A first-of-its-kind map of groundwater-dependent ecosystems has been developed by an international team of scientists.
From desert springs, mountain meadows and streams to coastal wetlands and forests, the interactive resource maps these diverse ecosystems globally, offering insights into their protection status and how they overlap with human communities.
Often hot spots for biological diversity, climate change and human water use are rapidly depleting groundwater levels around the world putting ecosystems under increasing threat, the researchers warn.
Their study, presented in Nature, shows over half (53%) of the ecosystems are in areas with known groundwater depletion, while only one in five (21%) exist on protected lands or regions with policies in place for their protection.
The team, led by The Nature Conservancy and the Desert Research Institute (DRI) with collaborators including researchers from Cardiff University, say scientists and policy makers need better data on where they exist to combat this depletion.
"Until now, the location of ecosystems that rely on groundwater has been largely unknown, hindering our ability to track impacts, establish protective policies, and implement conservation projects," the study's lead author ecohydrologist and environmental consultant Melissa Rohde said.
The team gathered six years of imagery from NASA's Landsat satellite, which provides critical information on vegetation greenness and land temperatures, to build the map.
This was combined with estimates from climate data on how water from the Earth's surface is transferred into the atmosphere, providing an indirect measure of vegetation that relies on groundwater.
More than 30,000 data points of confirmed groundwater-dependent ecosystem locations were also used to train a computer model how to identify them based on the satellite data.
This analysis takes advantage of the fact that an ecosystem supported by groundwater can be seen with satellite imagery as it remains greener, cooler, and wetter than other places throughout the dry season.
Professor Michael Singer, Deputy Director of the Water Research Institute at Cardiff University and one of the paper's co-authors, said: "Our approach is novel, since it indirectly incorporates globally available information that links vegetation to groundwater to identify these critical ecosystems that provide refuge to many plant and animal species."
The result is a global map of where ecosystems dependent on groundwater existed from 2015-2020.
"The intention of our map is that it be used as a starting point," adds Rohde who completed the research as part of her doctoral study at the State University of New York's College of Environmental Science and Forestry and work at The Nature Conservancy, co-supervised by Professor Singer.
It provides essential information on where they are likely located and most at risk of groundwater depletion, so that we can advance the protection of these biologically diverse ecosystems, and the societies dependent upon them.
The map shows these ecosystems are more intact and extensive in Central Asia, the Sahel region of Africa, and South America, where pastoral communities are common.
This contrasts with their depletion and fragmentation in parts of the world where groundwater pumping and agricultural irrigation reign, such as North America and Australia.
In the latter regions, many of these ecosystems have already been lost, as groundwater tables fall below the level where plant roots or streams can reach them.
Analysing this new ecosystem map in the context of conflict, pastoralism, and water management policies gives us a clear picture of the challenge in managing these delicate ecosystems, including pressures due to groundwater pumping to meet drinking water needs for people and livestock.
