Land Protection Plan - Wyoming Toad Conservation Area/Chapter 3—Threats to and Status of Resources

by the United States Fish and Wildlife Service

Chapter 3—Threats to and Status of Resources

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© Bob Gress Prairie dog burrows and open patches of ground create habitat for several species, including mountain plover.

Threats to Resources

In the Laramie Plains, as in much of the West, communities tend to be located near riparian areas. Planning for expected development and other land use changes is needed for conserving wildlife habitat in the area. The Wyoming toad, along with an estimated 90 percent of the total wildlife species and 70 percent of bird species in Wyoming (Nicholoff 2003), uses wetlands and riparian habitats either daily or seasonally.

Development

Population growth in the State of Wyoming is expected to continue. Between 2000 and 2005, Wyoming ranked 31st in population growth, but from 2006 to 2007, Wyoming jumped to ninth in population growth (Hulme et al. 2009). From 1978 to 2007, total land in agriculture in Wyoming declined from 33.6 million acres to 30.2 million acres, a decrease of more than 10 percent. Albany County alone saw a 6-percent decrease in farm lands from 2002 to 2007 (USDA 2007). However, much of the residential growth in Wyoming is considered rural, with a housing density of 1 unit per 40 acres (Hulme et al. 2009). Increasingly, these exurban homes are often second homes. From 1990 to 2000, Wyoming saw a 30-percent increase in second home buying, and 7.2 percent of total housing units in Albany County are second homes. People are drawn to the open space, abundant wildlife, and recreational opportunities that are available, but exurbanization leads to increased habitat fragmentation and a shift from traditional agriculture practices.

Wyoming ranked seventh in production of crude oil and second in the production of natural gas in 2010, with production occurring throughout the State (Petroleum Association of Wyoming 2012). Also, Wyoming ranks 10th in the nation in proven reserves of crude oil and second in proven reserves of natural gas. Proven reserves are the amount estimated to be recoverable from well-established or known reservoirs. Because of high proven reserves within the State and the increased nationwide need for energy, oil and gas development is likely to continue throughout the State.

Over 43 percent of Wyoming has the potential for development of wind energy (U.S. Department of Energy 2011). Wyoming ranks 10th in potential wind energy development, with 27.3 million acres (42,631.28 square miles) of available land with an installed capacity of 552,072.6 megawatts and an annual generation of 1.9 million gigawatt-hours. Most of this potential is within the southeast part of the State. Most of the land with potential for wind development would still be available with the Wyoming Toad Conservation Area.

Fragmentation

Changes in land cover resulting from residential development, energy development, and roads not only cause a loss of habitat, they also fragment remaining habitat. There is a robust body of literature on the effects of habitat fragmentation that has been summarized by Collinge (2009). Countless manipulative and observational studies have shown that habitat area and connectivity between similar habitats are important at all trophic levels ranging from soil decomposers (Rantalainen et al. 2005) to passerine birds (Telleria and Santos 1995). Intact corridors between fragments promote use of, and persistence in, those habitats by migratory birds (Haas 2002), large carnivores (Shepherd and Whittington 2006, Tremblay 2001), and ungulates (Tremblay 2001) that are native to the WTCA. Perhaps the most obvious way to protect migration routes as well as valuable habitat in the WTCA is to focus on the conservation of the riparian corridors that cross and connect existing protected areas. This action would protect wildlife movement corridors for seasonal migration as well as colonization following large-scale disturbances or environmental change.

High flows on the Big Laramie River. FWS

Invasive Species

Increased human disturbance associated with development has also been shown to negatively affect adjoining habitat because of the introduction and establishment of invasive plant species. Invasive plants can have many detrimental effects, including displacement of native vegetation, alteration of nutrient cycling and soil chemistry, alteration of hydrology, increased erosion, and changes in fire regimes (Dukes and Mooney 2004). Collectively, such changes can have severe negative effects on wildlife habitat, such as reducing the quality of nesting and foraging areas.

Another invasive species that is threatening the Wyoming toad and other amphibian populations in the Laramie Plains is chytrid fungus. Mortality caused by this fungus has been documented in the Wyoming toad population at Mortenson Lake Refuge and is thought to be one of the main causes of the toad’s decline in the 1970s. However, toad populations have been sucessfully maintained recently despite the widespread presence of chytrid. Other diseases such as “white-nose syndrome” in bats and chronic wasting disease in cervids may also threaten the wildlife in the Laramie Plains, although these diseases have not been documented in the area to date.

