Groundwater Monitoring
Over 75% of Earth permanently drier than 1990s, says UN
Dec 13 2024
In the last three decades, three-quarters of Earth’s land has become permanently drier, according to the office of the UN Convention to Combat Desertification (UNCCD).
Between 1990 and 2020, 77.6% of the planet’s land experienced drying conditions, with drylands expanding by an area (4.3mn km2) larger than India.
If this trend continues, up to five billion people could be living in drylands by 2100, facing water shortages and food security.
“For the first time, the aridity crisis has been documented with scientific clarity, revealing an existential threat affecting billions around the globe,” said UNCCD Executive Secretary, Ibrahim Thiaw.
How does climate change cause global drying?
As surface waters evaporate, communities drain aquifers that extremely dry soils prevent from recharging – thus, 40% of Earth is at a 22-year minimum in stored water.
Relatedly, the Clausius-Clapeyron relation dictates that warmer air holds more water vapor exponentially, producing more intense storms alongside deeper droughts.
In November 2024, NASA confirmed that global freshwater stores had been depleted by 290 cubic miles (or 2.5 times Lake Erie’s volume) annually since 2015.
“The drier climates now affecting vast lands across the globe will not return to how they were, and this change is redefining life on Earth,” says Thiaw.
Which regions are drying fastest?
Almost 96% of land in Europe, particularly Mediterranean and Southern Europe, experienced drying, a phenomenon inseparable from poor harvests.
South Sudan and Tanzania suffered the most extensive transition to drylands by percentage of land area, while China leads in total area.
All told, over a quarter (2.3bn) of humanity, live in transitioning regions, raising possibilities of mass exoduses and accompanying social instability.
Global drying raises famine risk
According to the report, aridity is the most significant driver in the degradation of agricultural systems – and it is currently impacting 40% of all arable land.
Drier regions experience more frequent and more intense dust storms, as demonstrated across the Middle East in recent years, removing critical topsoil, damaging crops and spreading pests.
By 2040, global yield is expected to be diminished by 20mn tons of maize, 21mn tons of wheat and 19mn tons of rice, with Kenya’s maize yield cut in half by 2050.
“Rising aridity will reshape the global landscape,” says Andrea Toreti, PhD, co-lead author of the report, “forcing societies to reimagine their relationship with land and water.”
READ: Famines, not heatwaves: how to think clearly about climate change
Drying regions heading for massive biodiversity loss
Species-richness is considered to decline in ecosystems that transition to drylands, depriving agriculture of vital services like pollination and soil stabilization.
In general, populations become separated as habitats fracture, limiting genetic diversity when it’s most needed to develop novel adaptations.
Whilst legacy species are on the back foot, invasive species meet little resistance, swiftly rendering these transitioning ecologies into monocultures.
Central Africa and eastern Asia, considered ‘biologically megadiverse’, will suffer most - but globally, over half (55%) of all species stand to lose their habitats.
Monitoring needed to aid adaptation to aridity
Integrating aridity metrics into drought monitoring systems allows early detection of changes and guides timely interventions. Tools like the Aridity Visual Information Tool equip policymakers with actionable data.
Sustainable land-use systems can mitigate aridity’s effects. Initiatives like the Great Green Wall demonstrate the potential of holistic land restoration efforts to combat desertification and support local economies.
Investing in water-efficient technologies, such as drip irrigation and rainwater harvesting, helps manage scarce resources. These solutions are essential for agriculture and water security in drying regions.
“The question is not whether we have the tools to respond,” says Nichole Barger, Chair of the UNCCD Science-Policy Interface. “It is whether we have the will to act.”
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