Modeling sediment accumulation in North American playa wetlands in response to climate change, 1940–2100

Abstract

Playa wetlands on the west-central Great Plains of North America are vulnerable to sediment infilling from upland agriculture, putting at risk several important ecosystem services as well as essential habitats and food resources of diverse wetland-dependent biota. Climate predictions for this semi-arid area indicate reduced precipitation which may alter rates of erosion, runoff, and sedimentation of playas. We forecasted erosion rates, sediment depths, and resultant playa wetland depths across the west-central Great Plains and examined the relative roles of land use context and projected changes in precipitation in the sedimentation process. We estimated erosion with the Revised Universal Soil Loss Equation (RUSLE) using historic values and downscaled precipitation predictions from three general circulation models and three emissions scenarios. We calibrated RUSLE results using field sediment measurements. RUSLE is appealing for regional scale modeling because it uses climate forecasts with monthly resolution and other widely available values including soil texture, slope and land use. Sediment accumulation rates will continue near historic levels through 2070 and will be sufficient to cause most playas (if not already filled) to fill with sediment within the next 100 years in the absence of mitigation. Land use surrounding the playa, whether grassland or tilled cropland, is more influential in sediment accumulation than climate-driven precipitation change.

Using Remotely Sensed Imagery to Document How Land Use Drives Turbidity of Playa Waters in Texas

“…Playas are shallow, typically <2 m in depth [7], although urban playas are often deepened for recreation or flood management to depths > 3 m. It is thus possible that shallower playas (i.e., those associated with non-urban land-use types) may have been scored as turbid more frequently than warranted because the basin (the ground) could be seen through clear but shallow water. However, our results support the model predictions of Burris and Skagen [31], who estimated that most playa basins in our focal region would have been filled with sediments prior to 2010. It should be noted that their study was parameterized with Luo's [16] 40 playa soil samples from Texas (20 cropland, 20 pasture/grassland) and then extrapolated across the entire playa region.…”

“…Burris and Skagen [31] predicted that, based on past and current sedimentation rates in cropland and grassland playas, almost 90% of playas in the Great Plains (75% in Texas) would be completely infilled with sediments by 2100, and that this was more influenced by projected land use than by projected changes in precipitation. Sedimentation is effectively irreversible without anthropogenic intervention [69].…”

“…In both of these studies, land conversion for tillage agriculture was implicated as the ultimate cause of sediment accumulation that led to basin infill and impaired ability to pond water. As a consequence, sedimentation from land conversion has been deemed a more serious threat to playas than a 5˝C rise from climate change [30] or climate change-driven shifts in precipitation amount and intensity [31]. Indeed, a significant number of playas have already been estimated to be filled with sediment, with most playas projected to be filled completely within a century if no mitigation is done [31].…”

Southern Great Plains Rapid Ecoregional assessment—Volume I. Ecological communities

“…Although characterized by frequent, low-intensity fires, more intense fires may have occurred after pulses of vegetative growth followed by severe drought Smith, 2003). Since European settlement, human influences including fire suppression, grazing practices, invasive species, agricultural conversion, and groundwater withdrawal in surrounding watersheds have contributed to habitat fragmentation, altered hydrology, and increased accumulated sediments in basins (Smith, 2003;Burris and Skagen, 2013). Land uses surrounding playas, particularly cultivation of corn and wheat, can reduce inundation frequency, increase sedimentation, and alter hydroperiods compared to playas located in grasslands or pasture (Tsai and others, 2007;Collins and others, 2014).…”

Sediment Accumulation in Prairie Wetlands under a Changing Climate: the Relative Roles of Landscape and Precipitation

“…Many of these wetlands are completely surrounded by upland and are highly vulnerable to land conversion, habitat fragmentation, water pollution, ground-water withdrawal, and drought (Donald et al 1999;Gleason et al 2003;Tiner 2003). Sediment accumulation can also threaten the viability and hydrologic functioning of many wetlands embedded within the agricultural landscapes of the Great Plains (Smith et al 2011;Burris and Skagen 2012;Daniel et al 2014). For example, nearly 90 % of the shallow depressional wetlands, or playas, in the west-central Great Plains are predicted to completely fill with sediments by 2100 (Burris and Skagen 2012).…”