The findings could have significant impacts on climate change predictions as the ability of secondary forests to soak up carbon from the atmosphere may have been overestimated. By taking large amounts of carbon from the atmosphere, forests regrowing after clear-felling — commonly called secondary forests — have been thought an important tool in combatting human-caused climate change. However, the study by a group of Brazilian and British researchers shows that even after 60 years of regrowth, the studied secondary forests held only 40% of the carbon in forests that had not been disturbed by humans. If current trends continue, it will take well over a century for the forests to fully recover, meaning their ability to help fight climate change may have been vastly overestimated. Beyond helping fight climate change, secondary forests can also provide important habitats for threatened species. However, the researchers found that biodiversity levels in the secondary forests were only 56% of those seen in local undisturbed forests, with no increase in species diversity during the 20 years of monitoring. Many nations have made large reforestation pledges in recent years, and Brazil committed to restoring 12 million ha of forest under the Paris climate agreement. Taken together, these results suggest that these large forest restoration pledges need to be accompanied by firmer action against the deforestation of primary forests, and careful consideration about where and how to reforest. Biologist Joice Ferreira, a researcher at the Brazilian Agricultural Research Corporation, said: “Our study shows that in heavily deforested areas, forest recovery needs additional support and investment to overcome the lack of seed sources and seed-dispersing animals. This is different from other areas we have studied where historic deforestation is much lower and secondary forests recover much faster without any human intervention.”
