Climate change may increase frequency and severity of droughts
Zhang Yu/VCG via Getty Images
Severe droughts that last for years have become hotter, drier, and larger since the 1980s. These long-lasting droughts – some of which are so severe that they can be classified as “megadroughts” – can be particularly devastating to agriculture and ecosystems.
Rising temperatures associated with climate change have increased the risk of drought because warmer air can hold more moisture, leading to increased evaporation from the land. Combined with changing precipitation patterns, which result in less rain, this could increase and prolong drought periods – as seen in the recent megadrought in parts of North and South America, the worst in a millennium.
Dirk Karger He and colleagues at the Swiss Federal Institute for Forest, Snow and Landscape Research identified more than 13,000 droughts lasting at least two years between 1980 and 2018 to reveal long-term trends. They found that, since the 1980s, the most severe multi-year droughts have become even drier and warmer.
Drought has also affected a large part of the world, with the area affected by the 500 most severe drought events in any given year expanding by about 50,000 square kilometers annually. “This is an area bigger than Switzerland,” says Karger.
Satellite images of greenery in drought-affected areas have also shown that some ecosystems have turned brown, indicating that dry conditions are having an impact. The most dramatic change was in temperate grasslands, which are more sensitive to changes in water availability, while tropical and boreal forests showed less response.
The researchers did not conduct a formal analysis to define how much human-caused climate change has contributed to this trend, but the patterns are consistent with what researchers expect with rising temperatures, say benjamin cook at Columbia University in New York, who was not involved in the research.
Cook says this work highlights that the consequences of long-term drought can be as severe as climate disasters like devastating wildfires or powerful hurricanes. “For both people and ecosystems, the cumulative impact of drought really matters.”
Subject:
