H.S. Sathya Chandra Sagar stood among Gola Rainforest National Park's tallest trees and heard what sounded like a living orchestra: the calls of countless birds, the hoots of primates, and in the distance, the drumming of chimpanzees beating fists and sticks on tree roots to communicate with friends miles away. That symphony of sound, Sagar realized, might be telling him something crucial about whether protecting forests for carbon actually protects the animals that live there too.
Gola Rainforest National Park sits in Sierra Leone, part of what remains of the Upper Guinean Tropical Rainforest—a forest that once sprawled across 700,000 square kilometers of West Africa before a century of mining, logging, and a devastating 1990s civil war reduced it to fragments. In 2010, Sierra Leone protected 700 square kilometers of the surviving forest. Two years later, in 2012, the government established the Gola REDD+ project, joining the United Nations Reducing Emissions from Deforestation and forest Degradation program, which rewards countries for not cutting down trees by issuing carbon credits that can be sold to higher-emitting nations. Previous research showed the strategy was working: REDD+ interventions reduced deforestation by 30 percent in the park compared to neighboring areas.
But Sagar, a conservation biologist at the University of Wisconsin-Madison, wanted to know if something else was happening too. Had the forest protection that saves carbon also saved the creatures living there? To answer that question, he and his colleagues took advantage of a unique geographical circumstance. Just across the border in Liberia sat an 800-square-kilometer protected area with similar wildlife and habitat—but no REDD+ financing. Gola also shared a border with a community-owned agroforestry region that received REDD+ support but no formal protection. These three landscapes became living laboratories.
The team deployed passive recording devices at 133 sites across all three areas to capture 24-hour soundscapes. Using what ecologists call the "acoustic niche" hypothesis—the idea that animals in noisy environments adapt to unique sound frequencies so their calls stand out like individual instruments in an orchestra—the researchers measured how much sound each site contained and at what frequencies. Areas with greater sound diversity are thought to indicate greater biodiversity. The results, published in Conservation Science and Practice, were striking: soundscape saturation was significantly higher in Gola Rainforest National Park than in either comparison area, suggesting richer animal communities thriving throughout the day.
The study also examined DNA richness from insects and found something more complex: while Gola had greater overall biodiversity signals, the community-owned agroforestry area actually had higher insect diversity. This nuance matters. The findings suggest that carbon financing programs, when implemented well, can protect biodiversity alongside carbon sequestration—but that different approaches have different trade-offs.
"We see that if it's done well, carbon financing initiatives do have the capability to protect both biodiversity, beyond just habitat, and carbon markets," Sagar says. Experts emphasize that the study highlights something equally important: on-the-ground monitoring can be cheaply and effectively added to programs like REDD+ to ensure forests thrive as whole ecosystems, not just as carbon repositories. In a world where forests increasingly compete for funding against other conservation needs, proving they can do double duty—storing carbon while sustaining the creatures that depend on them—may be the argument that saves them.