas within each watershed that we knew to be managed as open space. Open space includes lands set aside for either low-use recreation or wildlife preserves. The protection of open space helps preserve the quality of water, which is an important component of salamander surface habitat. Thus, we considered the amount and location of managed open space, and the potential water quality benefits they provide to salamander surface habitat during our analysis of threats caused by impervious cover within each watershed.

The six watersheds within the Jollyville Plateau salamander's range have overall average impervious cover estimates ranging from approximately 6 percent (Cypress Creek) to 34 percent (Town Lake). The majority (64) of the 92 known Jollyville Plateau salamander sites are located within the Bull Creek watershed, which has an overall average impervious cover estimate of 12 percent. When average impervious cover is between 10 and 15 percent within a watershed, sharp declines in aquatic habitat quality are likely to occur (Schueler 1994, pp. 100-102).

However, a substantial portion of the land area categorized as open space and protected as part of the Balcones

Canyonlands Preserve is located within the Bull Creek watershed. The Balcones Canyonlands Preserve is managed under the terms and conditions of a regional habitat conservation plan (HCP) (the Balcones Canyonlands Conservation Plan HCP) jointly held by the City of Austin and Travis County as mitigation lands issued under the authority of an Endangered Species Act section 10(a)(1)(B) permit for the protection of endangered birds and karst invertebrates. A number of cooperating partners own and manage lands dedicated to the Balcones Canyonlands Preserve, including several private landowners, the Lower Colorado River Authority, the Nature Conservancy of Texas, and the Travis Audubon Society. Although the permit that created the Balcones Canyonlands Preserve did not include the Jollyville Plateau salamander, the Balcones Canyonlands Preserve land management strategies help maintain water quality within salamander habitats on lands within the preserve. Nonetheless, the City of Austin has reported significant declines in Jollyville Plateau salamander abundance at one of their Jollyville Plateau salamander monitoring sites within Bull Creek (O'Donnell

et al.

2006, p. 45), even though our analysis found that 61 percent of the land within this watershed has 0 percent impervious cover. The location of this monitoring site is within a large preserved tract. However, the headwaters of this drainage are outside the preserve, and the development in this area increased sedimentation downstream and impacted salamander habitat in the preserved tract.

The Cypress Creek watershed is the least developed of all of the watersheds within the Jollyville Plateau salamander's range, and much of it is extensively covered by lands that are managed as open space. The vast majority of this open space is part of the Balcones Canyonlands Preserve. There are 11 spring sites known to be occupied by the Jollyville Plateau salamander within this watershed. Seven of these sites are located directly within or downstream from areas dominated by impervious surfaces. The 2006 National Land Cover Dataset data indicated that 12 percent of the 30-m pixels in the Cypress Creek watershed have impervious cover of 15 percent or more and 9 percent of the 30-m pixels have impervious cover between 1 and 15 percent.

The other watersheds within the Jollyville Plateau salamander's range have impervious cover levels that may lead to water quality declines within salamander surface habitat (Schueler 1994, pp. 100-102). Nine sites known to be occupied by Jollyville Plateau salamanders are located within the South Brushy Creek watershed, which has an overall average impervious cover estimate of 13 percent and very little managed open space. Again, when average impervious cover is between 10 and 15 percent, sharp declines in aquatic habitat quality are likely to occur (Schueler 1994, pp. 100-102).

The Lake Creek watershed with three known salamander locations and the Walnut Creek watershed with one known salamander location are estimated to have 21 percent and 28 percent impervious cover, respectively. The Lake Creek watershed has two tracts (143 ac (58 ha) and 95 ac (38 ha)) of managed open space along with two smaller preserve areas and several municipal parks. Given their small size in relation to the size of the watershed, it is unknown if these areas provide any water quality benefits for salamander surface habitat. The single Jollyville Plateau salamander location within the Walnut Creek watershed is located on a 53-ac (21-ha) park that is situated directly adjacent to a residential development. There are two small (14 ac (6 ha) and 67 ac (27 ha)) municipal parks located upstream from this site. However, the 2006 National Land Cover Dataset data indicated that 50 percent of the 30-m pixels in the Walnut Creek watershed have impervious cover of 15 percent or more and 17 percent of the 30-m pixels have impervious cover between 1 and 15 percent. Because this watershed is extensively covered by impervious surfaces, it is unlikely that these managed open spaces provide adequate water quality for the Jollyville Plateau salamander. Salamander counts at the Walnut Creek location have been low. Although surveys are conducted four times a year, no salamanders were observed from 2006 to 2009, and only six individuals were observed in 2010 (Bendik 2011a, p. 13).

The Town Lake watershed is the most developed of all of the watersheds within the Jollyville Plateau salamander's range. Four Jollyville Plateau salamander sites are located within the Town Lake watershed, which has an estimated 30 percent of its 30-m pixels within the 1 to 15 percent impervious cover category and 59 percent of its 30-m pixels within the greater than 15 percent impervious cover category. We could not identify any parcels of land that are managed as open space within the Town Lake watershed.

The Austin blind salamander occurs within only one of the watersheds (Lake Austin) delineated within the Watershed Boundary Dataset. The Lake Austin watershed was estimated to have an overall average impervious cover estimate of 12 percent. Although each of the three spring sites where this species is known to occur are located within a park managed by the City of Austin, the water quality within the salamander's habitat can be influenced by development throughout the watershed. The impervious cover within the Lake Austin watershed, which is an indicator of development intensity within the area, is within the range that can lead to water quality declines in aquatic habitats (Schueler 1994, pp. 100-102). Some Balcones Canyonlands Preserve lands are located within the Lake Austin watershed, which likely contribute some water quality benefits to surface flow. However, the Austin blind salamander is, in large part, a subterranean species. Therefore, water quality within this species' habitat can be influenced by land use throughout the recharge zone of the Barton Springs Segment of the Edwards Aquifer.

The Lower Colorado River Authority (LCRA 2002, pp. 3-54—3-55) conducted a water supply study of the recharge and contributing zone areas within the Barton Springs Segment of the Edwards Aquifer that examined the amount of impervious cover within the local area. The eight watersheds within the area had a range of impervious cover from 3 percent to 29 percent in 2000. The projected impervious cover limits for the same eight watersheds in 2025 ranged from 5 percent to 32 percent (LCRA 2002, pp. 4-12—4-13). The two watersheds, Williamson Creek and Sunset Valley Creek (a tributary to Williamson Creek), with the highest percentage of impervious cover (16 and 29 percent, respectively) are also the second and third closest to Barton Springs (LCRA 2002, pp. 4-12—4-13).

The six watersheds within the Georgetown salamander's range have overall average impervious cover estimates ranging from 0.59 percent (Dry Berry Creek) to about 10 percent (Smith Branch San Gabriel River). The overall average impervious cover estimates for each of the six watersheds are below the levels that have been shown to lead to sharp water quality declines in aquatic habitats (Schueler 1994, pp. 100-102). Two (Cobbs Spring and Cobbs Spring Well) of the 16 sites known to be occupied by the Georgetown salamander occur in the headwaters of the Dry Berry Creek watershed, which has an overall average impervious cover estimate of 0.59 percent.

Six spring sites known to be occupied by Georgetown salamander are located within the Lake Georgetown watershed.

This watershed also has one of the least overall average impervious cover estimates (0.76 percent) of the six watersheds within the Georgetown salamander's range. These six sites, along with three of the four spring sites known to be occupied by the Georgetown salamander in the Middle Fork San Gabriel River watershed (with an overall average impervious cover estimate of about 2 percent) and the only known Georgetown salamander site within the Lower South Fork San Gabriel River watershed (with an overall average impervious cover estimate of about 3 percent), are located upstream from the urbanized areas associated with the City of Georgetown. Therefore, these sites are likely not as affected by water quality degradation currently as those spring sites occupied by the Georgetown salamander within the highly urbanized areas of the City of Georgetown.

We identified two tracts of land managed specifically as open space within the Georgetown salamander's range. Williamson County manages a 64-ac (26-ha) conservation easement at Cobbs Cavern and owns the 145-ac (59-ha) Twin Springs Preserve. The Twin Springs preserve contains one Georgetown salamander site. While the Cobbs Cavern conservation easement does not include the Cobbs Spring or Cobbs well site, it does contain land in the watershed for these sites. Despite the protection of these two tracts, water quality at these sites can be influenced by activities occurring throughout the recharge zone. Without more managed open space within this species' range, it is unlikely that water quality within the Georgetown salamander's surface habitat will be protected as development continues in these watersheds into the future.

Four of the 16 sites known to be occupied by the Georgetown salamander are located in areas identified as having impervious cover estimates (either in the 1 to 15 percent impervious cover category or the greater than 15 percent impervious cover category) within the range that can lead to water quality declines (10 to 15 percent) or poor water quality relative to biological condition (greater than 15 percent) in aquatic habitats (Schueler 1994, pp. 100-102). These include one site in the Middle Fork San Gabriel River watershed, the only occupied site within the Smith Branch San Gabriel River watershed (with an overall average impervious cover estimate of about 10 percent), and the two occupied sites within the Lower Berry Creek watershed (with an overall average impervious cover estimate of about 3 percent). Although the overall average impervious cover estimate within Lower Berry Creek watershed is below the level that has been shown to lead to water quality declines in aquatic habitats (Schueler 1994, pp. 100-102), 17 percent of the watershed has greater than 15 percent impervious cover. These two Georgetown salamander sites are located in the most developed area of this watershed. As such, these sites are vulnerable to water quality degradation caused by pollutants associated with highly urbanized areas.

The Salado salamander occurs within two of the watersheds delineated within the Watershed Boundary Dataset. Buttermilk Creek and Mustang Creek watersheds have overall average impervious cover estimates of 0.31 percent and 0.91 percent, respectively. Although these impervious cover levels are well below that which are likely to lead to water quality declines in aquatic habitats (Schueler 1994, pp. 100-102), three of the seven springs sites known to be occupied by the Salado salamander are directly within urbanized habitats in the Mustang Creek watershed (within the Village of Salado), and therefore, may be more susceptible to spills of hazardous materials and pollutants from roads that are close to locations where salamanders are known to occur.

Four spring sites known to be occupied by Salado salamanders are upstream from the urbanized areas associated with the Village of Salado. Three of these spring sites are located within the Buttermilk Creek watershed on an approximately 8,126-ac (3,288-ha) ranch that is privately owned and almost entirely undeveloped. Another spring site known to be occupied by the Salado salamander within the Mustang Creek watershed is located on another privately owned and almost entirely undeveloped ranch that is approximately 827 ac (335 ha) in size. Both ranches are located upstream of the impervious cover areas associated with the Village of Salado and entirely within the recharge zone of the Northern Segment of the Edwards Aquifer. Although impervious cover is not currently a threat to these upstream sites, a significant portion of the recharge zone extends to areas off of these properties and spring water quality can be impacted by activities occurring some distance away.

