Revealed: The unexpected factor leading to an increase in sea levels - it's the land, not the ice.
In a concerning development, dry areas around the globe are expanding at an alarming rate, with mega-dry zones merging into vast, connected regions. According to a study published in Science Advances, these mega-dry zones are spreading by an area twice the size of California every year.
The study, which tracked how water is being stored across Earth's land surface, including groundwater aquifers, using satellite observations, reveals that human activity significantly contributes to this expansion. Deforestation, land use changes, and greenhouse gas emissions that exacerbate climate change are accelerating landscape drying, leading to unprecedented continental drying and the merging of previously isolated dry hotspots into vast “mega-drying” regions.
This continental drying not only reduces freshwater availability, intensifying global water shortages, but also contributes to sea level rise beyond the effect of melting glaciers. As landscapes dry out, groundwater and soil moisture are depleted and eventually lost to the atmosphere or surface runoff, mobilizing water that would otherwise remain stored on land into the oceans. This land-to-ocean water transfer has been found to contribute more to sea level rise than glacier melt itself.
Human-induced hotter and drier conditions also increase the prevalence and severity of forest fires, which further degrade vegetation cover and soil moisture retention, intensifying drying trends and carbon emissions. This feedback loop worsens water scarcity and influences regional climate patterns.
The study also highlights the depletion of groundwater reserves, particularly in regions like California, where it is being used at an increasing rate. In many places, the study states that the depleted groundwater will not be replenished on human timescales. This overuse of groundwater undermines regional and global water and food security, a problem that is not fully acknowledged around the world.
The study underscores the importance of protecting the world's groundwater supply, particularly in continents that are drying, in a warming world. Key decisions, both at national and international levels, are urgently needed to preserve this vital resource for future generations.
One such 'mega-dry' zone stretches from the southwest coast of the US down into Mexico. The depletion of groundwater reserves in the Central Valley of California and the Colorado River basin has led to the merging of dry areas with those in Central America.
This research serves as a stark reminder of the urgent need to address our impact on the planet's water resources. By taking steps to reduce greenhouse gas emissions, conserve water, and manage land use sustainably, we can help mitigate the expansion of mega-dry zones and ensure a more secure future for our planet and its inhabitants.
- The continental drying, as revealed by the study published in Science Advances, is not only linked to climate change but also contributes to sea level rise, surpassing the effect of melting glaciers.
- Human-induced activities, such as deforestation, land use changes, and increased greenhouse gas emissions, are significantly contributing to the expansion of mega-dry zones across the Earth's land surface.
- The depletion of groundwater reserves, like those in California, is a critical issue as the depleted groundwater will not be replenished on human timescales, compromising regional and global water and food security.
- In light of the stark findings from this research, it's crucial for key decisions to be made at both national and international levels to protect the world's groundwater supply, particularly in continents experiencing significant drying and warming.
