What happens to cleared rainforest areas when they are left back to nature? Researchers observed this in a nature reserve in Ecuador. The results give cause for hope: new trees are rapidly growing on former pastures and cocoa plantations and many animal species that previously disappeared are also returning. After 30 years, around 90 percent of the former biodiversity had been restored. However, an important prerequisite is that there are still enough forests in the area that can spread again.
Tropical rainforests are home to almost two-thirds of all vertebrate species and three-quarters of all tree species. They are the most diverse terrestrial ecosystem on earth. However, around 60 percent of these diverse rainforests have already been lost or severely damaged by human activities. The forest area continues to decline drastically, primarily due to clearing for agriculture. At the same time, nature conservation organizations are trying to buy up areas and give them back to nature. But how promising are such measures?
Back to nature
A team led by Timo Metz from the Technical University of Darmstadt looked into this question. To do this, the researchers analyzed the condition of the rainforest on 62 areas in the Chocó region in northwest Ecuador. Here, the local nature conservation organization Jocotoco has been committed to protecting the rainforest for several decades and has integrated numerous former agricultural areas into a large nature reserve. The areas included in the study included actively used pastures and cocoa plantations, untouched virgin forests and newly grown forests of varying ages on areas that were previously used as pastures or cocoa plantations.
The result: As soon as land use was stopped, the first seedlings of rainforest trees soon sprouted on the former agricultural land. Many animal species also resettled. Within 30 years, three-quarters of the animal and plant species typical of pristine tropical rainforests had returned, and biodiversity had regenerated to around 90 percent of original levels. “Rainforests as a complex ecosystem and species-rich community show amazing resilience and the ability to return to their original state,” says Metz. “This stability has often been modeled theoretically, but has not yet been shown on the basis of such extensive, empirical data.”
Animals as helpers
The research team found that areas that had previously served as cocoa plantations recovered more quickly than former pasture areas. There were already shade trees there that limited the growth of grass and created the basis for renewed forest cover. Animals also play an important role in renaturation: “The many quickly returning animal species not only benefit from forest regeneration, but are also its most important actors,” explains Metz’s colleague Nico Blüthgen. “Bats, monkeys and other mammals as well as birds bring the tree seeds back into the cleared areas, dung beetles dig the seeds into the ground, and hundreds of other animal species ensure pollination.”
From the perspective of Jocotoco leader Martin Schaefer, the results are confirmation of the work of his organization. “The realization that 90 percent of biodiversity returns within a human generation on its own shows how effectively we can protect nature,” he says. “By purchasing and protecting land, we can preserve the diversity of life and the foundations of our societies – soil, water and the pollination of plants that form our food base.”
However, according to the researchers, an important prerequisite for this natural regeneration is that there are still enough forests in the area from which plant seeds and animals can spread again. This is also why the protection of intact ecosystems is particularly important. “The deforestation rate of tropical forests is currently much higher than their protective measures,” says Blüthgen. “Four to six million hectares are lost worldwide every year. These annual losses are almost as high as the area of all long-term renaturation measures combined.”
Source: Timo Metz (Technical University of Darmstadt) et al., Nature, doi: 10.1038/s41586-026-10365-2