We could not identify any large tracts of lands managed specifically as open space within the Salado salamander's range, particularly upstream of sites where this species is known to occur. In addition, there are no agreements in place to preserve or manage the above-mentioned properties for the benefit of the Salado salamander or its surface habitat. Without these, it is unlikely that water quality within the Salado salamander's surface habitat will be protected if development occurs in these watersheds in the future.

Although the data for this level of the impervious cover analysis were derived using the finest scale hydrologic units readily available in the Watershed Boundary Dataset, they offer no reference to the location of salamander-occupied spring sites in relation to the location of impervious cover within the watersheds. Therefore, impervious cover occurring within each watershed may not necessarily be an indicator of how much impervious cover is impacting water quality within known salamander sites because this analysis does not take into account whether the salamander sites are found upstream or downstream of impervious surfaces associated with developed areas. Moreover, because the most recent impervious cover estimates available within the National Land Cover Dataset were provided from 2006 data, more impervious cover could be present within the watersheds than are indicated in our analysis. By mapping the spring sites where salamanders are known to occur over the 2006 National Land Cover Dataset impervious cover data layer, we can generally discuss which sites may currently be affected by water quality degradation due to their location within the three impervious cover categories mentioned above and identified in Table 1.

To provide a general indication of how much impervious cover may be influencing surface water quality at individual salamander sites, we used 2010 aerial photos to visually estimate the amount of impervious cover upstream of each site known to be occupied by the Jollyville Plateau, Georgetown, or Salado salamander. By visually examining the aerial photos from 2010, we classified the areas within each tributary watershed upstream from each known salamander site into one of four categories (that represent approximations of impervious cover levels). We defined these categories as follows: (1) None (a tributary watershed with no visible impervious cover), (2) low (a tributary watershed with what appeared to be less than 10 percent impervious cover), (3) moderate (a tributary watershed with what appeared to be impervious cover between 10 and 30 percent), and (4) high (a tributary watershed with what appeared to be greater than 30 percent impervious cover). A summary of the number of salamander sites for each of these three species found to be within

the impervious cover categories is provided below (Table 2).

Table 2—Impervious Cover Estimates Upstream of Known Salamander Locations

Salamander species

Number of

salamander sites

Number of sites with impervious cover levels

None

Low

Moderate

High

Jollyville Plateau salamander

92

17

6

21

48

Georgetown salamander

16

4

9

2

1

Salado Salamander

7

2

4

0

1

The Austin blind salamander was not considered in the analysis of impervious cover upstream of its known sites, as it primarily occurs below the surface and is more likely to be impacted by water quality changes due to impervious cover throughout the Edward Aquifer's recharge zone. Using the 2006 National Land Cover Database, we determined that the recharge zone of the Barton Springs Segment of the Edwards Aquifer had an overall average impervious cover level of 5.87 percent. However, at least 12 percent of the recharge zone has greater than 15 percent impervious cover.

Contaminants in Stormwater Runoff

Urban environments are host to a variety of human activities that generate many types of point source (“end of pipe”) and non-point source (coming from many diffuse sources) contaminants. These sources of contaminants, when combined, often degrade nearby waterways and aquatic resources within the watershed. Urban contaminants commonly detected in stormwater include elevated levels of suspended solids, nutrients, trace metals, pesticides, and coliform bacteria. Similarly, various industrial and municipal activities result in the discharge of treated wastewater or unintentional release of industrial contaminants as point source pollution.

Stormwater runoff carries these contaminants into stream systems (Bannerman

et al.

1993, pp. 251-254, 256-258; Schueler 1994, p. 102; Barrett and Charbeneau 1996, p. 87; Center for Watershed Protection 2003, p. 91). Amphibians, especially their eggs and larvae (which are usually restricted to a small area within an aquatic environment), are sensitive to many different aquatic pollutants (Harfenist

et al.

1989, pp. 4-57). Contaminants found in aquatic environments, even at sublethal concentrations, may interfere with a salamander's ability to develop, grow, or reproduce (Burton and Ingersoll 1994, pp. 120, 125). Central Texas spring salamanders are particularly vulnerable to contaminants, because they have evolved under very stable environmental conditions, remain aquatic throughout their entire life cycle, have highly permeable skin, have severely restricted ranges, and cannot escape contaminants in their environment (Turner and O'Donnell 2004, p. 5). In addition, macroinvertebrates, such as small freshwater crustaceans, that aquatic salamanders feed on are especially sensitive to water pollution (Phipps

et al.

1995, p. 282; Miller

et al.

2007, p. 74). Studies in the Bull Creek watershed in Austin, Texas, found a loss of some sensitive macroinvertebrate species, potentially due to contaminants of nutrient enrichment and sediment accumulation (COA 2001, p. 15; COA 2010a, p. 16).

Both nationally and locally, consistent relationships between impervious cover and water quality degradation through contaminant loading have been documented. In a study of contaminant loads from various land use areas in Austin, stormwater runoff loads were found to increase with increasing impervious cover (COA 1990, pp. 12-14). This study also found that contaminant loading rates of the more urbanized watersheds were higher than those of the small suburban watersheds. Soeur

et al.

(1995, p. 565) determined that stormwater contaminant loading positively correlated with development intensity in Austin. In a study of 38 small watersheds in the Austin area, 7 different contaminants were found to be positively correlated with impervious cover (COA 2006, p. 35). Using stream data from 1958 to 2007 at 24 Austin-area sites, Glick

et al.

(2009, p. 9) found that the City of Austin's water quality index had a strong negative correlation with impervious cover.

Polycyclic aromatic hydrocarbons (PAHs) are a common form of aquatic contaminants in urbanized areas that could potentially affect salamanders, their habitat, or their prey. This form of pollution can originate from petroleum products, such as oil or grease, or from atmospheric deposition as a byproduct of combustion (for example, vehicular combustion). These pollutants accumulate over time on impervious cover, contaminating water supplies through urban and highway runoff (Van Metre

et al.

2000, p. 4,067; Albers 2003, pp. 345-346). The main source of PAH loading in Austin-area streams is parking lots with coal tar emulsion sealant, even though this type of lot only covers 1 to 2 percent of the watersheds (Mahler

et al.

2005, p. 5565). A recent analysis of the rate of wear on coal tar lots revealed that the sealcoat wears off relatively quickly and contributes more to PAH loading than previously thought (Scoggins

et al.

2009, p. 4914).

Petroleum and petroleum byproducts can adversely affect living organisms by causing direct toxic action, altering water chemistry, reducing light, and decreasing food availability (Albers 2003, p. 349). Exposure to PAHs at levels found within the Jollyville Plateau salamander's range can cause impaired reproduction, reduced growth and development, and tumors or cancer in species of amphibians, reptiles, and other organisms (Albers 2003, p. 354). Coal tar pavement sealant slowed hatching, growth, and development of a frog (

Xenopus laevis

) in a laboratory setting (Bryer

et al.

2006, pp. 244-245). High concentrations of PAHs from coal tar sealant negatively affected the righting ability (amount of time needed to flip over after being placed on back) of adult eastern newts (

Notophthalmus viridescens

) and may have also damaged the newt's liver (Sparling

et al.

2009, pp. 18-20). For juvenile spotted salamanders (

Ambystoma maculatum

), PAHs reduced growth in the lab (Sparling

et al.

2009, p. 28). In a lab study using the same coal tar sealant once used by the City of Austin, Bommarito

et al.

(2010, pp. 1151-1152) found that spotted salamanders displayed slower growth rates and diminished swimming ability when exposed to PAHs. PAHs are also known to cause death, reduced survival, altered physiological function, inhibited reproduction, and changes in

community composition of freshwater invertebrates (Albers 2003, p. 352).

Limited sampling by the City of Austin has detected PAHs at concentrations of concern at multiple sites within the range of the Jollyville Plateau salamander. Most notable were the elevated levels of nine different PAH compounds at the Spicewood Springs site in the Shoal Creek drainage area (O'Donnell

et al.

2005, pp. 16-17). This is also one of the sites where salamanders have shown a significant decline in abundance during the City of Austin's long-term monitoring studies (O'Donnell

et al.

2006, p. 47). Another study found several PAH compounds in seven Austin-area streams, including Barton, Bull, and Walnut Creeks, downstream of coal tar sealant parking lots (Scoggins

et al.

2007, p. 697). Sites with high concentrations of PAHs (located in Barton and Walnut Creeks) had fewer macroinvertebrate species and lower macroinvertebrate density (Scoggins

et al.

2007, p. 700). This form of contamination has also been detected at Barton Springs, which is the Austin blind salamander's habitat (COA 1997, p. 10). Because PAHs can adversely affect salamanders, PAHs have been found in the range of the species, and we expect an increase of this contaminant in the future in conjunction with the increase of urbanization, we consider contamination from PAHs to be a threat to the continued existence of all four central Texas salamanders now and in the future.

Conductivity is a measure of the ability of water to carry an electrical current and can be used to approximate the concentration of dissolved inorganic solids in water that can alter the internal water balance in aquatic organisms, affecting the four central Texas salamanders' survival. As ion concentrations such as chlorides, sodium, sulfates, and nitrates rise, conductivity will increase. These compounds are the chemical products, or byproducts, of many common pollutants that originate from urban environments (Menzer and Nelson 1980, p. 633), which are often transported to streams via stormwater runoff from impervious cover. Measurements by the City of Austin between 1997 and 2006 found that conductivity averaged between 550 and 650 microsiemens per centimeter (μS cm

−1

) at rural springs with low or no development and averaged between 900 and 1000 μS cm

−1

at monitoring sites in watersheds with urban development (O'Donnell

et al.

2006, p. 37). The City of Austin also found increasing ions with increasing impervious cover at four Jollyville Plateau salamander sites (Herrington

et al.

2007, p. 13). These results indicate that developed watersheds contribute to higher levels of water contaminants in salamander habitats.

High conductivity has been associated with declining salamander abundance. For example, three of the four sites with statistically significant declining Jollyville Plateau salamander abundance from 1997 to 2006 are cited as having high conductivity readings (O'Donnell

et al.

2006, p. 37). Similar correlations were shown in studies comparing developed and undeveloped sites from 1996 to 1998 (Bowles

et al.

2006, pp. 117-118). This analysis found significantly lower numbers of salamanders and significantly higher measures of specific conductance at developed sites as compared to undeveloped sites (Bowles

et al.

2006, pp. 117-118). Tributary 5 of Bull Creek has had an increase in conductivity, chloride, and sodium and a decrease in invertebrate diversity from 1996 to 2008 (COA 2010a, p. 16). Only one Jollyville Plateau salamander has been observed here from 2009 to 2010 in quarterly surveys (Bendik 2011a, p. 16). Poor water quality, as measured by high specific conductance and elevated levels of ion concentrations, is cited as one of the likely factors leading to statistically significant declines in salamander abundance at the City of Austin's long-term monitoring sites (O'Donnell

et al.

