Climate & Sustainability
Could climate change create a new dust bowl?
International Drought Experiment shows severe impacts of extreme, prolonged drought
Researchers at UC Santa Cruz contributed to a new global study published in Science that reveals how severe, long-term drought affects crucial grassland and shrubland ecosystems around the world.
Losses in plant productivity – the creation of new organic matter through photosynthesis – were more than twice as high after four years of experimentally induced extreme drought when compared to losses from droughts of moderate intensity. The work shows that these grassland and shrubland ecosystems lose their ability to recover over time under prolonged dry conditions. The findings are particularly relevant as climate change increases the possibility of more severe droughts in the future.
The eventual results of such losses in plant productivity could include soil erosion and dust storms, a situation that echoes the Dust Bowl of the 1930s, but on a global scale. Also, because grasslands and shrublands cover roughly 50% of the Earth’s surface, they play a large role in balancing and facilitating carbon uptake and sequestration globally. That could be disrupted by drought-induced productivity losses.
These crucial findings are the latest results from the International Drought Experiment, a global group of 170 contributing researchers led by Professor Melinda Smith at Colorado State University. For the project, researchers built rainfall manipulation structures that reduced each rainfall event over a multi-year period to simulate 1-in-100-year extreme drought conditions in grassland and shrubland ecosystems across six continents.
“Because of the historic rarity of extreme droughts, researchers have struggled to estimate the actual consequences of these conditions in both the near and long-term,” Smith said. “This large, distributed research effort is truly a team effort and provides a platform to quantify and further study how intensified drought impacts may play out.”
Local research sites support global findings
UC Santa Cruz Environmental Studies Professor Michael Loik, whose research focuses on the effects of rain and snow on plants and ecosystems, was a charter member of the steering committee for DroughtNet, which oversees design and implementation of the International Drought Experiment. He built one of the first experimental setups at UC Santa Cruz that quickly became a global model.
Loik and a team of UC Santa Cruz graduate and undergraduate students ultimately established and monitored three sites that contributed data to the current study. The sites are placed along a roughly 300 meter coastal elevation gradient, from Younger Lagoon Reserve on the Coastal Science Campus to just outside the Arboretum and Botanic Gardens and up into Campus Natural Reserve lands near Marshall Fields.
“These are annual grassland sites, and there were only eight annual grasslands in the entire global dataset, so UC Santa Cruz had an important role in the overall analysis,” Loik said. “All three of our sites showed a significant drop in plant productivity over three years, and in fact the Marshall Fields site was in the top 25% of most sensitive sites. In general, the annual grassland sites were more sensitive to drought over time compared to perennial grasslands and shrublands.”
The study’s findings have particular significance for California, Loik says. The state is about 60% grassland and shrubland and already frequently experiences drought conditions. Droughts are expected to last longer and become more severe in the state due to climate change.
“Drought directly impacts everything we do in California, such as providing safe drinking water, reducing wildland fire risk, and maintaining agricultural productivity,” Loik said. “These societal outcomes make it critically important to understand how our ecosystems respond to limited rain and snowfall.”
Rick Flores, Executive Director of UC Santa Cruz’s Arboretum & Botanic Garden, says the study and its findings also demonstrate how UC Santa Cruz’s managed lands are not just green space or gardens, but living laboratories that are critical infrastructure for research and teaching.
“Campus lands let researchers run repeatable experiments that could be hard to do on private or public lands with variable access,” he explained. “These experiments on campus lands also become hands-on training labs for students, making it accessible for all students, reducing the barriers associated with off-campus travel, and helping to train the next generation of environmental leaders.”