Eddie Gonzales Jr. – MessageToEagle.com – Persistent multi-year droughts, increasingly common since 1980, will intensify with climate warming, warns a new study.
The Yeso reservoir in central Chile during a megadrought peak in Summer 2020. © Image credit: Vicente Melo Velasco | ISTA
This 40-year global quantitative inventory, published in Science, informs policy on human-induced climate change and identifies previously overlooked events.
Over the past fifteen years, Chile has faced a severe megadrought, the longest in a millennium, depleting water reserves and impacting its mining sector. This illustrates how climate change causes prolonged droughts and water shortages globally.
However, droughts tend only to be noticed when they damage agriculture or visibly affect forests. Thus, some pressing questions arise:
Can we consistently identify extreme multi-year droughts and examine their impacts on ecosystems? And what can we learn from the drought patterns of the past forty years?
To answer these questions, researchers have analyzed global meteorological data and modeled droughts between 1980 and 2018. They demonstrated a worrying increase in multi-year droughts that became longer, more frequent, and more extreme, covering more land.
“Each year since 1980, drought-stricken areas have spread by an additional fifty thousand square kilometers on average—that’s roughly the area of Slovakia, or the US states of Vermont and New Hampshire put together— causing enormous damage to ecosystems, agriculture, and energy production,” says ISTA Professor Francesca Pellicciotti, the Principal Investigator of the WSL-funded EMERGE Project, under which the present study was conducted.
The Yeso region in Central Chile, visibly dry during a peak of the megadrought in the Summer of 2020. © Vicente Melo Velasco/ISTA
The team aims to unveil the possible long-lasting effects of persistent droughts around the globe and help inform policy preparing for more frequent and severe future megadroughts.
They used the CHELSA climate data prepared by WSL Senior Researcher and study author Dirk Karger, which goes back to 1979.
They calculated anomalies in rainfall and evapotranspiration—water evaporation from soil and plants—and their impact on natural ecosystems worldwide. This allowed them to determine the occurrence of multi-year droughts both in well-studied and less accessible regions of the planet, especially in areas like tropical forests and the Andes, where little observational data is available.
“Our method not only mapped well-documented droughts but also shed light on extreme droughts that flew under the radar, such as the one that affected the Congo rainforest from 2010 to 2018,” says Karger. This discrepancy is likely due to how forests in various climate regions respond to drought episodes. “While temperate grasslands have been most affected in the past forty years, boreal and tropical forests appeared to withstand drought more effectively and even displayed paradoxical effects during the onset of drought.”
But how long can these forests resist the harsh blow of climate change?
Rising temperatures, prolonged droughts, and high evapotranspiration rates lead to drier ecosystems despite intense rainfall. Scientists use satellite imagery to monitor drought impacts by observing changes in vegetation greenness. This method is effective in temperate grasslands but challenging for dense tropical forests, leading to an underestimation of effects there.
Chile, 2017. The Upper Rio Yeso catchment: a tributary to the Maipo River which serves the Chilean capital, Santiago. © Thomas Shaw/ISTA
The team’s analysis found megadroughts have the greatest impact on temperate grasslands. ‘Hotspot’ regions include the western USA, central and eastern Mongolia, and southeastern Australia, overlapping with two documented multi-year ecological droughts.
The team noted that tropical forests can offset drought effects if they have sufficient water reserves. Boreal forests (and tundra) on the other hand, respond differently. The warming climate extends the boreal growth season because vegetation there is limited by low temperatures, not water scarcity.
The results indicate a clear trend of intensifying megadroughts. The team created the first consistent global picture of megadroughts and their impact on vegetation at high resolution. The long-term effects on the planet and ecosystems remain largely unknown, but data already aligns with observed Arctic greening.
“But in the event of long-term extreme water shortages, trees in tropical and boreal regions can die, leading to long-lasting damage to these ecosystems. Especially, the boreal vegetation will likely take the longest to recover from such a climate disaster,” says Karger.
Researchewrs believe that their results will help change our perception of droughts and how to prepare for them.
Written by Eddie Gonzales Jr. – MessageToEagle.com Staff Writer