Drought & Grazing Experiment: Understanding Impacts and Identifying Mitigation Strategies

Long-term Vegetation Change on the Colorado Plateau

Long-term Vegetation Change on the Colorado Plateau

The USGS & National Park Service scientists have been monitoring grasslands across a historic grazing gradient in Canyonlands National Park sites since 1996, including a grassland that has never been grazed by domestic livestock.  

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Chronic Drought Impacts on Colorado Plateau Ecosystems

Chronic Drought Impacts on Colorado Plateau Ecosystems

Warming and associated drying will have large effects on dryland plants & soils. In this long-term study (2010-present), we are examining the effects of moderate, but long-term chronic drought using a network of 40 experimental drought shelters.

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Colorado Plateau Extreme Drought in Grassland Experiment

Colorado Plateau Extreme Drought in Grassland Experiment

In drylands, short-term extreme droughts can have profound ecosystem effects. In this study, we are examining the impacts of extreme seasonal drought on grassland communities of the Colorado Plateau & recovery from drought. 

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Science Center Objects

Drylands (sometimes called ‘deserts’ or ‘arid and semi-arid' ecosystems) are defined by water scarcity.  Understanding how land-use activities may effect dryland ecosystems and dryland ecological processes is a high priority for land conservation and management. Grazing by domestic livestock (typically cattle but also sheep and goats) is the most widespread land-use in drylands globally and a large proportion of dryland residents can be characterized as subsistence agropastoralists. Improper grazing in drylands, particularly during drought, can negatively impact plant productivity, soil erosion, water capture, and downstream water quantity and quality. Of particular concern is potentially irreversible ecosystem changes brought about by these scenarios. 

Grazing by large domestic herbivores effects dryland ecosystems directly through selective removal of plant biomass and physical disturbance (hoof impact) and indirectly via feedbacks through altering plant composition, plant-soil feedbacks, and other processes.  Importantly, the direct effects of grazing—especially during drought—on plants and soils can disrupt or alter dryland ecosystem processes and result in profound, often irreversible, changes.  These concerns are especially great given the increased risk of multi-year droughts brought on by climate change, the high vulnerability of important forage species to warming environments, and the demonstrated low resilience of many sensitive dryland ecosystems to the combined impacts of grazing and drought.   

In this study, we are conducting experiments to shed light on how drought, disturbance, and grazing by domestic livestock interact.  In addition, we are testing if changes in grazing timing may reduce risk to rangelands during and following drought.  In this new experiment, we are looking at how drought and grazing act separately and in combination to influence the structure and function of dryland ecosystems. 

Structures intended to reduce rainfall in a dryland ecosystem

Example of the passive rainfall reduction shelters used to create experimental drought near Canyonlands National Park, Utah (April 2015)

(Credit: Mike Duniway. Public domain.)