Understanding Playas: Value, Threats, and Restoration
What is a playa? Do playas REALLY recharge the aquifer? What are the long-term threats to playas? We often get asked where people can find more information and research about playas, so we compiled our Top 10 list of papers you should read. These scientific papers describe the biological and societal value of playas, their overall and specific threats, and some of the programs that can help restore and conserve this critical wetland habitat.
Due to copyright law, we can only provide the abstracts, but links to download or purchase the full paper are provided. If you have any questions, contact PLJV Conservation Science Coordinator, Anne Bartuszevige, at 303-926-0777.
The Importance of Playa Wetlands to Biodiversity of the Southern High Plains
This is a seminal paper detailing the benefits to biodiversity bestowed upon the Southern High Plains by playas. The Southern High Plains have been described as “the largest featureless level landscape in North America,” with playas often representing the only noteworthy feature present across this expanse. As such, playas provide a rich accumulation of nutrients and variable habitat resulting in their status as a premier source of biodiversity in the region. Species richness extends to mammals, birds, reptiles, invertebrates, and plants. The authors also provide a detailed account of the formation and status of these ephemeral wetlands, starting with the formation of the plains millions of years ago and continuing through the creation of the watersheds that feed playas with runoff from precipitation to the current threats to playas attributed to expansive conversion of the plains to cropland and grazing areas. While the information contained in this article has been updated since its publication in 1994, this article remains one of the most seminal and highly cited publications detailing playas to date.
Protein and Energy Production in Playas: Implications for Migratory Bird Management
In this publication, energy production of playas is examined and quantified in terms of seed and invertebrate production. This energy production is compared between managed and unmanaged wetlands to provide clear management recommendations to increase the number of duck energy days produced per playa. Duck energy days, the amount of energy used to sustain one duck for one day, are explored and used to refocus conservation on bird population management. The idea of duck energy days is one highly valued and used by PLJV.
Influence of Land-use and Conservation Programs on Wetland Plant Communities of the Semiarid United States Great Plains
There are numerous programs designed to protect and conserve playas; this paper reviews the effects of one of the most prodigious of these programs, the USDA Conservation Reserve Program (CRP), which provides monetary landowner incentives for planting perennial non-crop cover on highly erodible wetlands. While the program has encouraged conservation of wetlands and has resulted in an improvement in wetland water retention in comparison to non-CRP influenced cropland playas, the non-native perennial tall grass species propagated by the CRP reduce runoff and inundation to playas as compared to playas populated with native shortgrass species. The authors also make a strong case for the prohibition of plowing playas when they are dry.
O’Connell, J. L., Johnson, L. A., Smith, L. M., Mcmurry, S. T., & Haukos, D. A. (2012). Influence of land-use and conservation programs on wetland plant communities of the semiarid United States Great Plains. Biological Conservation, 146, 108–115.
Ecosystem Services Provided By Playa Wetlands in the High Plains: Potential Influences of USDA Conservation Programs and Practices
This publication provides an overview of the ecological services playas provide to their ecosystems: increased plant and animal biodiversity, support for millions of migrating birds, and floodwater attenuation to name a few. The authors detail existing government programs that have been used or were created to facilitate the conservation of wetlands in cropland and prairie areas. The benefits and drawbacks of these programs are discussed, with a focal point being the injurious effects of planting tall non-native grasses around playas as a method of conservation. The growth characteristic of non-native grasses (their height and tendency to grow more densely than native species, primarily) result in decreased runoff and water accumulation in playas. Adverse impacts of sediment accumulation attributed to agricultural activity are also detailed. Recommendations for future conservation efforts are offered, focusing primarily on the planting of native shortgrass species in the place of non-native grasses, the creation of a native grass buffer zone around playa perimeters, and the removal of accumulated sediment.
Smith, L., Haukos, D., McMurry, S., LaGrange, T., & Willis, D. (2010). Ecosystem Services Provided By Playa Wetlands in the High Plains: Potential Influences of USDA Conservation Programs and Practices. Ecological Applications, 21(3), 82–92.
