Climate Change Accelerates Dryland Expansion, Driven by Self-Propagating Mechanisms
(30-08-2024) Approximately 45% of the world’s land surface is now classified as drylands, including deserts, shrublands, grasslands, and savannah woodlands.
These arid regions are typically characterized by limited water availability, which significantly impacts both natural ecosystems and human-managed landscapes, including agriculture, forestry, and livestock production. Despite these harsh conditions, drylands are home to about 40% of the global population.
Drylands are primarily shaped by a combination of low precipitation and high atmospheric water demand. With climate change exacerbating these conditions, precipitation in drylands is declining while rising temperatures are increasing the atmosphere's demand for water. This leads to further water loss through evaporation, driving the global expansion of drylands and transforming once-humid regions into arid landscapes. While it has long been known that climate change and land management practices contribute to dryland expansion, a new study led by the Hydro-Climate Extremes Lab (H-CEL) at Ghent University in collaboration with Cardiff University, University of Bristol, and ETH Zurich has revealed a surprising factor: drylands themselves are accelerating their own spread.
In this groundbreaking study, H-CEL researchers quantified the process of dryland self-expansion by analyzing the sources of precipitation and heat over newly expanded drylands. By tracking air movements over these regions over the past 40 years, the team was able to calculate, for the first time, how much of the rainfall deficits and increased atmospheric water demand contributing to dryland expansion could be attributed to existing drylands. “Out of the approximately 5.2 million square kilometers of humid land that transitioned into dryland over the past four decades, more than 40% of the change was due to dryland self-expansion,” explains lead author Akash Koppa. The study found that drying soils in existing drylands release less moisture and more heat into the atmosphere, leading to reduced rainfall and increased atmospheric water demand in downwind humid regions. Over time, this process can cause these humid areas to gradually become drylands themselves.
In regions such as Australia and Eurasia, self-expansion has been identified as the primary driver of dryland spread. “As we continue to move towards a warmer and potentially drier future, the phenomenon of dryland self-propagation could accelerate, posing significant risks to human livelihoods, ecosystems, and socio-economic stability globally,” warns Koppa.
The study also highlights the regions’ most vulnerable to further dryland expansion and underscores the urgent need for climate change mitigation and sustainable land management practices. By quantifying the impact of distant vegetation responses on dryland expansion, the research emphasizes the importance of coordinated ecosystem conservation efforts in existing drylands. Supported by the European Union’s Horizon 2020 programme and the European Research Council (ERC), H-CEL and colleagues are currently focused on developing land-based adaptation strategies to prevent drought and heat propagation.
This groundbreaking research has been published in the prestigious journal Science, underscoring the critical importance of these findings within the global scientific community. The study’s detailed analysis and novel insights into the self-propagating mechanisms of dryland expansion, highlighting the urgent need for action in the face of accelerating climate change.
Contact
Dr. Akash Koppa
Professor Diego Miralles
Maarten De Coninck - Communications Manager
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