Duke University, Phys.Org

Tim Lucas

March 12, 2018

See link

<https://phys.org/news/2018-03-elephant-declines-imperil-africa-forests.html>

for photo.

Poaching and habitat loss have reduced forest elephant populations in

Central Africa by 63 percent since 2001. This widespread killing poses dire

consequences not only for the species itself but also for the region’s

forests, a new Duke University study finds.

“Without intervention to stop poaching, as much as 96 percent of Central

Africa’s forests will undergo major changes in tree-species composition and

structure as local populations of elephants are extirpated and surviving

populations are crowded into ever-smaller forest remnants,” said John

Poulsen, assistant professor of tropical ecology at Duke’s Nicholas School

of the Environment.

These changes will occur because elephants are ecological engineers that

help create and maintain forest habitat by dispersing seeds, recycling and

spreading nutrients, and clearing understories, Poulsen explained.

“Because they are very large animals, they can eat fruits and disperse

seeds too big for other animals to digest. And because they are highly

mobile, they help disperse these seeds far and wide through their dung,” he

said.

In the elephants’ absence, scores of tree species may be left without a

means of long-distance seed dispersal, which is essential for forest

structure and colonization. Trees whose seeds are dispersed by smaller

animals could fill the void, dramatically altering forest composition.

Fewer elephants will also mean a more limited distribution of the nutrients

contained in their dung.

“Many of Central Africa’s forests are nitrogen limited. Elephants help

compensate by moving nutrients, especially nitrogen, across the landscape

as they defecate. If populations continue to shrink, this nitrogen will be

concentrated in smaller and smaller areas, limiting future tree growth

elsewhere,” Poulsen said.

Understory density will also be affected.

“Elephants have a large effect on forests by eating or trampling

slow-growing plants and opening the understory, allowing more light in and

reducing competition for water and nutrients,” Poulsen said. “These changes

alter the recruitment regimes of tree species?favoring some and not

others.”

He and his colleagues published their peer-reviewed study March 1 in the

journal Conservation Biology.

To conduct their analysis, they reviewed 158 previous studies on forest

elephant behaviors and their cascading ecological impacts.

By cross-referencing these impacts with data on local elephant populations,

forest tree-species composition and structure, nutrient availability, and

understory growth in existing Central African forests?both protected and

unprotected ones alike?Poulsen and his team determined that up to 96

percent of all forests in the region were susceptible to dramatic changes

if elephant populations shrank or disappeared.

“Stopping poaching is an urgently needed first step to mitigating these

effects,” he said, “but it will not be easy. Long-term conservation will

require land-use planning that incorporates elephant habitat into forested

landscapes that are being rapidly transformed by industrial agriculture and

logging.”

More information: John R. Poulsen et al, Ecological consequences of forest

elephant declines for Afrotropical forests, Conservation Biology (2017).

DOI: 10.1111/cobi.13035

Journal reference: Conservation Biology

Provided by: Duke University

https://phys.org/news/2018-03-elephant-declines-imperil-africa-forests.html

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