A study led by the Swiss Federal Institute for Forest, Snow and Landscape Research (WSL) reveals a concerning rise in the frequency and intensity of long droughts over the past four decades. These prolonged dry spells have significant consequences for agriculture, energy production, and ecosystems worldwide. The research team, publishing their findings in Science, warns that the growing trend poses a serious threat to global environmental and economic stability.
Economic and Ecological Impact of Multi-Year Droughts
Multi-year droughts have become more frequent, prolonged, and extreme in recent years.
„Multi-year droughts cause enormous economic damage, for example in agriculture and power generation,“ says Dirk Karger from WSL, who led the study.
The extent of these droughts has grown by 50,000 km² annually, an area larger than Switzerland. This shift has had profound effects, particularly on ecosystems. Grasslands are especially vulnerable, with satellite images showing noticeable loss of green color. „In the event of extreme water shortages, trees in tropical and boreal regions can die, resulting in long-term damage to these ecosystems,“ warns Karger. Boreal vegetation, in particular, may take the longest to recover from such a climate disaster.
Tracking droughts through advanced meteorological data
Droughts typically become noticeable when they start damaging agriculture or forests. However, some regions, such as the tropical rainforest or the Andes, lack sufficient observational data. To address this, the research team from WSL and the Institute of Science and Technology Austria (ISTA) used meteorological data to analyze droughts by calculating anomalies in precipitation and evaporation from soil and plants (evapotranspiration) over the past 40 years. They created a drought index and observed vegetation changes during these drought events using global satellite data.
The role of climate change in increasing drought severity
Their method not only accurately modeled well-known droughts in regions like the western United States (2008-2014), Australia (2017-2019), and Mongolia (2000-2011), but also identified droughts in less accessible areas such as the Congo rainforest (2010-2018), where data is limited. The study ultimately produced a ranking of the most severe multi-year droughts over the past 40 years, analyzing precipitation and evaporation patterns as well as their impacts on vegetation.
Unsurprisingly, the rise in temperatures due to climate change plays a significant role in intensifying these droughts.
„The severity of perennial droughts will become more and more severe with climate change,“ says co-author Philipp Brun from WSL.
The study relies on CHELSA climate data prepared by Dirk Karger, which offers high-resolution climate information going back to 1979 across all continents. „Our drought inventory is the most comprehensive in the world for the last 40 years, at a resolution of five kilometers,“ says Liangzhi Chen, the study’s lead author. The data is publicly available to help countries better prepare for future multi-year droughts.
Original publication: science.org/doi/10.1126/science.ado4245