Review: Recharge Rates and Chemistry Beneath Playas of the High Plains Aquifer
This is a seminal paper on the hydrology of playas. The authors collate findings from 175 publications to synthesize a consistent description of the important recharge processes of the High Plains (Ogallala) aquifer and related hydrological processes of playas. The authors enhance the context of their findings by providing detailed information describing the quantities of water drained from the aquifer in comparison to recharge rates of water filtered through playas. Specific descriptions of the mechanisms that govern aquifer recharge and playa hydrology are illustrated in great detail. This comprehensive review finds that playas represent faster pathways for aquifer recharge by 1-2 orders of magnitude than more impermeable interplaya areas, such as cropland. “The physical characteristics of playas that have apparent influence on recharge rates are the drainage area, playa volume, depth of the playa floor, vertical extent of shrink- and-swell clay that lines playa floors, depth of sediment overlying clay-lined floors, unsaturated-zone sediments underlying the playa, and depth to the water table.” Accumulated sediments in playas reduce recharge rates.
Physical Loss and Modification of Southern Great Plains Playas
This paper investigates the rapid loss of playas that has taken place in the Southern Great Plains over the nearly four decades prior to its publication. Between 1970 and 2008, 38% of playas were found to have been lost; that is a 1% annual rate of loss of all playas in the study area. This loss is primarily caused by modification and destruction of playas to facilitate conversion to cropland and grazing area. A pervasive cause of playa loss is the accumulation of sediment brought into playas from developed cropland. This layer of sediment accumulates on top of the hydric soils and clay underlayer at the bottom of the playa, reducing production by inhabitants and inundation to the aquifer. The physical loss of playas due to sediment accumulation covering and filling the wetland basin is estimated to be 14,607 playas. Playas are further injured by intentional modifications, the most common being pitting, trenching, or tilling. All three of these modifications dramatically alter the hydrological properties of playas, which are their most defining features. The article concludes with a summary of the dire situation for playas, and a call for better legislation aimed at safeguarding playas against future modification and extirpation.
Effects of Sedimentation on Playa Wetland Volume
This is a seminal article detailing the effects of cropland on sediment accumulation in playas in the Southern High Plains, with suggestions for conservation strategies to prevent further damage. Sediment buildup is greater in playas whose watershed is dominated by cropland as compared to rangeland. When surveyed, 18 of 20 playas in cropland-dominated watersheds had lost all of their original basin volume. The rangeland playas also experienced increased sediment accumulation due to nearby cropland cultivation. Comparison to a purely rangeland watershed was not possible due to the heavy cultivation of the area.
Sedimentation of Nebraska’s Playa Wetlands: A Review of Current Knowledge and Issues
While technically not a peer reviewed article, this report well summarizes the current understanding of sedimentation of playas. The effects and mechanisms of sediment accumulation are well documented and shown with pictures that provide valuable context to the more general explanations of the ecological principles at hand. In addition, the authors describe Nebraska’s playas, summarize data on historical and recent wetland soil profiles, describe the impact that culturally accelerated sedimentation has on numerous wetland functions, and provide recommendations on restoration approaches.
LaGrange, T.G., R. Stutheit, M. Gilbert, D. Shurtliff, and P.M. Whited. 2011. Sedimentation of Nebraska’s Playa Wetlands: A Review of Current Knowledge and Issues. Nebraska Game and Parks Commission, Lincoln. 62 pages. Accessed April 27, 2017.
Ecosystem Services Provided by Waterbirds
This article does an excellent job of providing one thing many more general articles about specific components of conservation lack: context. The authors examine the conservation of waterbirds in the context of the ecosystem services provided by these birds and provide economic values for easier understanding of the actual value of these ecosystem services. Key services investigated include cultural services such as birding tourism, harvest value from hunting and farming, support of biodiversity of non-avian taxa, their use as bioindicators of ecosystem health and general disease surveillance, nutrient cycling, and pest control. By providing a value to these services, playa conservation programs that positively impact waterbird populations can make a stronger argument for the need to implement conservation efforts.
The Empirics of Wetland Valuation: A Comprehensive Summary and a Meta-analysis of the Literature
While not a paper that strictly deals with playas, this paper provides an exhaustive meta-analysis of work done to empirically value wetlands in the 25 years preceding its publication. This valuation provides information useful to those who would make a case for the non-biological benefits for wetland restoration worldwide. While the broad scope of this article precludes it from providing a strict valuation of individual wetlands, it lays out why wetlands should be valued for more than just the biological benefits they provide. These values are broken down by activity component, which presents a useful comparison for which pieces provide the greatest value to a wetland.
Brander, L. M., Florax, R. J. G. M., & Vermaat, J. E. (2006). The empirics of wetland valuation: A comprehensive summary and a meta-analysis of the literature. Environmental and Resource Economics, 33(2), 223–250.