2006, p. 46).

In an analysis performed by the City of Austin (Turner 2005a, p. 6), significant changes over time were reported for several chemical constituents and physical parameters in Barton Springs Pool, which could be attributed to impacts from watershed urbanization. Conductivity, turbidity, sulfates, and total organic carbon have increased while the concentration of dissolved oxygen has decreased (Turner 2005a, pp. 8-17). The significance and presence of trends in other pollutants were variable depending on flow conditions (baseflow vs. stormflow, recharge vs. non-recharge) (Turner 2005a, p. 20). A similar analysis by Herrington and Hiers (2010, p. 2) examined water quality at Barton Springs Pool and other Barton Springs outlets where Austin blind salamanders are found (Sunken Gardens and Eliza Springs) over a general period of the mid-1990s to the summer of 2009. Herrington and Hiers (2010, pp. 41-42) found that dissolved oxygen decreased over time in the Barton Springs Pool, while conductivity and nitrogen increased. However, this decline in water quality was not seen in Sunken Gardens Spring or Elisa Spring (Herrington 2010, p. 42). A separate analysis found that ions such as chloride and sulfate increased in Barton Creek despite the enactment of city-wide water quality control ordinances (Turner 2007, p. 7). Overall, these studies indicate a long-term trend of water quality degradation at Barton Springs over a 34-year period (1975 to 2009).

In summary, there are many different types of contaminants found in stormwater runoff that can have detrimental effects on the four central Texas salamanders. Impervious cover increases the transport of contaminants common in urban environments, and we expect this detrimental effect to increase in the future with increased urbanization. Therefore, the current existence and future increase of contaminants in stormwater runoff is a significant threat to all four central Texas salamanders' surface and subsurface habitats throughout their ranges. However, due to the relatively low levels of impervious cover in its range, the Salado salamander is currently, and anticipated to be, less affected.

Sedimentation from Stormwater Runoff

Elevated mobilization of sediment (mixture of silt, sand, clay, and organic debris) occurs as a result of increased velocity of water running off impervious surfaces (Schram 1995, p. 88; Arnold and Gibbons 1996, pp. 244-245). Increased rates of stormwater runoff cause increased erosion through scouring in headwater areas and sediment deposition in downstream channels (Booth 1991, pp. 93, 102-105; Schram 1995, p. 88). Waterways are adversely affected in urban areas, where impervious cover rates are high, by sediment loads that are washed into streams or aquifers during storm events. Sediments are either deposited into layers or become suspended in the water column (Ford and Williams 1989, p. 537; Mahler and Lynch 1999, p. 177). Sediment derived from soil erosion has been cited as the greatest single source of pollution of surface waters by volume (Menzer and Nelson 1980, p. 632).

Excessive sediment from stormwater runoff is a threat to salamanders because it can cover habitat, cover substrates, and lead to declines in vegetative abundance and diversity (Geismar 2005, p. 2). Sediments suspended in water can clog gill structures, which impairs breathing of aquatic organisms, and can reduce their ability to avoid predators or locate food sources due to decreased visibility (Schueler 1987, p. 1.5). Excessive deposition of sediment in streams can physically reduce the

amount of available habitat and protective cover for aquatic organisms, by filling the interstitial spaces of gravel and rocks. As an example, a California study found that densities of two salamander species were significantly lower in streams that experienced a large infusion of sediment from road construction after a storm event (Welsh and Ollivier 1998, pp. 1,118-1,132). The vulnerability of the salamander species in this California study was attributed to their reliance on interstitial spaces in the streambed habitats (Welsh and Ollivier 1998, p. 1,128). We consider increased sedimentation from impervious cover to be a threat to all four central Texas salamanders, because it fills interstitial spaces, eliminates resting places, and reduces habitat of its prey base (small aquatic invertebrates) (O'Donnell

et al.

2006, p. 34).

Also, sediments eroded from contaminated soil surfaces can concentrate and transport contaminants (Mahler and Lynch 1999, p. 165). The four central Texas salamander species and their prey species are directly exposed to sediment-borne contaminants present within the aquifer and discharging through the spring outlets. For example, in addition to sediment, trace metals such as arsenic, cadmium, copper, lead, nickel, and zinc were found in Barton Springs in the early 1990s (COA 1997, pp. 229, 231-232). Contaminants may cause adverse effects to the salamander and its prey species including reduced growth and weight, abnormal behavior, morphological and developmental aberrations, and decreased reproductive activity (Albers 2003, p. 354).

Excess sedimentation may have contributed to declines in Jollyville Plateau salamander populations in the past. Monitoring by the City of Austin found that, as sediment deposition increased at several sites, salamander abundances significantly decreased (COA 2001, pp. 101, 126). Additionally, the City of Austin found that sediment deposition rates have increased significantly along one of the long-term monitoring sites (Bull Creek Tributary 5) as a result of construction activities upstream (O'Donnell

et al.

2006, p. 34). This site has had significant declines in salamander abundance, based on 10 years of monitoring, and the City of Austin attributes this decline to the increases in sedimentation (O'Donnell

et al.

2006, pp. 34-35). The location of this monitoring site is within a large preserved tract. However, the headwaters of this drainage are outside the preserve and the development in this area increased sedimentation downstream and impacted salamander habitat in the preserved tract.

Direct evidence of the effects of sedimentation on the Austin blind, Georgetown, and Salado salamanders is lacking, primarily due to limited studies on those species. However, analogies can be drawn from data on similar species, such as the Jollyville Plateau and Barton Springs salamanders. Barton Spring salamander population numbers are adversely affected by high turbidity and sedimentation (COA 1997, p. 13). Sediments discharge through Barton Springs, even during baseflow conditions (not related to a storm event) (Geismar 2005, p. 12). Storms can increase sedimentation rates substantially (Geismar 2005, p. 12). Areas in the immediate vicinity of the spring outflows lack sediment, but the remaining bedrock is sometimes covered with a layer of sediment several inches thick (Geismar 2005, p. 5). Sedimentation is a direct threat for the Austin blind salamander because its habitat in Barton Springs would fill with sediment if it were not for regular maintenance and removal (Geismar 2005, p. 12). Further development in the Barton Creek watershed will most likely be associated with diminished water clarity and a reduction in biodiversity of flora (COA 1997, p. 7). Likewise, development within the watersheds of Georgetown and Salado salamander sites will increase sedimentation and degrade water quality in salamander habitat. Therefore, because salamander population numbers are adversely affected by sedimentation covering habitat, filling in substrates, and transporting contaminants in both surface and subsurface habitats, we consider sedimentation and its resulting effects to be an ongoing, significant threat to all four central Texas salamanders' surface and subsurface habitats now and in the future. However, we consider the Salado salamander to salamander to be less affected by this threat than the other three species, due to the relatively low levels of impervious cover in its range.

Changes in Flow Regime Due to Impervious Cover

Impervious cover in a stream's watershed causes streamflow to shift from predominately baseflow, which is derived from natural filtration processes and discharges from local groundwater supplies, to predominately stormwater runoff. With increasing stormwater runoff, the amount of baseflow available to sustain water supplies during drought cycles is diminished and the frequency and severity of flooding increases. The increased quantity and velocity of runoff increases erosion and streambank destabilization, which in turn leads to increased sediment loadings, channel widening, and detrimental changes in the morphology and aquatic ecology of the affected stream system (Hammer 1972, pp. 1535-1536, 1540; Booth 1990, pp. 407-409, 412-414; Booth and Reinelt 1993, pp. 548-550; Schueler 1994, pp. 106-108; Pizzuto

et al.

2000, p. 82; Center for Watershed Protection 2003, pp. 41-48).

The changes in flow regime due to impervious cover can have a direct impact on salamander populations. For example, Barrett

et al.

(2010, pp. 2002-2003) recently observed that the density of aquatic southern two-lined salamanders declined more drastically in streams with urbanized watersheds compared to streams with forested or pastured watersheds. A statistical analysis indicated that this decline in urban streams was due to an increase in flooding frequency from stormwater runoff. Barrett et al. (2010, p. 2003) also used artificial stream experiments to demonstrate that salamanders were flushed downstream at significantly lower velocities when the substrate was sand-based, as compared to gravel, pebble, or cobble-based. Sand-based substrates are common to urban streams due to high sedimentation rates (see “Sedimentation from Stormwater Runoff” section, above). The combined effects of increased sand-based substrates due to high sedimentation rates, and increased flow velocities from impervious cover, result in effectively removing salamanders from their habitat.

Extreme flood events have occurred in all four salamander species' surface habitats (Pierce 2011a, p. 10; TPWD 2011a, p. 6; Turner 2009, p. 11; O'Donnell

et al.

2005, p. 15). It is reasonable to assume that impervious cover due to urbanization in the salamanders' watershed will continue to cause streamflow to shift from predominately baseflow to predominately stormwater runoff. For example, an examination of 24 stream sites in the Austin area revealed that increasing impervious cover in the watersheds resulted in decreased base flow, increased high-flow events of shorter duration, and more rapid rises and falls of the stream flow (Glick

et al.

2009, p. 9). In addition, increases in impervious cover within the Walnut Creek watershed (Jollyville Plateau salamander habitat) have probably caused a shift to more rapid rises and falls of the stream flow (Herrington 2010, p. 11). Because of the detrimental effects previously discussed in association with increased stormwater

runoff, and because the amount of baseflow available to sustain water supplies during drought cycles is diminished, we consider changes in flow regime due to impervious cover to be an ongoing threat to all four central Texas salamanders' surface habitats now and in the future. Because it only affects surface habitat, this threat is of moderate significance to the Austin blind, Jollyville Plateau, and Georgetown salamanders. We consider this threat to be of low significance for the Salado salamander due to the relatively low levels of impervious cover in its range.

Conclusion of Impervious Cover and Stormwater Runoff

In summary, impervious cover contributes to the degradation of surface and subsurface salamander habitat by transporting contaminants and sediments to the Edwards Aquifer. Impervious cover within the watersheds of the salamanders also leads to changes in streamflow regime that degrades surface salamander habitat. The Austin blind, Jollyville Plateau, and Georgetown salamanders all have levels of impervious cover in their ranges that may be causing declines in water quality. Impervious cover levels are relatively low in the range of the Salado salamander. However, growing human populations and the associated increase in urbanization indicate that impervious cover levels will continue to rise within the ranges of all four central Texas salamanders. Therefore, we consider impervious cover and stormwater runoff to be sources of stressors, such as contamination, sedimentation, and changes in streamwater's flow regime, that contribute to the overall risk of extinction for all four salamander species.

