LONG-TERM CLIMATE CONTROLS ON WETLAND ECOSYSTEMS IN THE DESERT SOUTHWEST

Substantial landscape change has occurred in the western United States in the last 200 years as a result of human activity and climate change, including the ecosystems of the desert southwest. This study presents the results of paleoenvironmental reconstructions from desert wetlands (ciénegas) in the borderlands region of northern Sonora, Mexico, southern Arizona and New Mexico for the last 8000 years to present that provide the baseline for understanding these more recent changes. These reconstructions examine changes in fire, erosion, vegetation, woody plant encroachment and saturation of the soils. Hypothesized controls on the changes include long-term and recent climate change including ENSO and the monsoon, resulting changes in groundwater hydrology, changes in fire regime, changes in CO₂ concentrations, and fire suppression. The paleoecological data are being used by land management agencies, private land owners and non-profits for restoration of these critical desert habitats.