What could be worse than large-animal extinction from tropical forests? The answer: its major consequence on climate change, according to UK researchers in their new study.
Researchers from the University of East Anglia, publishing their findings Dec. 18 in the journal Science Advances, revealed that a decline in large primates and other fruit-consuming animals had a potential knock-on effect for trees.
This could then hold grave consequences in the fight against climate change.
"We show that the decline and extinction of large animals will over time induce a decline in large hardwood trees. This in turn negatively affects the capacity of tropical forests to store carbon and therefore their potential to counter climate change," said study author and UEA professor Carlos Peres.
The team made up of researchers from Brazil's São Paulo State University, UEA, Finland's University of Helsinki, and the Spanish National Research Council studied data from over 2,000 Atlantic Forest tree species in Brazil and over 800 animal species.
The danger lies in the loss of wood-heavy large tree species, whose seeds large animals disperse through ingestion and passing intact through their digestive tract. These large trees better capture and store carbon dioxide than smaller varieties.
The researchers explained that when these large animals become extinct, the ecosystem's natural balance will be upset; with the loss of large trees translate to less carbon dioxide being locked away.
Peres cited threats against birds and mammals that perform seed dispersal for large-seeded plants. "Several large vertebrates are threatened by hunting, illegal trade and habitat loss," he said, warning that the steep decline of tropical megafauna can lead to massive unforeseen impacts.
Smaller animals not targeted by hunters and poachers, including bats and small birds, ably dispersed only small seeds linked to small trees.
"The result is a forest dominated by smaller trees with milder woods which stock less carbon," São Paulo State University Ph.D. student Carolina Bello predicted with the loss of larger animals.
The Amazon and other tropical forests are the biggest and densest natural carbon sinks on Earth, acting as the planet's lungs and inhaling over a quarter of carbon emissions. They store these emissions in the trunks and roots of trees.
Peres hoped that their findings will spur U.N. programs that consider the challenge of defaunation in maintaining forest carbon stocks. Current policies for carbon emission reductions, he added, primarily focused only on deforestation.
Photo: Miki Yoshihito | Flickr