Grantee Research Project Results
Final Report: Interactions Among Climate, Humans and Playa Wetlands on the Southern High Plains
EPA Grant Number: R829641Title: Interactions Among Climate, Humans and Playa Wetlands on the Southern High Plains
Investigators: McMurry, Scott T. , Willis, D. B. , Smith, L. M. , Dayawansa, W. P.
Institution: Towson University
EPA Project Officer: Packard, Benjamin H
Project Period: July 1, 2002 through June 30, 2005 (Extended to June 30, 2006)
Project Amount: $900,000
RFA: Assessing the Consequences of Global Change for Aquatic Ecosystems: Climate, Land Use, and UV Radiation (2001) RFA Text | Recipients Lists
Research Category: Climate Change , Ecological Indicators/Assessment/Restoration , Water , Aquatic Ecosystems
Objective:
We hypothesized that climatic variability (e.g., temperature shifts), and past, current, and future land use practices (e.g., crop production, native grassland) dictate hydroperiod and spatial distribution of wet playas (playas that contain water). This, in turn, influences the ecological structure of vegetation and animal communities that rely on playa lakes for many life history requisites. Our objectives were to: (1) determine the structure and composition of floral, amphibian, and avian communities in different playa wetland systems; (2) classify the playa system according to the hydroperiod and spatial distribution of wet playas using climatic, soil, and geomorphic data; (3) study population dynamics of vegetative, amphibian, and avian community composition in response to hydroperiod and spatial distribution of wet playas as emergent properties of objectives 1 and 2; and (4) study effects of long-term (50 years) changes in climate (temperature and rainfall amounts and patterns) on hydroperiod and distribution of playas and responses of biota requiring playa wetlands.
Summary/Accomplishments (Outputs/Outcomes):
Our results demonstrate that land use surrounding playa wetlands has a significant effect on playa condition and function. Sediment depth and percentage volume loss were greater in playas surrounded predominantly by cropland compared to grassland, yet hydroperiod was essentially equal between landuse types. Although sediment loads in playas do influence hydroperiod, it can also be influenced to a large degree by other factors, including watershed size and slope, and total amount and frequency of precipitation. These factors are difficult or impossible to control. In contrast to sediment depth and volume loss, percentage vegetation cover and plant richness were lower in cropland dominated playas. This may be due to hydrological differences between landuse types, as well as heavy sediment loads in cropland playas that bury seed banks.
Amphibian community richness was not sensitive to landuse per se. But it was sensitive to hydroperiod, as species dropped out of the community when hydroperiod dropped below 100 days. Further, the loss of species was not random. Species with longer larval development periods, and those species typically less abundant in the community, disappeared from playas with shortened hydroperiods. Akaike’s Information Criterion (AIC) model results indicated that amphibian community richness was driven mostly by hydroperiod, landuse, and playa density. Playa density will likely become more important as playas continue to fill with sediments, eventually fossilizing playas and rendering them non-functional. Fossilization of playas reduces the number of playas available to amphibians for successful reproductive efforts. A reduced number of nearby playas are available to breeding and migrating amphibians because playas do not consistently collect or retain water each year, thereby decreasing playa density through natural processes. An additional reduction in potential playas due to fossilization will likely further reduce the number of available playas. Models of species richness related to playa density had substantial support using AICc, indicating that species richness is dependent on surrounding playas. Presence of surrounding wetlands is crucial for maintaining juvenile dispersal, habitat connectivity, gene flow, and metapopulation dynamics.
At high rates of sedimentation, an increasing number of playas are expected to be fossilized and reduce the number of available habitat patches for amphibian species. Amphibian dispersal distances are generally only a few hundred meters (<300 m), although some species travel much farther. Thus, dispersing individuals must rely on their natal playa and the limited number of nearby playas. Thus, increasing the distance to the nearest wetland likely will reduce the number of dispersing juveniles. Reduced migration between playas can alter metapopulation dynamics as well as limit gene exchange. Amphibian species suffering from diminished gene flow may be more susceptible to disease, pollution, arrival of invasive species, and, ultimately, extinction.
Avian community richness was positively related to playa area, water depth, and tilled index (a measure of landuse). Unlike amphibians, birds are quite mobile and thus less restricted to particular playas. Thus, they likely respond differently than amphibians to different characteristics of playas. Overall, birds favored large playas with deeper water, a relationship with important conservation implications. Playa size is related to region, as indicated by larger playas in the fine textured soil zone in the northern portion of the study area. Therefore, protection of these playas would help maximize avian species richness in the Southern High Plains (SHP). Interestingly, avian species richness was also somewhat positively related to tilled index (greater proportion of cropland). However, this response did appear to be due to an increase in exotic bird species in cropland playas.
Our research on playa wetland ecology in the SHP is in large part directed toward understanding the influence of anthropogenic stress on playa function and associated biota. Two major stressors are constantly at play in this ecosystem: agriculture and climate. Agricultural stresses include pesticides (for which little is known) and sedimentation (likely the most significant threat). Results of our study, and those of others, clearly show individual, population, and community level responses for amphibians and birds related to local and landscape level variables (e.g., hydroperiod, playa area, playa density, etc.). These variables are often tied to broader landuse practices surrounding playas (i.e., agriculture). For example, although playa density varies naturally, continuous deposition of sediments into cropland playas has, and will continue to, bury their hydric soil defined basins. Eventually, these playas will be completely buried, non-functional, and effectively eliminated from the landscape. This phenomenon has already happened to many playas on the SHP.
