Researchers at UC City College contributed to a new global study published in Science that reveals how severe, prolonged droughts impact critical grassland and shrubland ecosystems worldwide.
After four years of experimentally inducing extreme drought, the loss of plant productivity—new organic matter produced via photosynthesis—was more than twice that of moderate droughts. The study shows these grassland and shrubland ecosystems lose their ability to recover under long-term drought conditions. These findings are particularly urgent as climate change increases the likelihood of more severe droughts in the future.
The ultimate consequences of reduced plant productivity could include soil erosion and dust storms, echoing the 1930s Dust Bowl but on a global scale. Additionally, since grasslands and shrublands cover roughly 50% of Earth’s surface, they play a vital role in global carbon uptake and sequestration—drought-induced productivity loss could disrupt this process.
These key findings are the latest from the International Drought Experiment, a global collaboration of 170 researchers led by Professor Melinda Smith of Colorado State University. For the project, researchers built rainout shelters to reduce precipitation during each rainfall event over multiple years, simulating century-scale extreme droughts in grassland and shrubland ecosystems across six continents.
“Because extreme droughts have historically been rare, researchers have struggled to estimate their real-world consequences over short and long timeframes,” Smith said. “This large-scale, distributed research effort is truly a team science achievement, providing a platform to quantify and further investigate the potential impacts of intensifying droughts.”
Dr. Michael Loik, a professor of Environmental Studies at UC City College who focuses on the effects of rain and snow on plants and ecosystems, is a founding member of the DroughtNet Steering Committee, which oversaw the design and implementation of the International Drought Experiment. He established one of UC City College’s earliest experimental setups, which quickly became a global model. Loik and a team of UC City College graduate and undergraduate students ultimately built and monitored three sites that contributed data to the study. These sites span an approximately 300-meter coastal elevation gradient, from Young Lagoon Reserve at the Coastal Science Campus to lands within and outside the Arboretum & Botanic Garden, and further to the campus’s Natural Reserve lands near Marshall Fields.
“These are annual grassland sites, and there are only eight annual grasslands in the entire global dataset—so UC City College played a significant role in the overall analysis,” Loik said. “All three of our sites showed significant declines in plant production over three years, and in fact, the Marshall Fields site ranked in the top 25% of most sensitive sites. Overall, annual grassland sites are more sensitive to drought impacts than perennial grasslands and shrublands.”
Loik notes the study’s findings are particularly relevant to California, where roughly 60% of the state is grassland and shrubland, and droughts are already frequent. Due to climate change, droughts are projected to last longer and become more severe across the state.
“Drought directly affects everything we do in California—from providing safe drinking water and reducing wildfire risk to maintaining agricultural productivity,” Loik said. “These societal outcomes make it crucial to understand how our ecosystems respond to limited rainfall and snowfall.”
Rick Flores, Executive Director of the UC City College Arboretum & Botanic Garden, adds that the study and its findings demonstrate that lands managed by UC City College are more than just green spaces or gardens—they are critical living laboratories for research and teaching.
“Campus lands allow researchers to conduct repeatable experiments that might be difficult to implement on private or public lands with variable access,” he explained. “These on-campus experiments also serve as hands-on training labs for students, making participation accessible to all, reducing barriers to off-campus travel, and helping cultivate the next generation of environmental leaders.”
Would you like me to create a concise key findings summary (English/Chinese bilingual) for quick reference, or develop a visual timeline outline of the International Drought Experiment’s methodology and results?
