Defaunation affects carbon storage in tropical forests

Background

Tropical forests play a critical role in global carbon storage, holding approximately 40% of the Earth's terrestrial carbon. While deforestation, logging, and climate change are well-documented threats to these forests, the impact of defaunation (the loss of large frugivorous animals due to hunting and habitat loss) has been largely overlooked. Many large-seeded hardwood trees rely on large vertebrates for seed dispersal, and their decline could significantly affect forest composition and carbon storage.

Goals and Methods

This study aimed to quantify the effects of defaunation on carbon storage in tropical forests. The researchers used data from 31 Atlantic Forest communities in Brazil and analyzed 2,014 tree species, focusing on traits like seed size, wood density, and tree height. They modeled simulated defaunation scenarios, where large-seeded trees that depend on large frugivores were removed, and then compared these scenarios to random extinctions to assess the impact on carbon storage.

Conclusion

The results showed that defaunation leads to a decline in carbon storage by reducing the recruitment of large-seeded, hardwood trees. Even the loss of a small percentage (e.g., 10%) of large-seeded species resulted in a measurable reduction in carbon stocks. While some small seeded species persist, they do not provide the same level of biomass or carbon sequestration as large hardwood trees. Climate mitigation efforts (e.g., reforestation, REDD+ programs) must consider biodiversity conservation, as seed dispersers play a crucial role in maintaining forest carbon stocks.