Programs around the world have tried to harness the power of money to save habitat, by paying people to protect or restore their land.
When ecologist Giacomo Delgado wanted to test whether one of the oldest and most established programs was translating into biodiversity gains, he chose to listen for it.
Using more than 100 weatherproofed microphones and powerful computer programs, the Ph.D. student at the Swiss Federal Institute of Technology in Zurich (ETH Zürich) collected nearly a million minutes of audio recordings from land scattered across Costa Rica’s Nicoya Peninsula.
The results revealed that the din of life in forests regrowing under a program that paid landowners to leave pastureland untouched had a lot in common with intact forests in the area, Delgado and colleagues reported recently in Global Change Biology.
“These findings represent perhaps some of our best evidence to date that ecosystem restoration can benefit biodiversity at large spatial scales,” Delgado wrote in a blog post.
The subject of his study was an experiment begun in Costa Rica in 1996, the first nationwide program in the world that paid people to preserve land and the underlying environmental benefits. The program is funded chiefly through a tax on fossil fuels, and has been credited with helping the country become a place growing more forest than it loses.
But until Delgado picked up his microphones, it wasn’t clear that this forest renewal had translated into a revival of forest inhabitants. While he might have opted to try the painstaking approach of counting individual animals in a small number of places, the scientist opted to tap into the burgeoning field of bioacoustics, in which mountains of digital recordings are crunched by computers to understand the natural world.
He and collaborators placed microphones on 142 sites in the peninsula, a mix of native forest, pasture, and sites that had been allowed to recover on their own or been replanted with a single tree species as part of the national program. They emerged with 999,470 minutes of audio data recorded between May and July 2022.
Using computers, they developed a kind of fingerprint of the soundscapes for each kind of land. Natural forests were raucous – loud and marked by lots of variation in sounds, particularly around dawn and dusk. Birds and insects were particularly noisy during twilight. Pastures, by contrast, had far more human sounds, no big burst at sunrise and sunset, and more noise at night.
The former pasture turned young forest, where people were paid to let it regrow, bore many of the hallmarks of the intact forest, particularly during the dusk burst of activity. Overall, it was 1.4 times more similar to the natural forests than to the pastures. The sounds of the replanted forests lagged behind a bit, at 1.24 times more similar the natural forests.
The regrowing forests still had a way to go before they were indistinguishable from old growth. In particular, the dawn chorus was more muted. That might be because biodiversity in those altered landscapes still lags, or because nearby human activity quieted the creatures, the scientists suggested.
For Delgado, the results offer hope for ecological restoration and for simultaneously bringing economic benefits to the people, many of them poor, who live on and protect the land. “Empowering local people and sharing nature’s bounty among all, instead of locking it away for the privileged few, is a radically effective ecological solution,” he wrote.
Delgado, et. al. “Large-Scale Forest Restoration Accompanied by Biodiversity Recovery in Costa Rica’s Redistributive Payment for Ecosystem Service Program.” Global Change Research. Feb. 4, 2026.
Image: ©Anthropocene Magazine
