Large fruit-eating mammals and birds play a role in fighting climate change, and if we drive them to extinction, we will make a hotter world in the process, new research suggests.

It might sound like the end of “Avatar, ” but fruit-eating animals are guerrilla warriors( or maybe gorilla warriors ?) against global warming. Their sizing enables them to devour and disperse big seeds, particularly those that go surrounded by juicy fruit.

Although mighty oaks from little acorns grow, big hardwood trees that store the most carbon tend to have bigger fruit.If forests are to continue absorbing carbon from the atmosphere these trees need a mechanism to scatter their seeds.

Not only do these furred and feathered Johnny Appleseedsdistribute fruit to places far away from the parental tree, they often provide essential processing for the seeds to sprout. Many fruits cannot grow until they have passed through the digestive tractof a large animal sometimes depending ona specific species.

Professor Carlos Peresof the University of East Anglia joined a Brazilian analyse of the effects on seed dispersal in more than 2,000 tree species when animals become locally extinct. The outcomes, published in Science Advance, disclose just how important this natural seed bombing is to the health of the planet.

“Large birds and mammals provide nearly all the seed dispersal services for large-seeded plants. Several large vertebrates are threatened by hunting, illegal trade, and habitat loss. But the steep decline of the megafauna in overhunted tropical wood ecosystems can bring about large unforeseen impacts, Peres said in a statement.”We show that the deterioration and extinction of big animals will over time induce a decline in big hardwood trees. This in turn negatively affects the capacity of tropical forests to store carbon and therefore their potential to counter climate change.”

How larger animals spread fruit in a healthy forest. Credit: Peres/ University of East Anglia

Smaller birds and bats also disperse seeds, but unsurprisingly merely small ones, with a maximum period of 12 millimeters( 0.5 inches) identified in the paper. The writers found that when hunters target larger animals the consequences for long-term forest regeneration are dire. They note: Unsustainable hunting is a worldwide problem that has increasedin the last few decades over tropical forests.

Plants with seeds above the 12 mm limit represented 21 percentof the specimen analyzed, but holdthe majority of the stored carbon in Brazil’s Atlanticrainforests. We find a greater loss of carbon as the percentage of removed large-seeded tree species increases, as a consequence of defaunation of big frugivores, the authors report.

Intergovernmental policies to reduce carbon emissions from tropical countries have primarily focused on deforestation, and to a lesser extent on forest degradation resulting from timber extraction and wildfires, saidPeres. But our research shows that a decline in large vertebrate populations and the loss of key ecological interactions also poses a serious risk for the maintenance of tropical woodland carbon storage.

As the paper points out: Tropical woodlands store 40 percent of the world’s terrestrial carbon and their deforestation contributes to 7 to17 percentof global carbon emissions.

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