Our Forests Can’t Handle This Much Stress

A heatwave killed more than 1,000 people in Spain and Portugal last week, with temperatures eclipsing 110 degrees Fahrenheit in some parts of the country. Meanwhile, wildfires are surging across the European continent. While over 1,200 firefighters battled blazes in France's southwestern region of Gironde, at least 28,000 residents were evacuated. The extreme heat is now hitting the United Kingdom, where temperatures are expected to hit record highs this week, prompting museum closures and cut backs in public transit service.

Climate change may be making European forests, among many others around the world, less resilient to these increasingly common extreme events, a new study suggests.

If forests can’t recover quickly after disasters, their ability to mitigate climate change may also decline, potentially spurning even more dangers to forests. Trees play a crucial role in balancing the impact humans have on the planet, sucking up about a third of the carbon emissions, according to the study.

The researchers measured the change in forest resilience around the world between 2000 and 2020 by applying machine learning to satellite data tracking vegetation, writes Adam Vaughan for New Scientist. Arid, tropical and temperate forests, which make up most of the world’s forests, are not bouncing back as strongly as they used to. Boreal forests, which contain coniferous trees and are found in northern parts of the globe, such as Canada and Russia, actually grew more resilient on average.

Deforestation and logging affect the health of forests, but droughts and extreme weather, like those facing Europe right now, are becoming more common and more severe. The researchers also examined whether human management was at fault, but as reported by Chelsea Harvey in E&E News, forests both managed and not managed by humans are struggling to adapt.

Giovanni Forzieri of the University of Florence in Italy, who led the study, told New Scientist their model looked at the effect of different environmental factors on resilience, and found that variation in climate had the biggest negative impact. They measured resilience by the forest’s quality as a forest and not becoming a grassland like savannah, reports New Scientist, as well its ability to withstand pest infestations. For boreal forests, some of which showed signs of increased resilience, the benefits of warmer temperatures and increased levels of carbon dioxide may outweigh the harms of climate change, reports E&E News. The results were published last week in the journal Nature.

Martin Sullivan, a statistical ecologist at Manchester Metropolitan University who was not involved in the study, told New Scientist that satellite data only provide a narrow window to measure change. “While 20 years of data mean changes can start to be assessed, it is still quite a short timeframe for detecting shifts [in resilience],” he said.

According to E&E News, some studies suggest that forests can experience so much distress that they stop recovering, passing a tipping point after which they only continue to shift into grassland. Scientists aren’t exactly sure how much damage is too much, but the new study estimates that almost a quarter of forests have passed their tipping point and are continuing to lose resilience.

Will Sullivan | | READ MORE

Will Sullivan is a science writer based in Washington, D.C. His work has appeared in Inside Science and NOVA Next.