Land Application Contaminants

Excessive land application contaminants, such as nutrient and pesticide input to watershed drainages, are other forms of pollution that occur in highly urbanized areas. In comparison to nonkarstic aquifer systems, the Edwards Aquifer is more vulnerable to the effects of contamination due to: (1) A large number of conduits that offer no filtering capacity, (2) high groundwater flow velocities, and (3) the relatively short amount of time that water is inside the aquifer system (Ford and Williams 1989, pp. 518-519).

Even at low concentrations, land application contaminants, such as nutrients and pesticides, can disrupt aquatic life. Some of these chemicals may accumulate in the fatty tissue of aquatic organisms and impair their ability to reproduce, escape predation, maintain metabolic processes, and survive (Ross 2011, p. 6). In addition, macroinvertebrates, such as small freshwater crustaceans on which these four central Texas salamander species feed are especially sensitive to water pollution (Phipps

et al.

1995, p. 282; Miller

et al.

2007, p. 74).

Nutrients

Nutrient input (such as phosphorus and nitrogen) to watershed drainages, which often results in abnormally high organic growth in aquatic ecosystems, can originate from multiple sources, such as human and animal wastes, industrial pollutants, and fertilizers (from lawns, golf courses, or croplands) (Garner and Mahler 2007, p. 29). As the human population grows and subsequent urbanization occurs within the ranges of these four central Texas salamander species, they likely become more susceptible to the effects of excessive nutrients within their habitats. To illustrate, an estimated 102,262 domestic dogs and cats (pet waste is a potential source of excessive nutrients) were known to occur within the Barton Springs Segment of the Edwards Aquifer in 2010 (Herrington

et al.

2010, p. 15). Their distributions were correlated with human population density (Herrington

et al.

2010, p. 15).

Various residential properties and golf courses are known to use pesticides, herbicides, and fertilizers to maintain turfgrass within watersheds where Jollyville Plateau salamander populations are known to occur (COA 2003, pp. 1-7). Analysis of water quality constituents conducted by the City of Austin (1997, pp. 8-9) showed significant differences in nitrate, ammonia, total dissolved solids, total suspended solids, and turbidity concentrations between watersheds dominanted by golf courses, residential land, and rural land. Golf course tributaries were found to have higher concentrations of these constituents than residential tributaries, and both golf course and residential tributaries had substantially higher concentrations for these five constituents than rural tributaries (COA 1997, pp. 8-9).

Residential irrigation of wastewater effluent has led to excessive nutrient input into the recharge zone of the Barton Springs Segment of the Edwards Aquifer (Ross 2011, pp. 11-18). Wastewater effluent permits do not require treatment to remove metals, pharmaceutical chemicals, or the wide range of chemicals found in body care products, soaps, detergents, pesticides, or other cleaning products (Ross 2011, p. 6). These chemicals remaining in treated wastewater effluent can enter streams and the aquifer and alter water quality within salamander habitat.

Excessive nutrient input into aquatic systems can increase plant growth, which pulls more oxygen out of the water when the dead plant matter decomposes, resulting in less oxygen being available in the water for salamanders to breathe (Schueler 1987, pp. 1.5-1.6; Ross 2011, p. 7). A reduction in dissolved oxygen concentrations could not only affect respiration in salamander species, but also lead to decreased metabolic functioning and growth in juveniles (Woods

et al.

2010, p. 544), or death (Ross 2011, p. 6). Excessive plant material can also reduce stream velocities and increase sediment deposition (Ross 2011, p. 7). When the interstitial spaces become compacted or filled with fine sediment, the amount of available foraging habitat and protective cover is reduced (Welsh and Ollivier 1998, p. 1,128). Studies in the Bull Creek watershed found a loss of some sensitive macroinvertebrate species, potentially due to nutrient enrichment and sediment accumulation (COA 2001b, p. 15).

Poor water quality, particularly elevated nitrates, may also be a cause of morphological deformities in individual Jollyville Plateau salamanders. The City of Austin has documented very high levels of nitrates (averaging over 6 milligrams per liter (mg L

-1

) with some samples exceeding 10 mg L

-1

) and high conductivity at two monitoring sites in the Stillhouse Hollow drainage area (O'Donnell

et al.

2006, pp. 26, 37). For comparison, nitrate levels in undeveloped Edwards Aquifer springs (watersheds without high levels of urbanization) are typically close to 1 mg L

-1

(O'Donnell

et al.

2006, p. 26). The source of the nitrates in Stillhouse Hollow is thought to be lawn fertilizers (Turner 2005b, p. 11). Salamanders observed at the Stillhouse Hollow monitoring sites have shown high incidences of deformities, such as curved spines, missing eyes, missing limbs or digits, and eye injuries (O'Donnell

et al.

2006, p. 26). These deformities often result in the salamander's inability to feed, reproduce, or survive. The Stillhouse Hollow location was also cited as having the highest observation of dead salamanders (COA 2001, p. 88). Although no statistical correlations were found between the number of deformities and nitrate concentrations (O'Donnell

et al.

2006, p. 26), environmental toxins are the suspected cause of salamander deformities

(O'Donnell

et al.

2006, p. 25). Nitrate toxicity studies have indicated that salamanders and other amphibians are sensitive to these pollutants (Marco

et al.

1999, p. 2,837). Increased nitrate levels have been known to affect amphibians by altering feeding activity and causing disequilibrium and physical abnormalities (Marco

et al.

1999, p. 2,837).

In summary, as the human population grows and subsequent urbanization occurs within the ranges of these four central Texas salamander species, they likely will become more susceptible to the effects of excessive nutrients within their surface and subsurface habitats. Because of the detrimental effects associated with increased nutrient input, we consider nutrients to be an ongoing threat to all four central Texas salamanders' continued existence throughout their ranges.

Pesticides

Pesticides are also associated with urban areas. Sources of pesticides include lawns, road rights-of-way, and managed turf areas, such as golf courses, parks, and ball fields. Pesticide application is also common in residential, recreational, and agricultural areas. Pesticides have the potential to leach into groundwater through the soil or be washed into streams by stormwater runoff.

Some of the most widely used pesticides in the United States are atrazine, carbaryl, diazinon, and simazine (Mahler and Van Metre 2000, p. 1). These four pesticides were documented within the Austin blind salamander's habitat (Barton Springs Pool and Eliza Springs) in water samples taken at Barton Springs during and after a 2-day storm event (Mahler and Van Metre 2000, pp. 1, 6, 8). They were found at levels below criteria set in the aquatic life protection section of the Texas Surface Water Quality Standards (Mahler and Van Metre 2000, p. 4). In addition, elevated concentrations of organochlorine pesticides were found in Barton Springs sediments (Ingersoll

et al.

2001, p. 7). A later water quality study at Barton Springs from 2003 to 2005 detected atrazine, simazine, prometon, and deethylatrazine in low concentrations (Mahler

et al.

2006, p. 63). During storm events, additional contaminants were detected, including pharmaceutical compounds such as caffeine, acetaminophen, and cotinine (Mahler

et al.

2006, p. 64). The presence of these contaminants in Barton Springs indicates the vulnerability of salamander habitat to contaminant infiltration from surface land uses.

Another study by the U.S. Geological Survey detected insecticides (diazinon and malathion) and herbicides (atrazine, prometone, and simazine) in several Austin-area streams, most often at sites with urban and partly urban watersheds (Veenhuis and Slade 1990, pp. 45-47). Twenty-two of the 42 selected synthetic organic compounds analyzed in this study were detected more often and in larger concentrations at sites with more urban watersheds compared to undeveloped watersheds (Veenhuis and Slade 1990, p. 61). Other pesticides (dichlorodiphenyltrichloroethane, chlordane, hexachlorobenzene, and dieldrin) have been detected at multiple Jollyville Plateau salamander sites (COA 2001, p. 130).

The frequency and duration of exposure to harmful levels of pesticides have been largely unknown or undocumented for the four central Texas salamander species. Therefore, we do not know the extent to which pesticides and other waterborne contaminants have affected salamander survival, development, and reproduction, or their prey to date. However, pesticides are known to impact amphibian species in a number of ways. For example, Reylea (2009, p. 370) demonstrated that diazinon reduces growth and development in larval amphibians. Another pesticide, carbaryl, causes mortality and deformities in larval streamside salamanders (

Ambystoma barbouri

) (Rohr

et al.

2003, p. 2,391). The Environmental Protection Agency (EPA) (2007a, p. 9) also found that carbaryl is likely to adversely affect the Barton Springs salamander both directly and indirectly through reduction of prey. Additionally, atrazine has been shown to impair sexual development in male amphibians at concentrations as low as 0.1 part per billion (Hayes 2002, p. 5,477). Atrazine levels were found to be greater than 0.44 part per billion after rainfall in Barton Springs Pool (Mahler and Van Mere 2000, pp. 4, 12).

In summary, even though we do not know the extent to which pesticides have affected the surface and subsurface habitat of the four central Texas salamander species at this time, pesticides do pose a significant, ongoing threat to the continued existence of all four salamanders throughout their ranges.

Hazardous Material Spills

The Edwards Aquifer is at risk from a variety of sources of pollutants (Ross 2011, p. 4), including hazardous materials that have the potential to be spilled, resulting in contamination of both surface and groundwater resources (Service 2005, pp. 1.6-14-1.6-15). Any activity that involves the extraction, storage, manufacture, or transport of potentially hazardous substances, such as fuels or chemicals, can contaminate water resources and cause harm to aquatic life. Spill events can involve a short release with immediate impacts, such as a collision that involves a tanker truck carrying gasoline, or the release can be long-term, involving the slow release of chemicals over time such as a leaking underground storage tank. As of 1996, more than 6,000 leaking underground storage tanks in Texas have resulted in contaminated groundwater (Mace

et al.

1997, p. 2), including a large leak in the range of the Georgetown salamander (Mace

et al,

1997, p. 32). The risk of this type of contamination is expected to increase with increasing urbanization.

The transport of hazardous materials is common on many highways, which are major transportation routes (Service 2005, p. 1.6-13). Interstate Highway 35 crosses the watersheds that contribute groundwater to spring sites known to be occupied by all four salamander species. A catastrophic spill could occur if a transport truck overturned and its contents entered the recharge zone of the Northern Segment of the Edwards Aquifer. Transportation accidents involving hazardous materials spills at bridge crossings are of particular concern because recharge areas in creek beds can transport contaminants directly into the aquifer (Service 2005, p. 1.6-14). Salado salamander sites located downstream of Interstate Highway 35 may be particularly vulnerable due to their proximity to this major transportation corridor. Interstate Highway 35 crosses Salado Creek just 760 to 1,100 ft (231 to 335 m) from three spring sites (Big Boiling Springs, Lil' Bubbly Springs, and Lazy Days Fish Farm) where the Salado salamander is known to occur. Should a hazardous materials spill occur at the Interstate Highway 35 bridge that crosses at Salado Creek, the Salado salamander could be at risk from contaminants entering the water flowing into its surface habitat downstream.

