Drought can reshape ecosystems and cause long-lasting changes, like shifts in the composition of the area’s species and functions. Known as “ecological transformations,” these changes include forests becoming grasslands or salt marshes turning into mudflats. As climate change alters drought patterns, these transformations are expected to become more common, presenting challenges for natural resource managers who are not accustomed to managing the transformed landscape. 

A new publication in BioScience, led by Northern Rocky Mountain Science Center Biologist Wynne Moss co-authored by Southeast, North Central, South Central, and Alaska CASC researchers, with funding support from the National, Alaska and North Central CASCs, explores how drought can cause ecological transformations. The authors highlight examples from various terrestrial ecosystems, including Alaskan boreal forests, California chaparral, and Amazonian forests. 

The researchers examined ways drought can transform the dominant vegetation in ecosystems by affecting processes like mortality, growth rates, recruitment, and competitive dynamics. They also highlight how shifts in drought severity or frequency can lead to transformations. For example, more frequent droughts have already led to transformations where slow-growing tree species experience a second drought while still recovering from the first. The study also emphasizes different ways that drought interacts with landscape features, land use, invasive species, pests, grazing, and fire to cause transformations, and how these interactions could make future transformations more likely. 

To better prepare and manage for ecological transformations, the researchers suggest three general directions for future research and management: First, studying long-term drought impacts, specifically those that persist after the drought ends. One way to do this would be to revisit locations of previous studies to assess long-term dynamics and to identify early signs of major changes. Second, studying shifts in species composition after drought. Understanding which species are most likely to be harmed or helped by drought can help predict ecological changes and guide useful interventions for managers. Finally, comparing the responses of different ecosystem types to the same drought events or experimental conditions can be useful for understanding how risk of transformation varies across different ecosystems.  

Unlike other extreme events that can cause ecological transformations, drought is expected to occur widely, even in locations where average yearly precipitation will increase. This CASC-supported research can help managers prepare for different possible outcomes of drought.   

Read additional coverage of this publication, “21st-Century Droughts Are Transforming Ecosystems” on drought.gov.   

The article, published in the journal BioScience, is titled “Drought as an emergent driver of ecological transformation in the twenty-first century.”  CASC Authors on the publication include Jennifer Cartwright (Southeast CASC), Imtiaz Rangwala and Brian Miller (North Central CASC), Caitlin Rottler (South Central CASC), and Jeremy Littell (Alaska CASC).