The astonishing resilience of a tropical rainforest

Tropical rainforests are home to almost two-thirds of all vertebrate species and three-quarters of all tree species. They are the most species-rich terrestrial ecosystem on Earth. However, more than half of these diverse rainforests have already been cleared, and their area continues to decline drastically, primarily for agricultural purposes.

Is there a chance of regeneration, and can not only trees but also the unique diversity of animal species return to cleared areas? These questions were addressed by the ‘Reassembly’ research group led by the Technical University of Darmstadt in Germany. The findings have now been published in the journal Nature.

The answer is surprisingly clear and encouragingly positive. Trees grow back quickly on agricultural land as soon as land use ceases. Also, a wide variety of animal species return. Biodiversity recovered to more than 90 per cent of its original level within 30 years, the study reveals. During this period, as many as three-quarters of the animal and plant species typical of primary forest reappeared. This applies at least to the study area in the region Chocó in north-western Ecuador, an area where few primary forests and larger secondary forests remain. These form the reservoir for many returning animal and plant species.

Researchers from more than 30 universities and institutions have, for the first time, conducted a detailed study of the natural regeneration of 16 different groups of organisms (animal, plant and bacterial species) along a regeneration gradient. A total of 62 sites were compared. For several decades these sites  have been protected by the Ecuadorian conservation organisation Jocotoco and integrated into a large nature reserve comprising actively used pastures and cacao plantations, secondary forests of varying ages that were formerly used as pastures and plantations, and untouched primary forests.

Ability to return to their original state

“As complex ecosystems and species-rich communities, rainforests demonstrate remarkable resilience and the ability to return to their original state,” explains lead author Timo Metz, who carried out and summarised the extensive analyses as part of his PhD at TU Darmstadt. “This stability has often been modelled theoretically, but until now it has not been demonstrated on the basis of such extensive empirical data.”

Senior author Nico Blüthgen, Professor of Ecology at TU Darmstadt and spokesperson for the ‘Reassembly’ research group, adds: “The many animal species that return quickly are not only beneficiaries of forest regeneration, but are also its key agents. Bats, monkeys and other mammals, as well as birds, return tree seeds to the cleared areas. Dung beetles bury the seeds in the soil. And hundreds of other animal species ensure pollination.”

Jocotoco Director Martin Schaefer, who initiated the study together with Blüthgen, emphasises: “Our findings that 75 per cent of species composition and 90 per cent of species diversity can recover within a single human generation through our own efforts show just how effectively we can protect nature.

A total of 41 researchers, mainly from Germany and Ecuador, contributed to this unprecedented study of more than 8,500 species. Previous studies in Central and South America have well documented that the original diversity and biomass of trees require more than 100 years to fully regenerate. For most animal species, however, it was largely unknown whether and how quickly they could recover.

Nature can recover effectively when protected

The new study revealed clear differences between species groups. While some mobile animal groups regenerated within just a few years, communities of invertebrates in the leaf litter or bacteria in the soil take much longer than tree species. A comparison of pastures and cacao plantations revealed shorter regeneration times for the latter. Thanks to plantation trees left on site that provide shade and foliage in the early stages rather than highly competitive pasture grasses, plantations may represent a starting advantage for many organisms.

Efforts to restore ecosystems are underway all over the world. The latest study provides compelling evidence of how quickly and effectively nature recovers when protected. Blüthgen, however, stresses the importance of conserving intact ecosystems as well: “The rate of deforestation in tropical forests is currently much higher than the rate of conservation measures – every year, four to six million hectares are lost world-wide. These annual losses are almost as high as the total area covered by all long-term restoration measures combined.”

(TU-Darmstadt/wi)

Reference:

Metz, Timo et al.: Biodiversity resilience in a tropical rainforest, in: „Nature”, 652/2026DOI: 10.1038/s41586-026-10365-2

More information:

Link to Reassembly research group