Scientists Alarmed to Discover That Earth's Continents Are Drying Out

New research examining over 20 years of data captured by NASA's twin climate satellites, GRACE and GRACE-FO, has revealed an "unprecedented" level of water loss among the planet's continents, creating "mega-drying" regions across the northern hemisphere. 

One of these mega regions spans Europe, the Middle East, North Africa, and vast swaths of Asia. That should clue you in to the staggering scale of this phenomenon, which the scientists are calling terrestrial water storage (TWS) loss. Since 2002, the area of land experiencing water loss has been increasing by twice the size of California every year, according to the study, published in the journal Science Advances.

It's a grim discovery that will only exacerbate human civilization's woes as our rampant carbon emissions rush us towards a climate tipping point past which the worst effects of climate change — soaring temperatures, disappearing glaciers, coastal flooding, and large-scale die-offs in the natural world, to name a few — are believed to become irreversible. 

Ominously, about 75 percent of the global population lives in one of the 101 countries that have been losing freshwater over the past two decades, the researchers found. The trend, if unmitigated, could lead to famine, trigger climate migrations, and destabilize entire countries, they warn.

Terrestrial water storage isn't just lakes and other obvious sources of water. As the authors explain in the paper, it's the combined ice, snow, surface water, canopy water, soil moisture, and groundwater stored on land. Our continents are less a cup being emptied out and more a soggy sponge being squeezed.

Previous research stitched together an incomplete picture of TWS change, showing that dry regions were getting drier at the same time that wet regions were getting wetter. But a "major development has been the interconnection of several regional drying patterns and previously identified hot spots for TWS loss to form four continental-scale mega-drying regions," the researchers wrote in the study.

The upshot? It now appears that the dry areas are drying faster than wet areas are getting wetter — a net drying inexorably driving the planet toward a parched "Mad Max" future. 

Much of it is our own doing. As surface sources of water dry up, human societies, especially in arid regions, have become more reliant on groundwater, leading to long-term depletion of these subterranean stores, which don't replenish like other reservoirs. Draining these precious aquifers accounts for a whopping 68 percent of all TWS loss in non-glaciated continental regions, the authors found.

A changing climate — also our doing — takes care of the rest. The decline in terrestrial water storage is being driven by high-latitude water losses in Canada and Russia "most likely due to ice and permafrost melt," the researchers said, and intense droughts in Central America and Europe.

All that missing water has to go somewhere — and it isn't back to land. While much attention is given to how melting ice sheets are raising sea levels, the authors found that, in reality, our ever-draining continents now contribute more freshwater to rising sea levels than the ice sheets do, while drying regions contribute more than land glaciers and ice caps.

There's a silver lining, they found: "While efforts to slow climate change may be sputtering, there is no reason why efforts to slow rates of continental drying should do the same." 

"Key management decisions and new policies," the authors add, especially regional and international efforts toward groundwater sustainability, "can help preserve this precious resource for generations to come. Simultaneously, such actions will slow rates of sea level rise."

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