In addition, the Texas Department of Transportation (TxDOT) is planning to reconstruct a section of Interstate Highway 35 within the Village of Salado (Najvar, 2009, Service, pers. comm., p. 1). This work will include replacing four bridges that cross Salado Creek (two main lane bridges and two frontage road bridges) in an effort to widen the highway at this location. This project could affect the risk of hazardous materials spills and runoff into Salado Creek upstream of known Salado

salamander locations. In August 2009, TxDOT began working with the Service to identify measures, such as the installation of permanent water quality control mechanisms to contain runoff, to protect the Salado salamander and its habitat from the effects of this project (Najvar 2009, pers. comm., p. 1).

Austin blind salamander habitat is similarly at risk from hazardous material spills that could contaminate groundwater. There is potential for a catastrophic gasoline spill in the Barton Springs Segment of the Edwards Aquifer, due to the presence of the Longhorn pipeline (Turner and O'Donnell 2004, pp. 2-3). Although a number of mitigation measures were employed to reduce the risk of a leak or spill from the Longhorn pipeline, such a spill could enter the aquifer and result in the contamination of salamander habitat at Barton Springs (EPA 2000, pp. 9-29-9-30).

Multiple water lines also run through the surrounding areas of Barton Springs. A water line break could potentially flow directly into Barton Springs, exposing salamanders to chlorine concentrations that are potentially toxic (Herrington and Turner 2009, pp. 5, 6). Sewage spills are the most common type of spill within the Barton Springs watershed and represent a potential catastrophic threat (Turner and O'Donnell 2004, p. 27). Sewage spills often include contaminants such as nutrients, PAHs, metals, pesticides, pharmaceuticals, and high levels of fecal coliform bacteria. Increased ammonia levels and reduced dissolved oxygen are the most likely impacts of a sewage spill that could cause rapid mortality of large numbers of salamanders (Turner and O'Donnell 2004, p. 27). Fecal coliform bacteria cause diseases in salamanders and their prey base (Turner and O'Donnell 2004, p. 27). Approximately 7,600 wastewater mains totaling 349 mi (561.6 km) are present in the Barton Springs Segment of the Edwards Aquifer (Herrington

et al.

2010, p. 16). In addition, there are 9,470 known septic facilities in the Barton Springs Segment as of 2010 (Herrington

et al.

2010, p. 5), up from 4,806 septic systems in 1995 (COA 1995, p. 3-13). In one City of Austin survey of these septic systems, over 7 percent were identified as failing (COA 1995, p. 3-18).

A contaminant spill could travel quickly through the aquifer to Barton Springs, where it could impact Austin blind salamander populations. Depending on water levels in the aquifer, groundwater flow rates through the Barton Springs Segment of the Edwards Aquifer can range from 0.6 mi (1 km) per day to over 4 mi (6 km) per day. The relatively rapid movement of groundwater under any flow conditions provides little time for mitigation efforts to reduce potential damage from a hazardous spill anywhere within the Barton Springs Segment of the Edwards Aquifer (Turner and O'Donnell 2004, pp. 11-13).

A number of point-sources of pollutants exist within the Jollyville Plateau salamander's range. Utility structures such as storage tanks or pipelines (particularly gas and sewer lines) can accidentally discharge. Leaking underground storage tanks have been documented as a problem within the Jollyville Plateau salamander's range (COA 2001, p. 16). Sewage spills from pipelines also have been documented in watersheds supporting Jollyville Plateau salamander populations (COA 2001, pp. 16, 21, 74). For example, in 2007, a sewage line overflowed an estimated 50,000 gallons (190,000 liters) of raw sewage into the Stillhouse Hollow drainage area of Bull Creek (COA 2007b, pp. 1-3). The location of the spill was a short distance downstream of currently known salamander locations, and no salamanders were thought to be affected.

The City of Austin also cites swimming pools as a potential threat to

Eurycea

salamanders if pools are drained into waterways or storm drains without dechlorination (COA 2001, p. 130). This is due to the concentrations of chlorine commonly used in residential swimming pools, which far exceed the lethal concentrations observed in experiments with the San Marcos salamander (

Eurycea nana

) (COA 2001, p. 130). Residential swimming pools can be found throughout the watersheds of several Jollyville Plateau salamander sites and may pose a risk to the salamanders if discharged into the storm drain system or waterways.

Data on chemical spills near the City of Georgetown are lacking, but the threat of groundwater contamination from accidental spills is still present. As recently as 2011, a fuel tanker overturned in Georgetown and spilled 3,500 gallons (13,249 liters) of gasoline (McHenry

et al.

2011, p. 1). A large plume of hydrocarbons was detected within the Edwards Aquifer underneath Georgetown in 1997 (Mace

et al,

1997, p. 32), probably the result of a leaking fuel storage tank. There are currently eight water treatment plants within the city limits, with wastewater and chlorinated drinking water lines running throughout Georgetown salamander stream drainages (City of Georgetown 2008, p. 3.37). A “massive” wastewater line is being constructed in the South San Gabriel River drainage (City of Georgetown 2008, p. 3.22), which is within the watershed of one known Georgetown salamander site. Almost 700 septic systems were permitted or inspected in Georgetown in 2006 (City of Georgetown 2008, p. 3.36). Even though data on chemical spills near the City of Georgetown are lacking, there is the potential for spills and contamination to occur from multiple sources.

Several groundwater contamination incidents have occurred within Salado salamander habitat (Price

et al.

1999, p. 10). Big Boiling Springs is located on the south bank of Salado Creek, near locations of past contamination events (Chippindale

et al.

2000, p. 43). Between 1989 and 1993, at least four incidents occurred within a quarter mile (0.4 km) from the spring site, including a 700-gallon (2,650-liter) and 400-gallon (1,514-liter) gasoline spill and petroleum leaks from two underground storage tanks (Price

et al.

1999, p. 10). Because no follow-up studies were conducted, we have no information to indicate what effect these spills had on the species or its habitat. However, between 1991 and 1998, only a single salamander was observed at Big Boiling Springs (TPWD 2011a, p. 2).

In summary, catastrophic hazardous material spills pose a potential significant threat to the Austin blind, Georgetown, and Salado salamanders due to their restricted ranges. A significant hazardous materials spill within a stream drainage for any of these species could have the potential to threaten the long-term survival and sustainability of multiple populations or possibly an entire species. The threats from spills increase substantially under drought conditions due to lower dilution and buffering capability of impacted waterbodies. Spills under low flow conditions are predicted to have an impact at much smaller volumes (Turner and O'Donnell 2004, p. 26). For example, it is predicted that at low flows (10 cubic feet per second [cfs]) a spill of 360 gallons (1,362.7 liters) of gasoline 3 miles (4.8 km) from Barton Springs could be catastrophic for the Austin blind salamander population (Turner and O'Donnell 2004, p. 26). Because the Austin blind salamander resides in only one spring system, a catastrophic spill in its surface and subsurface habitat could cause the extinction of this species in the wild. However, because the Jollyville Plateau salamander occurs in more populations over a broader range, the potential for a catastrophic hazardous materials spill to affect the overall species' status is small.

A hazardous materials spill has the potential to cause localized populations to go extinct, but we do not consider this to be a threat to the Jollyville Plateau salamander's overall continued existence. But, in combination with the other threats identified in this five-factor analysis, we think a catastrophic hazardous materials spill could contribute to the species' risk of extinction by reducing its long-term viability. We, therefore, consider hazardous material spills to be a potential significant threat for the Austin blind and Salado salamander due to their limited distributions. Hazardous material spills are less of a threat for the more widespread Georgetown salamander. These spills pose a low risk to the Jollyville Plateau salamander due to its more widespread distribution.

Construction Activities

Short-term increases in pollutants, particularly sediments, can occur during construction in areas of new development. When vegetation is removed and rain falls on unprotected soils, large discharges of suspended sediments can erode from newly exposed areas, resulting in increased sedimentation in downstream drainage channels (Schueler 1987, pp. 1-4; Turner 2003, p. 24; O'Donnell

et al.

2005, p. 15). This increased sedimentation from construction activities has been linked to declines in Jollyville Plateau salamander counts at multiple sites (Turner 2003, p. 24; O'Donnell

et al.

2006, p. 34). Cave sites are also impacted by construction, as Testudo Tube Cave (Jollyville Plateau salamander habitat) showed an increase in nickel, calcium, and nitrate/nitrite after nearby road construction (Richter 2009, pp. 6-7). Barton Springs (Austin blind salamander habitat) is also under the threat of pollutant loading due to its proximity to construction activities and location at the downstream side of the watershed (COA 1997, p. 237). The City of Austin (1995, p. 3-11) estimated that construction-related sediment and in-channel erosion accounted for approximately 80 percent of the average annual sediment load in the Barton Springs watershed. In addition, the City of Austin (1995, p. 3-10) estimated that total suspended sediment loads have increased 270 percent over pre-development loadings within the Barton Springs Segment of the Edwards Aquifer. At this time, we are not aware of any studies that have examined sediment loading due to construction activities within the watersheds of Georgetown or Salado salamander habitats. However, because construction occurs in many of these watersheds, we believe that the threat of construction in areas of new development applies to these species as well. Construction is intermittent and temporary, but it affects both surface and subsurface habitats. Therefore, we have determined that this threat is ongoing and is and will continue to affect the Austin blind, Jollyville Plateau, and Georgetown salamanders and their habitats. However, we consider this threat to affect the Salado salamander to a lesser degree due to the relatively low levels of impervious cover in its range.

Also, the physical construction of pipelines has the potential to modify subsurface habitat for salamander species. It is known that these salamanders inhabit the subsurface environment. Tunneling for underground pipelines can destroy potential habitat by removing subsurface material. Additional material can become dislodged and result in increased sediment loading into the aquifer and associated spring systems. In addition, disruption of water flow to springs inhabited by salamanders can occur through the construction of tunnels and vertical shafts. Because detailed maps of the underground conduits that feed springs in the Edwards Aquifer are not available, tunnels and shafts have the possibility of intercepting and severing those conduits (COA 2010b, p. 28). Affected springs could rapidly become dry and would not support salamander populations. The closer a shaft or tunnel location is to a spring, the more likely that the construction will impact a spring (COA 2010b, p. 28). This has presumably occurred in the past at Moss Gulley Spring, where the drilling of a nearby test well in the mid-1980s led to the dewatering of the spring (Hillis

et al.

2010, p. 2). Jollyville Plateau salamanders have not been observed at that site since the spring stopped flowing (Hillis

et al.