Water Use

The Laramie River and its tributaries are the primary source of water in the area. Because the open plains receive little precipitation, most surface and ground water is a result of snowpack runoff from the surrounding mountains. The potential for wetland management, creation, and restoration is constrained by the applicable provisions of State water law. Water can be appropriated and applied only to a beneficial use recognized by the State of Wyoming, and though a considerable number of water rights have been approved by the Wyoming State Engineers Office, there is no formal list of approved or defined beneficial uses in Wyoming (Wyoming Joint Venture Steering Committee 2010). Without formal recognition of wildlife habitat creation, maintenance, enhancement, or management as a beneficial use in the State of Wyoming, the rulings for water appropriation can be inconsistent and can lead to wetland habitat loss that would directly affect wetland-dependent wildlife populations. As fragmentation increases, remaining habitats become geographically isolated and wildlife populations with limited dispersal abilities may potentially become genetically and spatially isolated.

Climate Change

Climate change has become one of the paramount conservation issues and management challenges. The term “climate” refers to the mean and variability of different types of weather conditions over time, with 30 years being a typical period for such measurements, although shorter or longer periods also may be used (Parry et al. 2007). The term “climate change” refers to a change in the mean or variability of one or more measures of climate (such as temperature or precipitation) that persists for an extended period, typically decades or longer, whether the change is because of natural variability, human activity, or both (Parry et al. 2007). Various types of climate change can have direct or indirect effects on species. These effects may be positive, neutral, or negative, and may change over time, resulting in different effects on species and associated habitats (Parry et al. 2007).

Mountain ecosystems in the western United States are expected to be especially sensitive to climate change. Data shows that many places in the Rocky Mountains have experienced three times the global average temperature increase over the past century. The magnitude of warming in the northern Rocky Mountains has been particularly significant, as shown by an 8-day advance in the appearance of spring phenological indicators since the 1930s (Cayan et al. 2001). The hydrologic regime in the northern Rockies has also changed in response to the shift in global climate, and is projected to experience further changes (Bartlein et al. 1997, Cayan et al. 2001, Stewart et al. 2004). Under global climate change scenarios, the mountainous areas of northwest Wyoming may eventually experience milder, warmer, wetter winters and drier summers (Bartlein et al. 1997). Furthermore, the pattern of snowmelt runoff may change, with a reduction in spring snowmelt (Cayan et al. 2001) and an earlier peak runoff (Stewart et al. 2004), resulting in relatively lower annual discharge during spring and summer.

There is no available information on the potential threats of climate change on the Wyoming toad, and there is no evidence of direct effects to the species at this time (USFWS 2013). Many species that are already listed as endangered or threatened may be particularly vulnerable to changes in climate; it is also recognized that, for some listed species, the likely effects may be positive or neutral. However, some studies have predicted that amphibians will be even more susceptible to climate change than bird or mammal populations because of their physiology; dependence on microhabitats and predictable hydrological regimes; limited dispersal abilities (Blaustein et al. 1994); and susceptibility to diseases that may be intensified by climate change (Pounds et al. 2006). Some models predict substantially larger changes in amphibian populations than in birds or mammals, based primarily on potential future range contractions and expansions. This multitude of projected impacts could exacerbate the current population declines of many amphibian species (Stuart et al. 2004). Many wetland and riparian habitats, such as those found within the boundary of the conservation area, are dependent on snowmelt from surrounding high-mountain ecosystems and are therefore expected to be more acutely affected by changes in runoff amount, timing, and quality than other habitats (Parry et al. 2007). Because the snowpack in high-elevation montane ecosystems directly affects the phenology of lower elevation watersheds, species associated with these systems may be more acutely affected than species in more temperate ecotypes.

