• New research analyzing more than 3,000 tropical forest sites reveals that areas with fewer seed-dispersing animals store up to four times less carbon than forests with healthy wildlife populations.
• The study found that 81% of tropical trees rely on animals to disperse their seeds, establishing an ancient partnership now threatened by human activities such as deforestation, road construction, and hunting.
• Researchers mapped global “seed dispersal disruption” and found it explains a 57% reduction in carbon storage potential across proposed forest restoration areas.
• The findings demonstrate that protecting wildlife and addressing climate change are interconnected challenges, with conservation strategies like wildlife corridors and species reintroduction offering approaches that serve both biodiversity and climate stability.

When a toucan plucks fruit from a tree in the Amazon Rainforest, it’s doing more than just finding lunch. Moving to a new location and depositing seeds via its droppings could be crucial in addressing climate change.

New research shows that when animals that spread seeds disappear, forests lose much of their ability to capture carbon from the atmosphere. The study, published in the *Proceedings of the National Academy of Sciences,*analyzed data from more than 3,000 forest sites across tropical regions worldwide.

Areas with fewer seed-dispersing animals store up to four times less carbon than forests with healthy animal populations.

“The results underscore the importance of animals in maintaining healthy, carbon-rich tropical forests,” study lead author Evan Fricke, from the Massachusetts Institute of Technology in the U.S., told Mongabay. “When seed-dispersing animals decline, we risk weakening the climate-mitigating power of tropical forests.”

Human activities have broken ancient relationships between animals and plants that have sustained forests for thousands of years. Roads block migration routes; deforestation destroys habitat; hunting reduces animal populations. Each disruption affects forests’ ability to store carbon.

The study found that 81% of tropical trees depend on animals to spread their seeds. Birds, mammals and other animals carry seeds to new locations, often traveling long distances. When forests are cut down, animals serve as nature’s delivery system for forest renewal.

A tapir and some of the seeds it disperses. Photo by Mauro Galetti.

“We know that in tropical forests, where more than three-quarters of trees rely on animals for seed dispersal, the decline of seed dispersal could affect not just the biodiversity of forests, but how they bounce back from deforestation,” Fricke said.

The findings show how biodiversity loss and climate change exacerbate each other. When animals disappear, forests store less carbon. When forests store less carbon, climate change gets worse. When climate change gets worse, more animals and plants face extinction.

“It’s been clear that climate change threatens biodiversity, and now this study shows how biodiversity losses can exacerbate climate change,” Fricke said. “Understanding that two-way street helps us understand the connections between these challenges, and how we can address them.”

This connection matters because forests currently absorb massive amounts of carbon (around 1.5 times more than the United States emits each year), making them one of our most important natural tools against global warming.

Anna Traveset, a research professor at the Spanish Research Council who studies seed dispersal, but wasn’t involved in the new research, told Mongabay that it “provides robust evidence that addressing biodiversity loss is inseparable from strategies aimed at climate change mitigation.”

She added, “By clearly linking animal biodiversity to forest carbon dynamics, the study highlights the critical importance of conserving animal species not only for maintaining ecosystem integrity but also for ensuring the role of tropical forests as major carbon sinks.”

A red howler monkey in the Tambopata Reserve, Peru. Primates and other mammals carry seeds far and wide. Image by Rhett A. Butler/Mongabay. To understand how seed dispersal affects forest carbon storage, researchers spent six years combining data from thousands of individual studies. They mapped how well animals can perform their seed dispersal function across different landscapes, rather than just mapping where animal species live.

The effort used seed dispersal data from 406 local networks, animal movement information from nearly half a million GPS locations across 80 species, and forest carbon measurements from tropical regions worldwide.

“We did a ton of work to be able to estimate how good the seed dispersers are at a location, and how much their ecological function has been disrupted,” Fricke said.

This approach revealed a global pattern the researchers called “seed dispersal disruption.” They found that in areas with more human development, animals move shorter distances when carrying seeds. When they compared this with measurements of carbon storage in regrowing forests, a pattern emerged: areas with more seed dispersal problems had much lower rates of carbon storage.

“It was a big task to bring data from thousands of field studies together into a map of the disruption of seed dispersal,” Fricke said. “It lets us go beyond just asking what animals are there to actually quantifying the ecological roles those animals are playing and understanding how human pressures affect them.”

The impact is large enough to influence global climate calculations. A bird’s flight path, repeated millions of times across landscapes, shapes how much carbon entire continents can store.

The “Corridors for Life” reforestation project in Brazil has restored connectivity to forest fragments in the Atlantic Forest. Many animals need connected forests to disperse seeds. Photo via IPÊ – Instituto de Pesquisas Ecológicas. “What’s particularly new about this study is we’re actually getting the numbers around these effects,” Fricke said. The research reveals that seed dispersal disruption explains a 57% reduction in carbon storage across areas identified as potential forest restoration sites.

The researchers identified specific factors that make natural forest regrowth more successful: areas that were recently deforested, locations near high-quality forests, and places with more existing tree cover tend to have better seed dispersal and faster carbon storage. This information could help governments and conservation organizations choose better locations for forest restoration projects.

“In the discussion around planting trees versus allowing trees to regrow naturally, regrowth is basically free, whereas planting trees costs money, and it also leads to less diverse forests,” study co-author César Terrer, an associate professor at MIT, said in a statement. “With these results, now we can understand where natural regrowth can happen effectively because there are animals planting the seeds for free, and we also can identify areas where, because animals are affected, natural regrowth is not going to happen, and therefore planting trees actively is necessary.”

The study suggests that conservation could benefit both biodiversity and climate goals. Creating wildlife corridors to help animals move between forest patches; reintroducing seed-dispersing species where they’ve been lost; and reducing human pressures on wildlife could all contribute to restoring seed dispersal.

“Understanding that there is a connection between animal biodiversity declines and the carbon stored in our ecosystems hopefully helps us make smarter decisions about aligning our responses to the biodiversity crisis and the climate crisis,” Fricke said.

Banner image of a Baird’s tapir courtesy of Esteban Brenes-Mora/Re:wild

Citations:

Fricke, E. C., Cook-Patton, S. C., Harvey, C. F., & Terrer, C. (2025). Seed dispersal disruption limits tropical forest regrowth. Proceedings of the National Academy of Sciences, 122(30), e2500951122. doi:10.1073/pnas.2500951122

Harris, N. L., Gibbs, D. A., Baccini, A., Birdsey, R. A., De Bruin, S., Farina, M., … Tyukavina, A. (2021). Global maps of twenty-first century forest carbon fluxes. Nature Climate Change, 11(3), 234-240. doi:10.1038/s41558-020-00976-6

As animals vanish, the plants they spread can’t keep pace with climate change

Liz Kimbrough is a staff writer for Mongabay and holds a Ph.D. in Ecology and Evolutionary Biology from Tulane University, where she studied the microbiomes of trees. View more of her reporting here.

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