Conserving populations of endangered forest elephants is vital not only for the animals themselves, but also to protect the carbon-seizing capacity of the environments they live in, a new study shows.
The rainforest in central and west Africa, the second largest on earth, could lose 6 to 9 percent of its atmospheric carbon sequestration capacity if elephant communities were wiped out – further accelerating the planet’s warming.
Forest elephants play a crucial role in this carbon cycle, “thin” the rainforest canopy by eating fast-growing, taller trees that absorb less carbon. This creates more space and sunlight for the slower-growing trees below, which absorb more carbon from the environment.
“If we lose forest elephants, we are doing them a disservice around the world climate change mitigation”, says biologist Stephen Blake from Saint Louis University in Missouri.
“The importance of forest elephants to climate change mitigation needs to be taken seriously by policy makers in order to generate the support needed for elephant conservation. The role of forest elephants in our global environment is too important to ignore.”
Using data from previous studies and new information gathered in the field, the team analyzed nearly 200,000 records of feeding patterns of forest elephants in Africa, covering more than 800 individual plant species.
Elephants’ preference for trees with lower carbon density appears to be due to the nutritional value they get from them rather than their availability: they are more palatable to the animals and easier to digest.
However, in terms of fruit, the elephants prefer higher carbon density trees, which have larger and sweeter fruit. This means that the elephants also help out distribute seeds for these carbon-rich trees further around the forest. Some tree species cannot even survive without the help of these animals.
“Elephants eat many leaves from many trees, and they do a lot of damage while eating.” says Blake.
“They are removing leaves from trees, tearing off an entire branch, or uprooting a sapling when they eat, and our data shows that most of this damage occurs on low-carbon-density trees.
“If there are a lot of high-carbon-density trees, that’s one less competitor to be eliminated by the elephants.”
There are thought to be fewer than 500,000 African elephants in the wild, fewer than 3-5 million in the last century. Ivory hunting is responsible for this drastic decline, with 80 percent loss of herds in some areas. Habitat loss and human-elephant conflict further reduce population numbers.
This new study highlights the importance of protecting these African elephants, the largest animals on Earth. They are one of 9 species of megaherbivores – terrestrial herbivores with a body mass exceeding 1,000 kilograms or 2,200 pounds.
There are far fewer megaherbivores today than there used to be, and tropical forests are suffering, the researchers say. Future studies are now planned looking at other regions and other species to see how other large herbivores like the Asian elephant and primates might affect rainforest health.
“Elephants are the gardeners of the forest” says Blake.
“They plant the forest with high carbon density trees and they weed, which are the low carbon density trees. They do an enormous amount of work to preserve the diversity of the forest.”
The research was published in PNAS.