For amphibians and reptiles, the timing of key ecological events is influenced by environmental conditions such as air and water temperatures and precipitation patterns. The timing of breeding, egg laying, metamorphosis, dispersal, and migration may shift in response to higher temperatures and changes in rainfall (Beebee 1995). As temperatures warm and the water in aquatic habitats becomes more variable, amphibians are likely to experience lower rates of survival to metamorphosis. Temperatures outside of their thermal optima can also cause physiological stresses (Gibbons et al. 2000). Because of their affinities to aquatic habitats and their small size, amphibians typically have relatively small home ranges and low dispersal rates (Duellman and Trueb 1994, Wells 2007), making them more vulnerable to changes in their environment. The Wyoming toad, in particular, is a glacial relict that is adapted to a cool montane climate with a reliably high spring runoff. As climate change shifts temperature and hydrologic profiles beyond their historical ranges of variability, it is reasonable to assume that the Wyoming toad will experience population stress.

Migratory waterbirds are similarly adapted to a particular range of climate-related habitat conditions, including the timing and amount of water provided by runoff as well as the phenology of plant emergence and growth. Again, as climate change causes these conditions to shift outside of their historical ranges of variability, populations of wetland and riparian birds are likely to be stressed in novel ways.

Adaptation, Mitigation, and Engagement

The Service’s strategic response to climate change involves three core strategies: adaptation, mitigation, and engagement (USFWS 2009). As the climate changes, the abundance and distribution of wildlife and fish will also change in response to changing habitat conditions. Some species will adapt successfully to a warming world, many will struggle, and others will disappear.

The exact changes in temperature and precipitation that the Laramie Plains will experience are unknown. Equally unknown are the responses of wildlife and habitats to these changes. For example, some species will be more vulnerable to climate change than others. To help fish and other wildlife species adapt, keeping large areas of intact wetlands, robust riparian corridors, and open spaces will become increasingly important. The project area provides an anticipatory, rather than a reactive, response.

Forests, grasslands, wetlands, and soils have a large influence on atmospheric levels of carbon dioxide. Carbon sequestration forms one of the key elements of mitigation. The World Resources Institute estimates that, of the global stock of carbon in terrestrial ecosystems, grasslands store approximately 34 percent, forests store approximately 39 percent, and agro-ecosystems store approximately 17 percent of the total (White et al. 2000). It is as important to protect existing carbon stores from further degradation as it is to sequester atmospheric carbon.

Historically, the destruction of wetlands through land use changes has had the largest effects on carbon fluxes and the resulting radiative forcing of North American wetlands. Radiative forcing is the measure of the amount that the Earth’s energy budget is out of balance. The primary effects have been a reduction in the ability of the wetlands to sequester carbon (a small to moderate increase in radiative forcing), oxidation of their soil carbon reserves on drainage (a small increase in radiative forcing), and reduction in methane emissions (a small to large decrease in radiative forcing). It is uncertain how global changes will affect the carbon pools and fluxes of North American wetlands (Bridgham et al. 2006). The WTCA project could secure the carbon already stored within the soils of the Laramie Plains by preventing the conversion of native vegetation to various types of development and thus preventing the carbon liberation that accompanies ground-disturbing development.

Engagement involves cooperation, communication, and partnerships to address the conservation challenges presented by climate change (USFWS 2009). The WTCA serves as a model for engagement by working with landowners, nongovernmental organizations, State agencies, and Federal agencies.

One of the key recommendations that came from a climate change workshop that was held by The Nature Conservancy was to coordinate management of shared resources. Given that some regions are experiencing warming more rapidly than others, natural resource managers would benefit by coordinating their activities with others who are managing common resources. Regional and coordinated management of shared habitat may be the only way to make sure that some habitat can be kept in a resilient state while other habitat transitions to a different state (Robles and Enquist 2010).

Taking action on these recommendations will be crucial for achieving conservation and management goals in the face of a changing climate. Reduced snowpack in the mountains combined with earlier seasonal melting caused by rising temperatures may increase the intensity and length of late summer droughts and reduce the availability of water, especially in the western United States. Finding enough water is becoming an increasingly difficult challenge for western fish and wildlife species. Spring is arriving earlier, and plants and animals are being found farther and farther north of their historical ranges in the U.S. Wildlife biologists are concerned that this will mean some migratory species may not arrive in their breeding habitats when, or where, their particular food sources are available.

Effects of the Wyoming Toad Conservation Area on the Natural and Human Environment

For a thorough discussion of the effects of the easement and fee-title acquisition program, see chapter 4 of the EA in this volume (appendix A).