Extinction of Earth's Largest Animals Could Make Climate Change a Lot Worse

December 22, 2015 | Joanne Kennell

A tucan
Photo credit: ...your local connection/Flickr (CC BY-NC-SA 2.0)

Many of these important species are already threatened.

If you need a reason to want to save animals from extinction other than the obvious “they are gone forever,” here is one:  According to research at the University of East Anglia, the extinction of large animals from tropical forests, such as primates, tapirs and toucans, could make climate change much worse.

How so?  Well, these large animals eat the fruit produced by large trees and in turn disperse some of the plant seeds through defecation.  These large trees often have high wood density — meaning they are better at capturing and storing carbon dioxide (CO2) from the atmosphere than smaller trees.  Therefore, the disappearance of these large animals would result in a loss of these large trees, which means less CO2 could be locked away.

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The team, led by researchers from São Paulo State University in Brazil, along with the UEA, the Spanish National Research Council (CSIC) and the University of Helsinki, Finland, looked at data from more than 2,000 tree species in Brazil’s Atlantic Forest and more than 800 animal species.  “We show that the decline and extinction of large animals will over time induces [sic] a decline in large hardwood trees,” said Professor Carlos Peres, from UEA’s School of Environmental Science.  “This in turn negatively affects the capacity of tropical forests to store carbon and therefore their potential to counter climate change.”

Unfortunately, several large species of vertebrates in tropical forests are threatened by hunting, illegal trade, and habitat loss, and the seeds of large trees are only dispersed by these large animals.  The researchers found that frugivores (animals who primarily eat fruit) that are not targeted by humans — such as small birds, bats and marsupials — can only spread small seeds, which are associated with smaller trees.

Carolina Bello, a PhD student from the São Paulo State University said, “When we lose large frugivores we are losing dispersal and recruitment functions of large seeded trees and therefore, the composition of tropical forests changes. The result is a forest dominated by smaller trees with milder woods which stock less carbon.”

Current policies in place to reduce CO2 emissions from tropical countries have focused primarily on deforestation, with a lesser focus on forest degradation.  However, this research points to the importance of a proper functioning ecosystem to maintain carbon storage.  “We hope that our findings will encourage UN programmes on Reducing Emissions from Deforestation and Forest Degradation (REDD+) to consider faunally intact forests and their full functionality as a critical precondition of maintaining forest carbon stocks,” said Peres.

Not only should we feel morally obligated to save these animals from extinction — since we are responsible for most of their disappearances — but we also depend on many of these plant and animal species for food, medicine, air and water purification, and moderating the climate.  With proper conservation programs in place, we can save and preserve these important ecological systems as well as help ourselves by maintaining the amount of carbon captured by these tropical forests, keeping it out of the atmosphere.  Win-win.

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