Can a tropical forest mend itself? After trees are cut down and wildlife flees, do microbes on the dank, leafy floor and woody giants with epiphyte-laden crowns come back; do the pollinators, seed dispersers and entangled webs of predator and prey return? And how, exactly, does it happen?

A new ambitious research project is trying to find out. Based out of the 15,000-hectare (37,000 acre) Canandé Reserve in Ecuador’s Chocó Forest, the aptly named Reassembly Research Unit is documenting how the forest recovers after clearing. The results, by a joint German and Ecuadorian team, so far indicate that many species assemblages return within a few decades, though the full forest community, including mature trees, takes longer to reestablish. These answers shed light on intricate ecosystem processes. They are also of immense conservation value, potentially in the tropics worldwide.

“Unfortunately, most of the tropical forests are becoming secondary forest, especially in this part of the tropics,” says María-José Endara, a researcher with Reassembly and evolutionary ecologist at the University of the Americas in Quito. “If we want to keep having a forest, then we have to be prepared to let this forest regenerate. And we need the knowledge and the understanding of how this process will go.”

Ecuador’s Chocó

The Chocó ecoregion is astounding, one of the 10 most biodiverse spots on Earth. Lying west of the Andes, it stretches through Panama, Colombia and Ecuador, covering a huge elevation range. A quarter of its plants are found nowhere else on the planet, and the Ecuadorian Chocó alone is home to more than 900 bird species, as well as iconic mammals like jaguar, ocelots and more.

But like other tropical forests, the Chocó is under immense pressure. In Ecuador, less than 60% of the Chocó Forest remains, according to analysis by the Monitoring of the Andean Amazon Project (MAAP), with deforestation most severe in the lowlands. Portions of the remaining forest are protected in national parks, private reserves and Indigenous territories, including the nonprofit Jocotoco Foundation’s Canandé Reserve, where the Reassembly project is based.

For most of the drive to the reserve from the capital Quito, unending monocultures flank the road, says Nico Blüthgen, head researcher at Reassembly and ecology professor at the Technical University of Darmstadt in Germany. But eventually you take a ferry across a river and everything changes, he says.

“Then you’re in paradise,” Blüthgen says. “Everybody’s breathing [again].”

Still, not all of the forest is not as pristine as it might at first appear to an untrained eye. At various times, farmers cleared patches of the forest for small-scale cattle ranching or cacao cultivation. Now, interspersed among the old-growth forests are patches of secondary forest, many of them very well developed with large trees.

This presented a unique opportunity. The Jocotoco Foundation’s meticulous recordkeeping and close relationship with the community meant the researchers knew the history of the forest and could figure out the age of these secondary forest stands. Trekking up and down hillslopes and wading through streams, team members established 62 monitoring plots in Canandé and the adjacent Tesoro Escondido Reserve. Taken together, these plots make up a chronosequence — a snapshot of the forest ecosystem over several decades of recovery — as well as old growth.

Tropical forests are more than just trees. Plants, animals, insects, fungi and myriad other organisms are intricately connected through complex webs and relationships, Blüthgen says. By meticulously sampling biodiversity in each plot, and conducting experiments, the researchers are figuring out how the ecosystem responds to disturbance. That includes how quickly and in what order different species return, and how that feeds into further forest recovery.

Researchers are tracking this recovery for more than 10,000 species. Many are insects identified only by DNA, but there’s also a broad range of taxa.

“Birds, bats, beetles, bees, you name it, it’s all there,” Blüthgen says.

Since the project began about four years ago, the team has already published nearly two dozen peer-reviewed journal articles. A January 2025 study found that former cacao farms and pastures supported different bird communities as they recovered. A December 2024 study described the recovery of ground birds and mammals like ocelots, and found their diversity and biomass in secondary forests was similar to those in old-growth forests after just 20 years. Numerous other publications are in preparation.

“We were now, for the first time, showing that this broad spectrum of different taxon recovers at different speeds,” Blüthgen says. “We see some are earlier, some are later, but they all show a tendency to recover.”

The findings so far align with previous research showing that tropical forests have a remarkable capacity for recovery. For example, a 2021 Science study of tropical forest sites in the Americas and West Africa found that cleared forest recovered nearly 80% of old-growth values in 20 years, though full recovery took more than a century.

One thing that’s new about the Reassembly project is the focus on such a broad range of taxa, says Robin Chazdon, an adviser and collaborator to the project, and professor at the Forest Research Institute at Australia’s University of the Sunshine Coast. Chazdon, who was a co-author on the 2021 Science study, says most similar studies only look at a few groups, like trees, plants or birds.

Also unique is the inclusion of former cacao plantations and cattle pastures. Chazdon says she’s not aware of any other studies that compare forest recovery from these two common modes of deforestation in such detail.

