Forest Carbon Sequestration and the Essential Role of Wildlife

Forest Carbon Sequestration and the Essential Role of Wildlife

In a groundbreaking study, researchers from MIT and The Nature Conservancy have revealed that the decline in seed-dispersing animal populations significantly impacts the ability of tropical forests to absorb carbon. The study, published in PNAS, highlights the crucial role of these animals in facilitating forest regeneration and growth, key processes for carbon accumulation in regrowing forests.

The researchers found that most tropical trees (about 81%) rely on animals to disperse their seeds. When seed-dispersing animals decline, seed dispersal is disrupted, leading to lower tree survival rates, slower forest regrowth, and a significant reduction in carbon storage capacity. Studies show that this disruption causes an average 57% reduction in local carbon accumulation potential in tropical regrowth areas, translating to about 1.8 metric tons less carbon absorbed per hectare annually.

This relationship highlights a crucial feedback loop where biodiversity loss (decline in seed-dispersing animals) undermines climate change mitigation efforts by weakening forests' natural carbon sinks. The findings emphasize the importance of considering animal biodiversity preservation and climate change mitigation as interconnected issues, as supporting seed-dispersing animal populations enhances both forest health and carbon sequestration.

The study combines a wide array of data on animal biodiversity, movement, and seed dispersal across thousands of animal species, along with carbon accumulation data from thousands of tropical forest sites. The researchers created an index of seed-dispersal disruption that they used to analyze the relationship between that index and records of carbon accumulation in naturally regrowing tropical forests over time.

The researchers believe the findings open up new avenues of inquiry for the field, such as exploring how much of the decline in tropical forests' ability to sequester carbon is due to an increase in extreme droughts or fires versus declines in animal seed dispersal. They also encourage interventions that protect or improve habitats of seed-dispersing animals, ranging from wildlife corridors to restrictions on wildlife trade.

Restoring the ecological roles of seed dispersers is possible by reintroducing seed-dispersing species where they've been lost or planting certain trees that attract those animals. The researchers say the results are the clearest evidence yet that seed-dispersing animals play an important role in forests' ability to absorb carbon.

"Overlooking the impact of seed-dispersal disruption may overestimate natural regrowth potential in many areas and underestimate it in others," the authors write. "When we lose our animals, we're losing the ecological infrastructure that keeps our tropical forests healthy and resilient," says Evan Fricke, a research scientist in the MIT Department of Civil and Environmental Engineering.

The research was supported by the MIT Climate and Sustainability Consortium, the Government of Portugal, and the Bezos Earth Fund. The findings of the study improve our understanding of a potent tool to fight climate change and help us better comprehend the planet's complex ecological processes.

1. The research findings suggest that the decline in seed-dispersing animal populations significantly impacts the absorption of carbon by tropical forests.
2. The study published in PNAS reveals that the disruption of seed dispersal due to animal population decline leads to lower tree survival rates and slower forest regrowth.
3. The researchers used an index of seed-dispersal disruption to analyze the relationship between that index and records of carbon accumulation in naturally regrowing tropical forests over time.
4. The research emphasizes the importance of considering animal biodiversity preservation and climate change mitigation as interconnected issues, as supporting seed-dispersing animal populations enhances both forest health and carbon sequestration.
5. The researchers believe the findings open up new avenues of inquiry, such as exploring the role of extreme droughts or fires in the decline of forests' ability to sequester carbon.
6. The study encourages interventions that protect or improve habitats of seed-dispersing animals, such as creating wildlife corridors or restricting wildlife trade.
7. Restoring the ecological roles of seed dispersers could be achieved by reintroducing seed-dispersing species where they've been lost or planting certain trees that attract those animals, according to the researchers.

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