Climate change transforming forests worldwide, leading to increase in shorter and younger trees: Study
This trend is likely to continue with climate warming. A future planet with fewer large, old forests will be very different than what we have grown accustomed to, says an expert
Earth's towering forests may soon become a thing of the past. A new study claims that climate change is leading to the rise of shorter and younger trees. These changes could spell trouble for the future, say researchers. Since the 1900s, we have lost a third of the old-growth forests, home to older trees. They capture carbon dioxide -- a gas that warms the planet -- and shelter wildlife. Younger and smaller trees also perform the same functions, but pale in comparison, says the study.
"This trend is likely to continue with climate warming. A future planet with fewer large, old forests will be very different than what we have grown accustomed to. Older forests often host much higher biodiversity than young forests and they store more carbon than young forests," says Dr Nate McDowell, an Earth Scientist at the US Department of Energy's Pacific Northwest National Laboratory and the study's lead author.
Older trees are increasingly getting wiped out. "This is likely to have big implications for the services those forests provide, such as mitigating climate change. Increasing rates of tree mortality driven by climate and land-use change, combined with uncertainty in the mix of species that will form the next generation, pose big challenges for conservationists and forest managers alike," says Dr Tom Pugh from Birmingham Institute of Forest Research. The researchers made these observations after reviewing data on more than 160 previous studies about tree mortality and its global causes. They used satellite imaging to analyze data on land-use change.
What is driving tree mortality?
Rising temperatures, droughts, wildfire, insect outbreaks, and wood harvests are contributing to the fall of older forests. Such events could rise in the coming days. As a result, McDowell predicts that shorter trees will continue to inhabit the planet in the future. Warming temperatures limit growth, leading to shorter trees and even mortality. Droughts also contribute to the loss of trees and indirectly make forests susceptible to insect outbreaks. According to the study, such events are on the rise. Fungi and bacteria and vines are choking trees to death. Wildfires lead to slower plant growth.
“It’s not a shock but it’s very sad,” Kristina Anderson-Teixeira, an ecologist and leader of the ForestGEO Ecosystems & Climate Program at the Smithsonian Conservation Biology Institute and a co-author of the study, tells NPR. “We as a human society are hitting these forests so rapidly with so many different changes that they can’t keep up.” Rising carbon dioxide levels boost tree growth. But without enough reserves of water and nutrients, forests cannot benefit from the gas. “For a long time, scientists have predicted that elevated carbon dioxide and warming will increase carbon storage in forests that will help to offset climate change. But this study adds to a growing concern that these factors, along with human disturbance, may, in fact, be decreasing the amount of carbon stored in these ecosystems," Prof Tom Crowther, at ETH Zurich University in Switzerland and not part of the analysis team, tells Guardian.
"I would recommend that people try to visit places with big trees now, while they can, with their kids. Because there's some significant threat, that might not be possible sometime in the future," McDowell says.