2010, p. 2). Even small shafts pose a threat to nearby spring systems, and therefore, we consider construction of pipelines to be a future threat to the surface and subsurface habitat of all four salamander species. However, we consider this a low significance threat for the Jollyville Plateau salamander because tunnels or shafts are likely to only impact a few populations. Because there are currently no known projects that are likely to occur within the species' range, we consider this a threat of low significance for the Austin blind, Georgetown, and Salado salamanders.

Likewise, we consider tunnel and shaft construction to be a threat to the Jollyville Plateau salamander's surface and subsurface habitat due to its potential to intercept groundwater flow and dewatering. In 2011, construction began on the Jollyville Transmission Main (JTM), a tunnel designed to transport treated drinking water from Water Treatment Plant No. 4 to the Jollyville Reservoir. The project also includes four working shafts along the tunnel route (COA 2010b, p. 1). Because the tunnel is being constructed below the Edwards Aquifer and below the permeable portion of the Glen Rose formation (COA 2010b, p. 42; Toohey 2011, p. 1; COA 2011c, p. 36, 46), the threat to the salamander from this particular tunnel is considered low. The vertical shafts that are being drilled down through the Edwards Aquifer are a more significant concern.

Of the four shafts, only the one at the Four Points location appears to be a potential threat to any Jollyville Plateau salamanders. The Parks and Recreation Department (PARD) shaft is in the Glen Rose (not the Edwards) formation (Service 2010a; COA 2011c, p. 33) and therefore is not expected to affect Edwards Aquifer groundwater. The Jollyville Reservoir Shaft is on the other side of a groundwater divide from any springs within a mile of the site (Service 2010a). The shaft at the water treatment plant is going through a portion of the Edwards formation that is dry (COA 2011c, p. 33). There are 8 of 92 known Jollyville Plateau salamander sites within 1 mi (1.6 km) of the Four Points shaft location. The closest locations (Spring 21 and Spring 24) are about 2,000 ft (610 m) or greater from the shaft. Best management practices designed to protect groundwater resources have been implemented into the design and construction of the JTM shafts. These practices include, but are not limited to: Monitoring groundwater quality and spring flow, minimizing sediment discharges during construction, developing a groundwater impact contingency plan, locating working shafts in areas where the chance of encountering conduits to salamander springs is reduced, and re-routing conduit flow paths around the shaft if encountered (COA 2010b, pp. 51-55).

We believe that these best management practices have lowered the magnitude of the threat to the Jollyville Plateau salamander. However, a leak occurred at one shaft site (Four Points) in December 2011, and it was associated with an initial 1-foot (0.3 m) drop in the aquifer level (Toohey 2011, p. 2) as measured in a monitoring well 10 ft (3 m) away. A 1-foot (0.3-m) drop in water level was also seen in a monitoring well 100 ft (30 m) away, but not in

monitoring wells farther out. The City did not see any drops in flow at the springs they were monitoring or in wells between those springs and the well 100 ft away; however, they do not have access to the closest springs (mentioned above). Since that time, grout has been injected into the shaft wall to stop the leak. Preliminary evidence indicates that the grout injection resulted in a tight seal at the site of the leak (Lesniak 2012, City of Austin, pers. comm.). Even so, we consider tunnel and shaft construction of the JTM to be a threat now to the Jollyville Plateau salamander's habitat due to its potential to intercept groundwater flow and to dewater; however, we consider this threat to be of low significance because the best management practices have been implemented into the design and construction of the JTM shafts to protect groundwater resources.

Lastly, limestone rock is an important raw material that is mined in quarries all over the world due to its popularity as a building material and its use in the manufacture of cement (Vermeulen and Whitten 1999, p. 1). The construction activities within rock quarries can permanently alter the geology and groundwater hydrology of the immediate area, and adversely affect springs that are hydrologically connected to impacted sites. The potential environmental impacts of quarries include outright destruction of springs or collapse of karst caverns, as well as impacts to water quality through siltation and sedimentation, and impacts to water quantity through water diversion, dewatering, and reduced flows (Ekmekci 1990, p. 4). Limestone is a common geologic feature of the Edwards Aquifer, and active quarries exist throughout the region. For example, at least three Georgetown salamander sites (Avant Spring, Knight (Crockett Gardens) Spring, and Cedar Breaks Hiking Trail Spring) occur adjacent to a limestone quarry that has been active since at least 1995. The population status of the Georgetown salamander is unknown at Knight Spring and Cedar Breaks Hiking Trail Spring, but salamanders are seen infrequently and in low abundance at the closest spring to the quarry (Avant Spring; Pierce 2011c, pers. comm.). Because quarries may only affect a small portion of the species' ranges, we consider the mining of limestock rock to be an ongoing threat with limited effect to the Georgetown, Jollyville Plateau, and Salado salamanders, but not the Austin blind salamander. The Austin blind salamander's range is located in downtown Austin, and there are no active limestone quarries within the species' range.

Water Quantity Reduction in Relation to Urbanization

The Northern Segment of the Edwards Aquifer is the primary supply of water for Jollyville Plateau, Georgetown, and Salado salamander habitat (Cole 1995, p. 33; TPWD 2011a, p. 3). In general, the aquifer has been described as localized, small, and highly susceptible to drying or draining (Chippindale

et al.

2000, p. 36).

Urbanization and rapid population growth in the Northern Segment of the Edwards Aquifer may contribute to reduced spring flows due to increases in groundwater pumping. From 1980 to 2000, groundwater pumping in the Northern Segment of the Edwards Aquifer nearly doubled (TWDB 2003, pp. 32-33). The City of Georgetown predicts the average water demand to increase from 8.21 million gallons per day in 2003, to 10.9 million gallons per day by 2030 (City of Georgetown 2008, p. 3.36). Under peak flow demands (18 million gallons per day in 2003), the City of Georgetown uses seven groundwater wells in the Edwards Aquifer (City of Georgetown 2008, p. 3.36). Total water use for Williamson County was 73,532 ac ft in 2010, and is projected to increase to 98,268 ac ft by 2020, and to 211,854 ac ft by 2060, representing a 188 percent increase over the 50-year period (TWDB 2010, p. 46). Similarly, Bell County and Travis County expect a 59 percent and 91 percent increase in total water use over the same 50-year period, respectively (TWDB 2010, pp. 46, 64).

One prediction of future groundwater use in this area suggests a large drop in pumping as municipalities convert from groundwater to surface water supplies (TWDB 2003, p. 65). However, it is unknown if this reduction in groundwater use translates to adequate spring flows for salamanders. Increased urbanization in the watershed has been cited as one factor, in combination with drought, causing declines in spring flows (City of Austin 2006, pp. 46-47; TPWD 2011a, pp. 4-5). Urbanization removes the ability of the watershed to allow slow filtration of water through soils following rain events. Instead rainfall runs off impervious surfaces and into stream channels at higher rates, increasing downstream flows and decreasing groundwater recharge (Miller

et al.

2007, p. 74).

The City of Austin found a negative correlation between urbanization and spring flows at Jollyville Plateau salamander sites (Turner 2003, p. 11). Field studies have also shown that a number of springs that support Jollyville Plateau salamanders have already gone dry periodically, and that spring waters resurface following rain events (O'Donnell

et al.

2006, pp. 46-47). The San Gabriel Springs (Georgetown salamander habitat) are now intermittently flowing in the summer due to pumping from nearby water wells (TPWD 2011a, p. 9). Salamanders have not been seen on the surface there since 1991 (Chippindale

et al.

2000, p. 40; Pierce 2011b, pers. comm.).

In combination with drought, groundwater pumping has a direct impact on spring flows. Groundwater availability models demonstrate that 1 cfs of pumping will diminish Barton Springs spring flow by 1 cfs under drought-of-record (1950s drought) conditions (Smith and Hunt 2004, pp. 24, 36). Under the same conditions, these models suggest that present-day pumping rates will temporarily cease Barton Springs flow on a daily basis (Smith and Hunt 2004, pp. 24, 36).

Groundwater pumping can lead to saline water encroachments in the aquifer. As groundwater levels decline, a decrease in hydrostatic pressure occurs and saline groundwater is able to penetrate up into the lower portion of the aquifer (Pavlicek

et al.

1987, p. 2). This saline water encroachment would threaten the freshwater biota in the springs and the aquifer, including the four central Texas salamander species and their prey, by dramatically increasing the water salinity. Water quality in the Barton Springs Segment of the Edwards Aquifer has been degraded in the past due to saline encroachment (Slade

et al.

1986, p. 62). This water quality degradation occurred when Barton Springs discharge was less than 30 cfs (Slade

et al.

1986, p. 64). An analysis of more recent data found similar declines in water quality as the flow of Barton Springs dropped into the 20 to 30 cfs range (Johns 2006, pp. 6-7). As mentioned earlier, reduced groundwater levels would also increase the concentration of pollutants in the aquifer. Flows at Barton Springs dropped below 17 cfs as recently as mid-November 2011 (Barton Springs/Edwards Aquifer Conservation District 2011, p. 1).

Although water quantity decreases and spring flow declines are cited as a threat to

Eurycea

salamanders (Corn

et al.

2003, p. 36; Bowles

et al.

2006, p. 111), these species display some adaptive behavior to deal with periods of periodic surface flow losses. All four salamander species apparently spend some part of their life history in underground aquatic habitats and have the ability to retreat underground when

surface flows decline. For example, one of the City of Austin monitoring sites where Jollyville Plateau salamanders are most abundant undergoes periods where there is no surface water habitat available for the salamander (O'Donnell

et al.

2006, p. 47). Jollyville Plateau salamander juveniles were observed at Lanier Spring following 10 months of dry conditions on the surface, indicating that the salamanders are likely able to reproduce in the subsurface environment during a drought (Bendik 2011a, p. 32). Salado salamanders also reappeared in Robertson Springs after the springs went temporarily dry in 2009 (TPWD 2011a, p. 5). However, drying spring habitats can result in stranding salamanders, resulting in death of individuals (O'Donnell

et al.

2006, p. 16). It is also known that prey availability for carnivores is low underground due to the lack of primary production (Hobbs and Culver 2009, p. 392). This is supported by recent evidence of “shrinkage” in Jollyville Plateau salamander body length following periods of no springflow (Bendik 2011b, pers. comm.). Length measurements taken during a COA mark-recapture study at Lanier Spring demonstrated that Jollyville Plateau salamanders had negative growth during a 10-month period of no springflow in 2008-2009 (Bendik 2011b, pers. comm.). Therefore, although central Texas salamanders can survive and reproduce underground, the best available scientific evidence shows that these animals need the energy-rich surface habitat for positive growth and development.

In summary, water quantity reduction in relation to urbanization is an ongoing threat to all four salamanders throughout their ranges, primarily due to increased groundwater pumping in the presence of drought conditions and potential increases in saline water encroachments in the aquifer. However, we believe this threat is having or likely to have only a moderate effect, because the salamanders have the ability to retreat underground when surface flows decline.

