Drought is endemic to the American West along with heatwaves and intense wildfires. But scientists are only beginning to understand how the effects of multiple droughts can compound to affect forests differently than a single drought alone.
UC Santa Barbara forest ecologist Anna Trugman — along with her colleagues at the University of Utah, Stanford University and the U.S. Forest Service — investigated the effects of repeated, extreme droughts on various types of forests across the globe. They found that a variety of factors can increase and decrease a forest’s resilience to subsequent droughts. However, the study, published in Nature Climate Change, concluded that successive droughts are generally increasingly detrimental to forests, even when each drought was no more extreme than the initial one.
Droughts usually leave individual trees more vulnerable to subsequent droughts. “Compounding extreme events can be really stressful on forests and trees,” said Trugman, an assistant
University of Adelaide scientists have shown how droughts are threatening the health of wetlands globally.
Published in the journal Earth-Science Reviews, the scientists highlight the many physical and chemical changes occurring during droughts that lead to severe, and sometimes irreversible, drying of wetland soils.
“Wetlands around the world are incredibly important for maintaining our planet’s biodiversity and they store vast amounts of carbon that can help fight climate change,” says project leader Associate Professor Luke Mosley, from the University’s Environment Institute and School of Biological Sciences.
“Globally, wetlands cover an area greater than 12.1 million square kilometres and deliver at least A$37.8 trillion (Int$27 trillion) in benefits per year, such as for flood mitigation, food production, water quality improvement and carbon storage.”
Wetlands can suffer “water droughts” both from the effects of a drier climate, and also when excessive water is extracted or diverted that would normally flow into
Meteorologists track hurricanes over the oceans, forecasting where and when landfall might occur so residents can prepare for disaster before it strikes. What if they could do the same thing for droughts?
Stanford scientists have now shown that may be possible in some instances — the researchers have identified a new kind of “landfalling drought” that can potentially be predicted before it impacts people and ecosystems on land. They found that these droughts, which form over the ocean and then migrate landward, can cause larger and drier conditions than droughts that occur solely over the land. Of all the droughts affecting land areas worldwide from 1981 to 2018, roughly one in six were landfalling droughts, according to the study published Sept. 21 in Water Resources Research.
“We normally don’t think about droughts over the ocean — it may even sound counterintuitive. But just as over land, there can be times