Daily Rules, Proposed Rules, and Notices of the Federal Government
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This is a proposed rule to list the Austin blind salamander (
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.
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
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
(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.”
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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
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.
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.
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
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
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
Dispersal patterns through streams or aquifers for these four salamander species are relatively unknown. However, one study of other closely related
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
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.
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 (
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
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
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
The Jollyville Plateau salamander occurs in the Jollyville Plateau and Brushy Creek areas of the Edwards Plateau in Travis and Williamson Counties, Texas (Chippindale
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
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
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
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
The Salado salamander has reduced eyes compared to other spring-dwelling
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
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
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.
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
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
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.
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
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 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
Increases in impervious cover resulting from urbanization cause measurable water quality degradation (Klein 1979, p. 959; Bannerman
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.
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
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