Study says potential for natural regrowth to absorb carbon has been substantially underestimated
A cleared area of forest in the Amazon basin in Brazil. Photograph: Carl de Souza/AFP/Getty Images
Fiona Harvey Environment correspondent
Wed 23 Sep 2020 17.53 BST
The costly and difficult work of replanting forests that have been cut down may not be the only way to restore the Earth’s carbon-absorbing capacities, research has found, as allowing trees to grow back naturally without intervention could offer a cheaper alternative.
Keeping forests standing is still a better way to reduce the impact of the climate crisis, but in large areas of the world, forest and scrubland has already been cleared or degraded in some way, through deforestation, failed agriculture or some other exploitation. Often, the loggers, prospectors and ranchers quickly move on, leaving devastation in their wake.
Conventional thinking has been that replanting was the best way to restore the carbon balance, but a study published in the journal Nature shows that leaving forests to regrow naturally is cheaper and also allows native trees and wildlife to flourish.Advertisement
Susan Cook-Patton, of the Nature Conservancy, lead author of the study, said natural regrowth was usually a simple option. “One would need to remove any disturbance or land use that prevented the forest from coming back – for example, if the land is grazed one might remove the cows or put up a fence,” she told the Guardian. “But otherwise the forest is allowed to return without active planting.”
The study did not compare the rates of regrowth when land is left alone with the rates when there is intervention, or the costs of targeted intervention. Such intervention might be needed to help forests regrow to their maximum biodiversity, said Cook-Patton.
“If seed sources are nearby and the site isn’t too degraded, then diverse forests can likely grow back by themselves,” she said. “If the site is degraded and seed sources are far away, or if the only seed sources are from one or a few species, one might want to actively plant the whole site, or do some patch planting to foster recovery of a more diverse forest. Active planting doesn’t necessarily ensure a more diverse forest in the end, since often it can be hard to acquire diverse seedlings to plant.”
Standing forests absorb about a third of the greenhouse gas emissions emitted by human activities each year. The study found that the potential for natural regrowth to absorb carbon had been substantially underestimated, by about a third overall and by about a half in the case of tropical forests.
The paper provides a means of mapping where in the world natural forest regrowth is likely to be a good option.
“We know there is no single, one-size-fits-all solution for addressing climate change,” said Nancy Harris, of the World Resources Institute, co-author of the study. “Our goal was to show where forests can capture carbon fastest on their own, a mitigation strategy that complements keeping forests standing. If we let them, forests can do some of our climate mitigation work for us.”
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