Duke University, Phys.Org
March 12, 2018
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
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
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
More information: John R. Poulsen et al, Ecological consequences of forest
elephant declines for Afrotropical forests, Conservation Biology (2017).
Journal reference: Conservation Biology
Provided by: Duke University
This news service is provided by Save the Elephants.