Global Groundwater Analysis Shows Demand Outstrips Supply
Almost one-quarter of the world’s population lives in regions where groundwater is being used up faster than it can be replenished, concludes a comprehensive global analysis of groundwater depletion, published this week in Nature.
Across the world, human civilizations depend largely on tapping vast reservoirs of water that have been stored for up to thousands of years in sand, clay and rock deep underground. These massive aquifers—which in some cases stretch across multiple states and country borders—provide water for drinking and crop irrigation, as well as to support ecosystems such as forests and fisheries.
Yet in most of the world’s major agricultural regions, including the Central Valley in California, the Nile delta region of Egypt and the Upper Ganges in India and Pakistan, demand exceeds these reservoirs' capacity for renewal.
“This overuse can lead to decreased groundwater availability for both drinking water and growing food,” says Tom Gleeson, a hydrogeologist at McGill University in Montreal, Quebec, and lead author of the study. Eventually, he adds, it “can lead to dried up streams and ecological impacts."
Gleeson and his colleagues combined a global hydrological model and a data set of groundwater use to estimate how much groundwater is being extracted by countries around the world. They also estimated each aquifer's rate of ‘recharge’—the speed at which groundwater is being replenished. Using this approach, the researchers were able to determine the groundwater ‘footprint’ for nearly 800 aquifers worldwide (see map above).
In calculating how much stress each source of groundwater is under, Gleeson and colleagues also looked in detail at the water flows needed to sustain the health of ecosystems such as grasses, trees and streams.
“To my knowledge, this is the first water-stress index that actually accounts for preserving the health of the environment,” says Jay Famiglietti, a hydrologist at the University of California, Irvine, who was not involved in the study. “That’s a critical step.”
The authors found that 20 percent of the world’s aquifers are being overexploited, some massively so. For example, the groundwater footprint for the Upper Ganges aquifer is more than 50 times the size of its aquifer, “so the rate of extraction is quite unsustainable there," says Gleeson.
Yet Famiglietti notes that the study, which focuses on quantifying the rate of groundwater tapping versus recharging, underscores the lack of data we have on the amount of water currently in the world's aquifers. “The only way to answer the sustainability question is to answer how much water we actually have,” he says.
He predicts that a comprehensive picture would reveal that many more of the world’s aquifers are being tapped unsustainably. As certain regions face more frequent droughts and population growth, full characterization of aquifers worldwide, although expensive, will be necessary, adds Famiglietti.
But Gleeson adds that there is at least one significant source of hope. As much as 99 percent of the fresh, unfrozen water on the planet is groundwater. “It’s this huge reservoir that we have the potential to manage sustainably,” he says. “If we choose to.”
Sweden's reindeer have a problem. In winter, they feed on lichens buried beneath the snow. But the climate crisis is making this difficult. Warmer temperatures mean moisture sometimes falls as rain instead of snow. When the air refreezes, a layer of ice forms between the reindeer and their meal, forcing them to wander further in search of ideal conditions. And sometimes, this means crossing busy roads.
- San Antonio, Texas Unveils Largest Highway Crossing for Wildlife in ... ›
- Wildlife Crossings a Huge Success - EcoWatch ›
EcoWatch Daily Newsletter
- Climate Change Will Be Sudden and Cataclysmic Unless We Act Now ›
- There's a Heatwave at the Arctic 'Doomsday Vault' - EcoWatch ›
- Marine Heatwaves Destroy Ocean Ecosystems Like Wildfires ... ›
By Aaron W Hunter
A chance discovery of a beautifully preserved fossil in the desert landscape of Morocco has solved one of the great mysteries of biology and paleontology: how starfish evolved their arms.
The Pompeii of palaeontology. Aaron Hunter, Author provided<h2></h2><p>Although starfish might appear very robust animals, they are typically made up of lots of hard parts attached by ligaments and soft tissue which, upon death, quickly degrade. This means we rely on places like the Fezouata formations to provide snapshots of their evolution.</p><p>The starfish fossil record is patchy, especially at the critical time when many of these animal groups first appeared. Sorting out how each of the various types of ancient starfish relate to each other is like putting a puzzle together when many of the parts are missing.</p><h2>The Oldest Starfish</h2><p><em><a href="https://www.biorxiv.org/content/10.1101/216101v1.full.pdf" target="_blank" rel="noopener noreferrer">Cantabrigiaster</a></em> is the most primitive starfish-like animal to be discovered in the fossil record. It was discovered in 2003, but it has taken over 17 years to work out its true significance.</p><p>What makes <em>Cantabrigiaster</em> unique is that it lacks almost all the characteristics we find in brittle stars and starfish.</p><p>Starfish and brittle stars belong to the family Asterozoa. Their ancestors, the Somasteroids were especially fragile - before <em>Cantabrigiaster</em> we only had a handful of specimens. The celebrated Moroccan paleontologist Mohamed <a href="https://doi.org/10.1016/j.palaeo.2016.06.041" target="_blank" rel="noopener noreferrer">Ben Moula</a> and his local team was instrumental in discovering <a href="https://www.sciencedirect.com/science/article/abs/pii/S0031018216302334?via%3Dihub" target="_blank" rel="noopener noreferrer">these amazing fossils</a> near the town of Zagora, in Morocco.</p><h2>The Breakthrough</h2><p>Our breakthrough moment came when I compared the arms of <em>Cantabrigiaster</em> with those of modern sea lilles, filter feeders with long feathery arms that tend to be attached to the sea floor by a stem or stalk.</p><p>The striking similarity between these modern filter feeders and the ancient starfish led our team from the University of Cambridge and Harvard University to create a new analysis. We applied a biological model to the features of all the current early Asterozoa fossils in existence, along with a sample of their closest relatives.</p>
Cantabrigiaster is the most primitive starfish-like animal to be discovered in the fossil record. Aaron Hunter, Author provided<p>Our results demonstrate <em>Cantabrigiaster</em> is the most primitive of all the Asterozoa, and most likely evolved from ancient animals called crinoids that lived 250 million years before dinosaurs. The five arms of starfish are a relic left over from these ancestors. In the case of <em>Cantabrigiaster</em>, and its starfish descendants, it evolved by flipping upside-down so its arms are face down on the sediment to feed.</p><p>Although we sampled a relatively small numbers of those ancestors, one of the unexpected outcomes was it provided an idea of how they could be related to each other. Paleontologists studying echinoderms are often lost in detail as all the different groups are so radically different from each other, so it is hard to tell which evolved first.</p>
- Biden Reaffirms Commitment to Rejoining Paris Agreement ... ›
- Biden Likely Plans to Cancel Keystone XL Pipeline on Day One ... ›
- Joe Biden Appoints Climate Crisis Team - EcoWatch ›