Elephants Are Knocking Down Too Many Trees In Kruger National Park, Researchers Say

African elephants are knocking down trees left and right in Kruger National Park, the largest protected area in South Africa, and a new study revealed that tree-fall rates in the park are all about elephant density there, which is growing. These large animals are the leading cause behind the area's changing ecology and shifting landscapes, because elephants routinely eat plants, tree bark, and other parts of trees.

"National parks and nature preserves will serve as biodiversity arks as we move into the future," Greg Asner, of Carnegie's Institution for Science, said in a news release. "But to manage them properly, conservationists will need to maintain the functionality of the ecosystem as a whole, which will require an understanding of system-wide responses to changing animal populations."

Protected areas, such as nature reserves and national parks, play a vital role in wildlife conservation. Essentially, they give threatened or endangered animals a place to live safe from the destruction or hunting dangers found in their natural habitats. For example, African elephant populations are greatly threatened by poachers who seek to rob them of their ivory tusks. African elephants are also the largest land mammal on Earth and need extensive areas of land with luscious plant growth, freshwater supply and space for their herds to move throughout, in order to survive. Therefore, their species is also significantly threatened by habitat loss or degradation of any sort.

Kruger National Park, which is located in northeastern South Africa, covers 1.9 million hectares and supports very large herds of elephants. Within the past 20 years alone, elephant populations in this national park have doubled, according to the release. However, populations may start to decline if conservationists aren't able to maintain a sustainable environment and manage the area's vegetation.

That's where researchers from the Carnegie Airborne Observatory come into play. To get a better sense of the rate of vegetation loss, researchers surveyed more than 10.4 million trees and woody plants across 19 landscapes within Kruger between 2008 and 2014. The Carnegie team, led by Asner, used an airplane-mounted Light Detection and Ranging (LiDAR) sensor to capture images and map vegetation in 3D. This allowed researchers to determine the different factors that were contributing to tree loss and rank them accordingly. On average, the team discovered a tree-fall rate of eight trees per hectare every other year. While topography, fire frequency and soil types contributed to this loss, the main factor was the high density of elephants living within the park. Their study -- the first of its kind -- was recently published in the journal Ecography.

"We know that Kruger has, in recent years, been undergoing changes in the size and distribution of its trees and other woody plants," Asner explained in the release. "Our findings suggest that these changes are, to a very large extent, driven by elephants. Since the population will continue to increase, our results will aid Kruger in addressing and managing the way the elephant population is shaping the park's vegetation."

On a much larger scale, this research contributes to understanding how the extinction of large prehistoric animals, such as mammoths who are ancestors of modern elephants, could have been impacted by their time period's ecology. Researchers examined this in a separate study published in the Proceedings of the National Academy of Sciences. Their study also provides valuable insight as to how conservationists can best manage the environments of protected areas.

"A combination of modern and paleoecological approaches can greatly improve our knowledge of animal-habitat interactions and the best ways to conserve biodiversity in an age of rapid extinction," Asner added in a statement.

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