Climate in the SHP is characterized by seasonally intense and patchy rainfall events, with most precipitation occurring in May and June. Many playas within a given year will receive enough precipitation to support hydroperiods capable of supporting the feeding and breeding requirements of avian and amphibian communities. However, many will not. Most climate change predictions for the SHP call for minimal changes in precipitation, although annual mean temperature may increase by 1 to 5°C.
As shown, sedimentation is greater in cropland than grassland playas, which results in reduced hydroperiods in cropland playas, all else being equal (watershed, rainfall, etc.). Model simulations (Agricultural Policy/Environmental Extender [APEX]) predict that the number of wet days from May through August will differ dramatically between cotton (the dominant crop) and grassland playas. Simple mitigation strategies such as furrow diking and buffer strips slow sedimentation and, in some cases, water flow into cropland playas. However, ultimately, cropland playas still lose significant wet days at the end of 50 years. In addition, although increases in annual mean temperature appear to add to the negative effects of sedimentation on hydroperiod, eventually sediment loads drive playa function and persistence. As playas continue to fill with sediment, they will eventually become fossilized and incapable of holding water for any significant period of time. The response will likely follow a predictable spatial pattern from south to north (following the natural gradient of climate and soil texture). So, continued sedimentation of playas and increased temperatures will result in a predictable loss of species from amphibian communities and, ultimately, effects on avian communities. Given that cropland playas will be the first to succumb to these stressors and that they represent the bulk of playas on the SHP, the end result will be significant deleterious effects on biotic diversity across the Southern Great Plains.
Journal Articles on this Report : 12 Displayed | Download in RIS Format
Other project views: | All 18 publications | 12 publications in selected types | All 12 journal articles |
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Anderson T, Salice C, Erikson R, McMurry S, Cox S, Smith L. Effects of landuse and precipitation on pesticides and water quality in playa lakes of the southern high plains. CHEMOSPHERE 2013;92(1):84-90. |
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Grandmaison DD, Niemi GJ. Local and landscape influence on red-winged blackbird (Agelaius phoeniceus) nest success in Great Lakes coastal wetlands. Journal of Great Lakes Research 2007;33(Suppl 3):292-304. |
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Gray MJ, Smith LM, Brenes R. Effects of agricultural cultivation on demographics of Southern High Plains amphibians. Conservation Biology 2004;18(5):1368-1377. |
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Gray MJ, Smith LM, Leyva RI. Influence of agricultural landscape structure on a Southern High Plains, USA, amphibian assemblage. Landscape Ecology 2004;19(7):719-729. |
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Gray MJ, Smith LM, Miller DL, Bursey CR. Influences of agricultural land use on Clinostomum attenuatum metacercariae prevalence in Southern Great Plains amphibians, U.S.A. Herpetological Conservation and Biology 2007;2(1):23-28. |
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Smith L, Haukos D, McMurry S, LaGrange T, Willis D. Ecosystem services provided by playas in the High Plains:potential influences of USDA conservation programs. ECOLOGICAL APPLICATIONS 2011;21(3):S82-S92. |
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Tsai J-S, Venne LS, McMurry ST, Smith LM. Influences of land use and wetland characteristics on water loss rates and hydroperiods of playas in the Southern High Plains, USA. Wetlands 2007;27(3):683-692. |
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Tsai J, Venne L, McMurry S, Smith L. Vegetation and Land use Impact on Water Loss Rate in Playas of the Southern High Plains, USA. WETLANDS 2010;30(6):117-1116. |
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Tsai J, Venne L, McMurry S, Smith L. Local and landscape influences on plant communities in playa wetlands. JOURNAL OF APPLIED ECOLOGY 2021;49(1):174-181. |
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Venne LS, Cobb GP, Coimbatore G, Smith LM, McMurry ST. Influence of land use on metal concentrations in playa sediments and amphibians in the Southern High Plains. Environmental Pollution 2006;144(1):112-118. |
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Venne LS, Anderson TA, Zhang B, Smith LM, McMurry ST. Organochlorine pesticide concentrations in sediment and amphibian tissue in playa wetlands in the Southern High Plains, USA. Bulletin of Environmental Contamination and Toxicology 2008;80(6):497-501. |
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Venne L, Tsai J, Cox S, Smith L, McMurry S. Amphibian Community Richness in Cropland and Grassland Playas in the Southern High Plains, USA. WETLANDS 2012;32(4):619-629. |
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Supplemental Keywords:
water, watersheds, groundwater, land, soil, sediments, global climate, precipitation, effects, ecological effects, vulnerability, sensitive populations, animal, mammalian, population, stressor, susceptibility, ecosystem, indicators, restoration, regionalization, scaling, terrestrial, aquatic, habitat, alternatives, sustainable development, innovative technology, renewable, waste reduction, waste minimization, remediation, restoration, public policy, decision making, cost benefit, conservation, biology, ecology, hydrology, mathematics, zoology, modeling, monitoring, climate models, Great Plains, Southern High Plains, Texas, TX, New Mexico, NM, Oklahoma, OK, Colorado, CO, Kansas, KS, EPA Region 6, agriculture,, RFA, Scientific Discipline, Air, Water, Hydrology, Water & Watershed, climate change, Atmospheric Sciences, Ecological Risk Assessment, Watersheds, anthropogenic stress, water resources, anthropogenic processes, wetlands, environmental monitoring, global change, regional hydrologic vulnerability, agricultural watershed, hydrologic models, playa wetlands, climate models, agriculture, vulnerability assessment, temperature variables, land and water resources, landscape characterization, climate variability, Global Climate Change, land useRelevant Websites:
http://www.orgs.ttu.edu/waterinitiative/faculty/mcmurry.php Exit
http://www.orgs.ttu.edu/waterinitiative/faculty/lsmith.php Exit
Progress and Final Reports:
Original AbstractThe perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.