Where hidden water tables meet the Earth’s surface, life thrives even in the driest locations. Shallow groundwater aquifers act like water savings accounts, offering refuge during droughts. These aquifers provide moisture to support ecosystems even as precipitation dwindles. With climate change and human water use depleting groundwater levels worldwide, scientists and policymakers need better data on these groundwater-dependent ecosystems.
MAPPING GROUNDWATER-DEPENDENT ECOSYSTEMS
A new study maps these ecosystems in dry land regions globally, examines their protection status, and explores their overlap with human communities. Published in the journal Nature, this study marks the first time groundwater-dependent ecosystems have been mapped on a global scale. Researchers from universities, non-profits, and institutions from seven countries, including UC Santa Barbara, contributed to this effort. Their results show that 53% of these ecosystems are in areas with known groundwater depletion, while only 21% exist in protected lands or regions with protective policies.
THE ROLE OF TECHNOLOGY IN MAPPING
The research team used six years of data from NASA’s Landsat satellite to estimate leaf water content, evapotranspiration, vegetation greenness, open water, land temperatures, and climate data. They trained a computer model with over 30,000 data points of confirmed groundwater-dependent ecosystems to identify these areas based on satellite data.
“This global analysis builds on our work on riparian resilience,” said Kelly Caylor, co-author and geography professor at UCSB. “Our approach leverages what we know about these ecosystems.”
RESULTS AND IMPLICATIONS
The study resulted in a global map of groundwater-dependent ecosystems from 2015-2020, with a statistical likelihood of groundwater dependence for each location. The model’s accuracy is estimated at around 87%. “Our map is a starting point,” said lead author Melissa Rohde, an ecohydrologist and environmental consultant. “It provides essential information on where these ecosystems are likely located and most at risk of groundwater depletion.”
GROUNDWATER-DEPENDENT ECOSYSTEMS AND BIODIVERSITY
Ecosystems that depend on groundwater vary widely, from desert springs to mountain meadows and coastal wetlands. These ecosystems are often biodiversity hotspots and are increasingly threatened by climate change and human exploitation. Without data, conservation efforts are hindered. “These ecosystems rely on groundwater, but their dependence has been unacknowledged,” Rohde said.
PROTECTION STATUS AND HUMAN IMPACT
The study found that groundwater-dependent ecosystems are more intact in Central Asia, the Sahel region of Africa, and South America, where pastoral communities are common. In contrast, they are depleted and fragmented in regions like North America and Australia, where groundwater pumping and agricultural irrigation prevail.
CONSERVATION CHALLENGES AND SOLUTIONS
To highlight these ecosystems’ importance in supporting rural livelihoods, the study focused on the Greater Sahel region of Africa. Here, conflict hotspots overlap with high numbers of groundwater-dependent ecosystems. Climate change exacerbates food insecurity, leading to crop cultivation in pastoral lands. This demonstrates the need to recognize complex interactions between climate change and land and water conservation efforts.
CASE STUDY: THE GREATER SAHEL REGION
“These ecosystems impact rural livelihoods,” Rohde said. “Sustainable groundwater management policies may be feasible in some regions, but humanitarian assistance might be more appropriate in others.” Creative solutions are necessary, varying by region.
THE NEED FOR BETTER GROUNDWATER MANAGEMENT
Despite finding that 21% of groundwater-dependent ecosystems have some protection, the team noted that few ecosystems are effectively protected. “We need to acknowledge groundwater’s critical role for many ecosystems,” Rohde said. “Groundwater is being pumped faster than it can be replenished, and we aren’t managing it sufficiently to prevent ecosystem impacts.”
To achieve global biodiversity and climate goals, we must connect groundwater and ecosystem conservation efforts. Effective groundwater management is crucial for protecting these vital ecosystems and the communities that depend on them.
