Hungry elephants fight climate change one mouthful at a time

Jul 16, 2019 | News

By  Eva Frederick – ScienceMag

African forest elephants can eat up to 450 kilograms of vegetation a day as they plow through the rainforests of West Africa and the Congo Basin. But all this munching actually leads to forests with more plant mass, according to a new study, and it could be good for climate change.

As African forest elephants (Loxodonta cyclotis, above) graze, they munch trees and plants with stems smaller than 30 centimeters in diameter—a little wider than a basketball—often damaging or killing them. Researchers used a model to predict what a forest might look like after years of elephants eating down these smaller plants. The bottom line: Slow-growing, shade-tolerant trees thrive with less competition for water and sunlight. The resulting forest has fewer, taller trees with denser wood, and the overall mass of vegetation above the ground is higher, meaning more carbon is stored, the team reports on today in Nature Geoscience.

The model’s predictions checked out in the real world, too. Trees in forests where elephants live had denser wood by about 75 grams per cubic meter than those in forests without elephants. Even just one elephant per square kilometer could increase the amount of plant mass in the forest by up to 60 tons per hectare, enough to suck up more than 10 billion tons of planet-warming carbon dioxide across Africa’s 2.2 million square kilometers of forest. As elephants disappear—which they are doing at an alarming rate—those same forests will be less able to help fight climate change.

Elephants’ effects on forest ecosystems may also explain why rainforests look different from continent to continent. A walk through the elephant-free Peruvian Amazon, for example, is a much different experience than a trek through a rainforest in the Republic of Congo, which has smaller, more tightly packed trees despite similar climate and soil conditions. The researchers speculate that elephants help drive these ecosystem changes over hundreds of years.