Globally, freshwater reserves are diminishing, with recent analyses indicating that a substantial portion is now flowing into the oceans. This phenomenon means that terrestrial landmasses, characterized by their drying landscapes, are contributing more to the concerning escalation of global sea levels than the diminishing ice sheets.
A scientific cohort, spearheaded by Earth system specialist Hrishikesh Chandanpurkar from FLAME University in India, has posited that prompt interventions are imperative to fortify ourselves against considerably more arid conditions in the future. These foreseen aridities are a consequence of the ongoing climate change phenomenon and the excessive extraction of groundwater by human activities.
By leveraging more than twenty years of orbital observational data from the Gravity Recovery and Climate Experiment (GRACE) and its successor mission, both operated by NASA, the investigators have meticulously constructed a comprehensive depiction of alterations in terrestrial water storage since 2002, elucidating the causative factors.
“Our findings reveal that continental landmasses, encompassing all land surfaces apart from Greenland and Antarctica, are experiencing desiccation at unprecedented velocities. Furthermore, the geographical extent of these drying continental areas is expanding annually by an area approximately equivalent to twice the size of the state of California,” the researchers articulate in their publication.
Human endeavors have significantly perturbed the Earth’s hydrological cycle through the emission of greenhouse gases, which fundamentally alter atmospheric conditions, and by rerouting watercourses and natural precipitation collection zones. While certain regions have become measurably wetter and others demonstrably drier, these climatic shifts exhibit an asynchronous progression.
“The phenomenon of aridification in previously dry regions is proceeding at a more accelerated pace than the humidification observed in wetter zones,” the research group asserts. “Concurrently, the geographical domain experiencing a reduction in water presence has enlarged, whereas the territory witnessing an increase in moisture content has contracted.”
This collective trend signifies a net diminution of terrestrial water reserves, precipitating profound global repercussions. This encompasses not only surface freshwater bodies, such as lakes and rivers, but also the subterranean groundwater concealed within geological aquifers. A significant majority of the global populace, specifically 75 percent, resides within the 101 nations currently experiencing escalating rates of freshwater depletion.
The destination for this lost freshwater is predominantly the ocean. The volume of freshwater displaced from continental landmasses is now substantial enough to contribute more significantly to the rise in sea levels than the melting of polar ice caps.
This overarching trend of continental desiccation is largely attributable to water loss observed in high-latitude territories, including Canada and Russia. These regions, not typically perceived as arid, are experiencing this phenomenon, which the authors hypothesize is linked to the thawing of ice and permafrost within these locales.
In continental areas devoid of glaciers, a considerable 68 percent of the terrestrial water supply depletion can be ascribed to human-induced groundwater extraction. Moreover, recent and exceptionally severe droughts experienced in Central America and Europe have exacerbated this situation; these climatic events are predicted to intensify in frequency and severity as the climate crisis progresses.
As our ever-increasing emissions of fossil fuels irrevocably alter the precipitation patterns upon which we have historically depended, populations are increasingly turning to groundwater reserves out of necessity. This surge in demand places additional strain on these vital water sources, which are not being naturally replenished at a rate commensurate with their extraction.
On numerous continents, the excessive reliance on groundwater for irrigation in arid agricultural zones is a primary driver of depletion. Illustrative examples include California’s Central Valley, which is responsible for cultivating 70 percent of the world’s almonds, and the cotton cultivation adjacent to the now-arid Aral Sea basin in Central Asia, a region that has experienced complete desiccation.
“Currently, the overexploitation of groundwater represents the most significant contributor to the decline in terrestrial water storage within drying regions. This anthropogenic pressure substantially exacerbates the repercussions of rising global temperatures, increasing aridification, and the occurrence of extreme drought events,” the authors report.
“Safeguarding the world’s groundwater resources is of paramount importance in a warming climate and across continental landmasses that are now demonstrably experiencing desiccation.”
The researchers express optimism that collaborative efforts at regional, national, and international levels, focused on instituting sustainable groundwater management practices, will serve to conserve this invaluable resource for future generations.
“While progress in mitigating climate change may be faltering, there is no inherent impediment to ensuring that initiatives aimed at decelerating the rates of continental drying do not suffer a similar fate,” the research team concludes.