Many researchers now argue that, under certain conditions, allowing tropical forests to regenerate naturally or with limited strategic interventions is the most cost-effective way to repair deforested areas. Across the tropics, 215 million hectares (531 million acres) of deforested land, an area about the size of Greenland, could be naturally regenerated, according to a 2024 Nature study on which Chazdon was a co-author.

Research on forest regeneration, like the Reassembly project, helps scientists figure out if and when interventions are useful.

“If we need to do tree planting to bring about restoration, it’s always better to do that informed by what the natural process is,” Chazdon says. “For example, there’s now been quite a bit of research looking at whether we need to plant trees uniformly over an area, or whether we could plant islands or clusters of trees and save money and be just as effective.”

The Jocotoco Foundation has engaged in active restoration in parts of Canandé, particularly in the upper elevations. But for the most part, it has simply protected the forest and let it come back on its own. In all, it has actively restored 50 hectares (124 acres), while leaving 2,000 hectares (nearly 5,000 acres) to regenerate naturally. In some of the other reserves that the foundation manages in southern Ecuador, where the land was more degraded and patches of deforestation were larger, it has taken a more hands-on approach with tree planting.

Reassembly is, essentially, a fundamental research unit; it’s not trying to come up with the fastest way to grow trees, Blüthgen says. But the research helps put biodiversity and carbon values on naturally regenerated secondary forests. Those types of hard numbers are important to attract funding through carbon credits, and can legitimize natural regeneration as an alternative to reforestation.

The project is also giving Ecuadorian scientists and students more field research opportunities.

“One thing that was really nice about the German crew is that they were actually looking for Ecuadorian researchers that will actively collaborate,” Endara says.

A sophisticated lab, built in 2022 and largely funded by an anonymous donor, means researchers can do longer field stints and perform analyses with specialized equipment on site. That’s leading to new discoveries in the understudied Choco Forest. For example, the team discovered two new-to-science species of worm-like amphibians, one more than 80 centimeters (31 inches) long, and used DNA analysis to reveal the remarkable specializations of dung beetles.

“There’s always so many phenomena that we discover, that get lost in the statistical details,” Blüthgen says. “Every time you go there, there’s so many new things that you haven’t seen before.”

That sense of wonder is tempered by an awareness of just how vulnerable this and other tropical forests have become.

When Blüthgen first visited the study site in the Chocó, he was amazed at how fast the forest could recover. But that only happens if there’s enough mature forest nearby to act as a source of seeds, insects, birds, mammals, microbes and more.

“It’s a story of opportunity and hope, if you want, right?” he says. “This recovery of forest does work in such a context … but it’s not a relief. Why do we destroy it in the first place?”

Banner image: A masked Tree Frog (Smilisca phaeota) in the Ecuadorian Choco. Image by Nico Bluthgen.

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Citations:

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Grella, N., Pedersen, K., Blüthgen, N., Busse, A., Donoso, D. A., Falconí‐López, A., … Müller, J. (2025). Vertebrate diversity and biomass along a recovery gradient in a lowland tropical forest. Biotropica, 57(1), e13417. doi:10.1111/btp.13417

Poorter, L., Craven, D., Jakovac, C. C., Van Der Sande, M. T., Amissah, L., Bongers, F., … Hérault, B. (2021). Multidimensional tropical forest recovery. Science, 374(6573), 1370-1376. doi:
10.1126/science.abh3629

Williams, B. A., Beyer, H. L., Fagan, M. E., Chazdon, R. L., Schmoeller, M., Sprenkle-Hyppolite, S., … Crouzeilles, R. (2024). Global potential for natural regeneration in deforested tropical regions. Nature, 636, 131-137. doi:10.1038/s41586-024-08106-4

Bock, S., Arroba-López, T. E., Velez-Giler, H. L., Moreira, V., Wiedebusch, M. L., Neira-Salamea, K., … Ron, S. R. (2024). Two new species of Caecilia (Gymnophiona: Caeciliidae) from the Ecuadorian humid Chocó. Salamandra, 60(4), 209-236. Retrieved from https://salamandra-journal.com/index.php/contents/2024-vol-60/2158-bock,-s-,-t-e-arroba-lópez,-h-l-velez-giler,-v-moreira,-m-l-m-wiedebusch,-k-neira-salamea,-m-wilkinson,-n-fuchs,-m-schönleitner,-m-o-rödel-s-r-ron

Pedersen, K. M., von Beeren, C., Oggioni, A., & Blüthgen, N. (2024). Mammal dung–dung beetle trophic networks: An improved method based on gut-content DNA. PeerJ, 12, e16627. doi:10.7717/peerj.16627

Griesbaum, F., Lindner, T., Bock, S., Ernst, M., Neira-Salamea, K., Moreira, V., … Rödel, M. O. (2023). Nine predation events by snakes from the Chocó rainforest of Ecuador. Herpetology Notes, 16, 749-756. Retrieved from https://www.biotaxa.org/hn/article/view/82486/78833