Physical Modification of Surface Habitat

All four salamanders are sensitive to direct physical modification of surface habitat from impoundments, feral hogs, livestock, and other human activities. Because these threats only impact the surface habitat of salamanders, and because each species has the ability to retreat to subsurface habitats for shelter, none of these threats is likely to result in a significant impact to the species or their habitat. However, in combination with other threats discussed above, these threats may contribute to the species' risk of extinction.

Impoundments

Impoundments disrupt the natural flow regime of streams, leading to a variety of stressors that impact the salamanders and their surface habitats. For example, a low water crossing on a tributary of Bull Creek, occupied by the Jollyville Plateau salamander, resulted in sediment build-up below the impoundment and a scour hole above the impoundment that supported predaceous fish (O'Donnell

et al.

2008, p. 1). As a result, Jollyville Plateau salamanders were not found in this degraded habitat after the impoundment was constructed. When the crossing was removed in October 2008, the sediment build-up was removed, the scour hole was filled, and salamanders were later observed (Bendik 2011b, pers. comm.). Many low-water crossings are present near other Jollyville Plateau salamander sites (Bendik 2011b, pers. comm.). Impoundments only impact the surface habitat of salamanders. Because impoundments are likely to impact a small portion of the species' range, we consider impoundments caused by low-water crossings to be an ongoing threat of limited effect on the Jollyville Plateau salamander and its surface habitat, now and in the future.

Impoundments have also impacted surface habitat for the other salamander species. Most of the spring outlets in the Village of Salado, including the Salado salamander type locality at Big Boiling Springs, were modified by dam construction in the mid-1800s, to supply power to various mills (Brune 1981, p. 67). Two sites for the Georgetown salamander have spring openings that are confined to brick and mortar spring boxes (White 2011, SWCA, pers. comm.; Booker 2011, p. 1), presumably to collect the spring water for cattle. All spring sites for the Austin blind salamander (Main, Eliza, and Sunken Garden springs) have been impounded for recreational use. These sites were impounded in the early to mid-1900s. For example, Eliza Spring now discharges from 7 openings (each 1 ft (0.3 m) in diameter) in the concrete floor and 13 rectangular vents along the edges of the concrete. While the manmade structures help retain water in the spring pools during low flows, they have altered the salamander's natural environment. The impoundments have changed the Barton Springs ecosystem from a stream-like system to a more lentic (still water) environment, thereby reducing the water system's ability to flush sediments downstream and out of salamander habitat. Although a natural surface flow connection between Sunken Gardens Spring and Barton Creek has been restored recently (COA 2007c, p. 6), the Barton Springs system as a whole remains highly modified. Therefore, we consider impoundments to be an ongoing threat to the Salado, Georgetown, and Austin blind salamanders and their surface habitat, now and in the future. This threat has a limited effect on the Salado and Georgetown salamanders because it impacts a small portion of the species' ranges, but has a large effect on the Austin blind salamander because it affects this species' entire range.

Feral Hogs

There are between 1.8 and 3.4 million feral hogs (

Sus scrofa

) in Texas (TAMU 2011, p. 2). They prefer to live around moist areas, including riparian areas near streams, where they can dig into the soft ground for food and wallow in mud to keep cool (Mapson 2004, pp. 11, 14-15). Feral hogs disrupt these ecosystems by decreasing plant species diversity, increasing invasive species abundance, increasing soil nitrogen, and exposing bare ground (Texas A&M University (TAMU) 2012, p. 4). Feral hogs negatively impact surface salamander habitat by digging and wallowing in spring heads, which increases sedimentation downstream (O'Donnell

et al.

2006, pp. 34, 46). They have been cited as a source of elevated bacteria, nitrates, and phosphorus to streams in the Austin area (Timmons

et al.

2011, pp. 1-2).

Feral hogs have become abundant in some areas where the Jollyville Plateau, Georgetown, and Salado salamanders occur. O'Donnell

et al.

(2006, p. 34) noted that feral hog activity was increasing in the Bull and Cypress creek watersheds. Evidence of hogs has also been observed near one Georgetown salamander site (Cobbs Spring) (Booker 2011, p. 1). The landowner of Cobbs Spring is actively trapping feral hogs (Booker 2011, p. 1), but the effectiveness of this management has not been assessed. Feral hogs are also present in the area of several Salado salamander sites. Fortunately, feral hogs cannot access Austin blind salamander sites due to fencing and their location in downtown Austin.

In summary, because of their abundance and potential to negatively impact surface salamander habitat, we consider feral hogs to be an ongoing threat of low significance to the Jollyville Plateau, Georgetown, and Salado salamanders. As previously stated, we do not consider feral hogs to

be a threat to the Austin blind salamander at this time.

Livestock

Similar to feral hogs, livestock can negatively impact surface salamander habitat by disturbing the substrate and increasing sedimentation in the spring run where salamanders are often found. Poorly managed livestock grazing results in changes in vegetation (from grass-dominated to brush-dominated), which leads to increased erosion of the soil profile (COA 1995, p. 3-59). Grazing near streams can negatively impact nutrients, bacteria, species diversity, and water temperature in stream systems (COA 1995, p. 3-62). Evidence of trampling and grazing in riparian areas from cattle can be found at one Georgetown salamander site (White 2011, SWCA, pers. comm.), and cattle are present on at least one other Georgetown salamander site. Cattle are also present on lands where four Salado salamander sites occur (Gluesenkamp 2011b, pers. comm.; Texas Section Society for Range Management 2011, p. 2). Austin blind salamander habitat is inside a City of Austin park, and livestock are not allowed in the spring areas. Much of the Jollyville Plateau salamander habitat is in suburban areas, and we are not aware of livestock damage in those areas.

There is some management of livestock occurring that reduces the magnitude of negative impacts. An 8,126-ac (3,288-ha) property in Bell County with at least three Salado salamander sites has limited its cattle rotation to a maximum of 450 head (Texas Section Society for Range Management 2011, p. 2), which is considered a moderate stocking rate. The landowners at four of the springs with Salado salamanders have been considering options for fencing off spring outlets to protect the salamander habitat from cattle damage (Harrell 2012, Service, pers. comm.). In addition, the landowner of Cobbs Spring (a Georgetown salamander site) is in the process of phasing out cattle on the property (Boyd 2011, Williamson County Conservation Foundation, pers. comm.).

In summary, even though livestock may be having impacts at four of the seven Salado salamander spring sites, we believe livestock to be an ongoing threat of low impact to this salamander's habitat because there is some management of the livestock that reduces the magnitude of negative impacts. Even though habitat degradation by livestock is a factor that seems to be impacting the habitat of the Georgetown salamander, we do not believe it is occurring at a scale that significantly contributes to the risk of extinction of the species on its own. However, in combination with the other threats identified in this five-factor analysis, we think livestock may be contributing to the species' risk of extinction by reducing its long-term viability. Livestock are not a threat to the continued existence of the Austin blind or Jollyville Plateau salamanders.

Other Human Activities

Some sites for the four central Texas salamanders have been directly modified by human-related activities. In the summer of 2008, a spring opening at a Salado salamander site was covered with gravel (Service 2010b, p. 6). Although we received anecdotal information that at least one salamander was observed at the site after the gravel was dumped at Big Boiling Springs, the Service has no detailed information on how the Salado salamander was affected by this action. Heavy machinery is continuously used in the riparian area of Big Boiling and Lil' Bubbly Springs to clear out vegetation and maintain a grassy lawn to the water's edge (Gluesenkamp 2011a,b, pers. comm.), which has led to erosion problems during flood events (TPWD 2011a, p. 6). The modification of springs for recreation or other purposes degrades natural riparian areas, which are important for controlling erosion and attenuating floodwaters in aquatic habitats. Other continuing human activities at Big Boiling Spring include pumping water from the spring opening, contouring the substrate of the spring environment, and covering spring openings with gravel (TPWD 2011a, p. 4). For example, in the fall of 2011, the outflow channels and edges of these two springs were reconstructed with large limestone blocks and mortar. In addition, in response to other activity in the area, the U.S. Army Corps of Engineers issued a cease and desist order to the Salado Chamber of Commerce in October 2011, for unauthorized discharge of dredged or fill material that occurred in this area (Brooks 2011, U.S. Corps of Engineers, pers. comm.). This order was issued in relation to the need for a section 404 permit under the Clean Water Act (33 U.S.C. 1251 et seq.). Also in October 2011, a TPWD game warden issued a citation to the Salado Chamber of Commerce due to the need for a sand and gravel permit from the TPWD for work being conducted within TPWD's jurisdiction (Heger 2012a, TPWD, pers. comm.). The citation was issued because the Salado Chamber of Commerce had been directed by the game warden to stop work within TPWD's jurisdiction, which Salado Chamber of Commerce did temporarily, but work started again in spite of the game warden's directive (Heger 2012a, pers. comm.). A sand and gravel permit was obtained on March 21, 2012. The spring run modifications were already completed by this date, but further modifications in the springs were prohibited by the permit. Additional work on the bank upstream of the springs was permitted and completed (Heger 2012b, pers. comm.).

Because the Salado salamander is only known from seven spring locations, any type of human-related activities, such as pumping water from a spring opening, contouring the substrate of a spring environment, and covering spring openings with gravel, may have significant detrimental effects on the salamander and its habitat. These activities only affect the surface salamander habitat. Therefore, we consider these types of human-related activities to be ongoing threats of low impact to the Salado salamander's continued existence.

Furthermore, frequent human visitation associated with easily accessed habitat of the four salamanders may negatively affect the species and their habitat. Documentation from the City of Austin of disturbed vegetation, vandalism, and the destruction of travertine deposits (fragile rock formations formed by deposit of calcium carbonate on stream bottoms) by foot traffic has been documented at one of their Jollyville Plateau salamander monitoring sites in the Bull Creek watershed (COA 2001, p. 21) and may result in direct destruction of small amounts of the salamander's habitat. Eliza Spring and Sunken Garden Spring, two of the three locations of the Austin blind salamander, also experience vandalism, despite the presence of fencing and signage (Dries 2011, City of Austin, pers. comm.). The deep water of the third location (Main Pool) likely protects the Austin blind salamander's surface habitat from damage from frequent human recreation. Therefore, we consider human visitation to be an ongoing threat of low impact to the Jollyville Plateau salamander, and a threat of moderate impact to the Austin blind salamander, now and in the future.

Lastly, at the complex of springs occupied by the Georgetown salamander within San Gabriel River Park, a thick bed of nonnative granite gravel has been placed in the spring runs (TPWD 2011a, p. 9). This pea gravel is too small to serve as cover habitat and does not form the interstitial spaces required for

Georgetown salamanders. Salamanders have not been observed here since 1991 (Chippindale

et al.

2000, p. 40; Pierce 2011b, pers. comm.). Gravel dumping has not been documented at any other Georgetown salamander sites. Because this activity may have contributed to the decline of only this single population, we do not consider substrate modification in the form of gravel dumping to be a threat to the existence of the Georgetown salamander by itself. However, in combination with the other threats identified in this five-factor analysis, we think substrate modification may be contributing to the species' risk of extinction by reducing its long-term viability.

Drought and Flooding

Broad drought and flooding events have proven to have large impacts on the central Texas salamanders by drastically reducing or increasing the amount of water and affecting habitat quality.

Drought

The presence of water is an essential component to salamander habitat. Drought conditions alter the hydrologic conditions resulting in lowering groundwater tables and reduced spring flows. The impacts of drought are compounded by other consumptive uses of the aquifer such as groundwater pumping. The Northern Segment of the Edwards Aquifer, which supplies water to Jollyville Plateau, Georgetown, and Salado salamander habitat, is vulnerable to drought (Chippindale

et al.

2000, p. 36). In particular, the portion of the Edwards Aquifer underlying the Jollyville Plateau is relatively shallow, with a high elevation, thus being unlikely to be able to sustain spring flows during periods of drought (Cole 1995, pp. 26-27). Drought in the watershed has been cited as one factor, in combination with urbanization, causing declines in spring flows (O'Donnell

et al.

2006, pp. 46-47). A recent drought lasting from 2008 to 2009 was considered one of the worst droughts in central Texas history and caused numerous Jollyville Plateau salamander sites to go dry (Bendik 2011a, p. 31). An even more pronounced drought throughout Texas began in 2010, with the period from October 2010, through September 2011, being the driest 12-month period in Texas since rainfall records began (LCRA 2011, p. 1). Rainfall in early 2012 has lessened the intensity of the current drought, but below average rainfall and above average temperatures are forecasted for the summer of 2012 (LCRA 2012, p. 1).

Low flow conditions during drought also have negative impacts to the Austin blind salamander and its ecosystem in the Edwards Aquifer and at Barton Springs. The long-term average flow at the Barton Springs outlets is approximately 53 cfs (City of Austin 1998, p. 13; Smith and Hunt 2004, p. 10). The lowest flow recorded at Barton Springs was about 10 cfs during a record drought in the 1950s (COA 1998, p. 13). Discharge at Barton Springs decreases as water levels in the Barton Springs Segment of the Edwards Aquifer drop. Decreased discharge is associated with increases in water temperature, decreases in spring flow speed, and increases in sedimentation (COA 2011d, pp. 19, 24, 27). Large declines in aquifer levels have historically been due to a lack of adequate rainfall recharging the aquifer. In a 2004 groundwater flow modeling study, the Barton Springs Edwards Aquifer Conservation District predicted that under drought-of-record conditions and current pumping levels, the mean monthly springflow would be about 1 cfs. This study also indicated that under drought-of-record conditions, projected pumping rates for future years would cause Barton Springs to cease flowing for at least 4 months out of a year (Smith and Hunt 2004, pp. 1, 20, 24).

The specific effects of low flow on central Texas salamanders can be inferred by examining studies on the Barton Springs salamander. Drought decreases spring flow and dissolved oxygen levels and increases temperature in Barton Springs (Turner 2004, p. 2; Turner 2009, p. 14). Low dissolved oxygen levels decrease reproduction in Barton Springs salamanders (Turner 2004, p. 6; 2009, p. 14). Turner (2009, p. 14) also found that Barton Springs salamander counts decline with decreasing discharge (and thus declining dissolved oxygen levels). A prolonged drought from June 2008 through September 2009 caused decreases in Barton Springs salamander abundance (COA 2011d, pp. 19, 24, 27). The drought in 2011 resulted in dissolved oxygen concentrations so low that City of Austin used an aeration system to maintain oxygenated water in Eliza and Sunken Gardens Springs (Dries 2011, City of Austin, pers. comm.). Drought also lowers water quality in Barton Springs due to saline water encroachments in the Barton Springs Segment of the Edwards Aquifer (Slade

et al.

1986, p. 62; Johns 2006, p. 8).

In summary, we consider drought to be an ongoing threat to all four salamanders, because it can cause direct mortality to salamanders by desiccation if they are unable to retreat underground, it increases competition for spaces and resources (Bendik 2011a, p. 31), and it negatively affects their habitat, as discussed above. However, we consider the threat of drought to have a limited impact to all four central Texas salamanders and their habitats because they may be evolutionarily adapted to drought conditions that are common to the region (Bendik 2011a, pp. 31-32). At the same time, climate change and groundwater pumping may exacerbate drought conditions to the point where salamanders cannot adapt (see “Climate Change”, below, and “Water Quantity Reduction in Relation to Urbanization”, above).

Flooding

Flooding as a result of rainfall events can dramatically alter the substrate and hydrology of salamander habitat. A flood event in September 2010 modified surface habitat for the Georgetown salamander at two sites (Pierce 2011a, p. 10). The stormwater runoff caused erosion, scouring of the streambed channel, the loss of large rocks, and the creation of several deep pools. Salamander densities dropped dramatically in the days following the flood, and at one site, remained at low levels until habitat restoration (returning large rocks to the spring run) took place in the spring of 2011 (Pierce 2011a, p. 11). Likewise, three storm events in 2009 and 2010 deposited sediment and other material on top of spring openings at Salado Spring, preventing salamanders from foraging (TPWD 2011a, p. 6). The increased flow rate from flooding causes unusually high dissolved oxygen concentrations, which may exert direct or indirect, sub-lethal effects (reduced reproduction or foraging success) on salamanders (Turner 2009, p. 11). In addition, Geismar (2005, p. 2) found that flooding increases contaminants and sediments in Barton Springs. In 2007, flooding resulted in repeated accumulation of sediment in the Main Pool of Barton Springs that was so rapid that cleaning by City of Austin staff was not frequent enough to keep the surface habitat from becoming embedded (COA 2007c, p. 4). Flooding likely has similar effects on contaminants and sediments in other salamander habitat, but we are not aware of other studies.

The four salamanders' surface habitat is characterized by shallow water depth (COA 2001, p. 128; Pierce 2011a, p. 3), but deep pools are sometimes formed within stream channels from the scouring of floods. Tumlison

et al.

(1990, p. 172) found that the abundance of one

Eurycea

species decreased as

water depth increased. This relationship may be caused by an increase in predation pressure, as deeper water supports predaceous fish populations. However, several central Texas

Eurycea

species are able to thrive in deep water environments in the presence of many predators (for example, San Marcos salamander in Spring Lake,

Eurycea

sp. in Landa Lake, Barton Springs salamander in Barton Springs Pool). Anti-predator behaviors may allow these species to co-exist with predaceous fish, and the effectiveness of these behaviors may be species-specific (reviewed in Pierce and Wall 2011, pp. 18-19). The specific resistance to predation from fish for the four central Texas salamanders is unknown. In any case, flooding can alter the surface habitat by deepening stream channels, which may increase predaceous fish.

Also, salamanders may be flushed from the surface habitat by strong flows during flooding. Bowles

et al.

(2006, p. 117) observed no Jollyville Plateau salamanders in riffle habitat at one site during high water velocities and hypothesized that individual salamanders were either flushed downstream or retreated to the subsurface. This site had a relatively undeveloped watershed (Bowles

et al.

2006, p. 112), indicating that the runoff was largely natural and not caused by impervious cover.

In conclusion, flooding is a naturally occurring event that all four salamander species have adapted to in the past. Further, even though flooding is a factor that seems to be impacting all four salamanders' surface habitats, we do not believe it is occurring at a scale that would cause the extinction of any of the salamanders on its own. Because of this, we consider flooding on its own to have a limited effect on the species and their habitats. However, in combination with the other threats identified in this five-factor analysis, we think flooding may be contributing to the species' risk of extinction by reducing its long-term viability. The intensity of flooding events has increased due to increases in impervious cover. As previously noted, once natural vegetation in a watershed is replaced with impervious cover, rainfall is converted to surface runoff instead of filtering through the ground (Schueler 1991, p. 114). Impervious cover in a stream's watershed causes streamflow to shift from predominately baseflow, which is derived from natural filtration processes and discharges from local groundwater supplies, to predominately stormwater runoff. With increasing stormwater runoff, the amount of baseflow available to sustain water supplies during drought cycles is diminished and the frequency and severity of flooding increases. Because of the detrimental effects previously discussed in association with increased stormwater runoff, we consider changes in flow regime due to impervious cover to be an ongoing threat to all four central Texas salamanders' surface habitats.

Climate Change

Future climate change could potentially affect water quantity and spring flow for the four salamander species. According to the Intergovernmental Panel on Climate Change (IPCC 2007, p. 1), “warming of the climate system is unequivocal, as is now evident from observations of increases in global averages of air and ocean temperatures, widespread melting of snow and ice, and rising global average sea level.” Localized projections suggest the southwest United States may experience the greatest temperature increase of any area in the lower 48 States (IPCC 2007, p. 8), with warming increases in southwestern States greatest in the summer. The IPCC also predicts hot extremes, heat waves, and heavy precipitation will increase in frequency (IPCC 2007, p. 8).

Climate change could compound the threat of decreased water quantity at salamander spring sites. An increased risk of drought could occur if evaporation exceeds precipitation levels in a particular region due to increased greenhouse gases in the atmosphere (CH2M HILL 2007, p. 18). The Edwards Aquifer is also predicted to experience additional stress from climate change that could lead to decreased recharge and low or ceased springflows given increasing pumping demands (Loáiciga

et al.

2000, pp. 192-193). CH2M HILL (2007, pp. 22-23) identified possible effects of climate change on water resources within the Lower Colorado River Watershed (which contributes recharge to Barton Springs). A reduction of recharge to aquifers and a greater likelihood for more extreme droughts were identified as potential impacts to water resources (CH2M HILL 2007, p. 23). The droughts of 2008 to 2009, and 2010 to 2011, were two of the worst in central Texas history, with the period from October 2010, through September 2011, being the driest 12-month period in Texas since rainfall records began (LCRA 2011, p. 1). Rainfall in early 2012 has lessened the intensity of the current drought, but below average rainfall and above average temperatures are forecasted for the summer of 2012 (LCRA 2012, p. 1).

In summary, the effects of climate change could potentially lead to detrimental impacts on aquifer-dependent species, especially coupled with other threats on water quality and quantity. However, there are little data available to correlate groundwater trends and climate change, and groundwater typically represents an integration of past climatic conditions over many years due to its time within an aquifer system (Mace and Wade 2008, p. 657). Recharge, pumping, natural discharge, and saline intrusion of groundwater systems could all be affected by climate change (Mace and Wade 2008, p. 657). Because climate change has the potential to negatively affect water quality and spring flow, we consider climate change to be

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