Loss of elephants (and their poop) devastates forests

"The message that 'guns kill trees, too' should help put overhunting at the top of the conservation agenda, where it deserves to be," says Richard Corlett. (Credit: iStockphoto)

Elephants in Thailand have traditionally been hunted, mostly for fabled properties of their organs, teeth, and tusks. But a new study shows that overhunting has been disastrous for their tropical forest habitats.

Elephants disperse lots of seeds across the forest. The dramatic loss of elephants increases the probability of tree extinction by more than tenfold over a 100-year period—a process that will likely cascade to other kinds of forest life, researchers predict.


“The entire ecosystem is at risk,” says Trevor Caughlin, a postdoctoral student at University of Florida. “My hope for this study is that it will provide a boost for those trying to curb overhunting and provide incentives to stop the wildlife trade.”

For a new study published in the Proceedings of the Royal Society B, researchers looked specifically at how vital elephants are to maintaining the biodiversity of tropical forests in Thailand by moving seeds around.

The elephant has long been an important spiritual, cultural, and national symbol in Thailand. At the beginning of the 20th century, their numbers exceeded 100,000. Today, those numbers have plunged to 2,000.

Millions of seeds

Caughlin spent three years gathering tree data in Thailand, looking at the growth and survival of trees that sprouted from the parent tree and grew up in crowded environs, compared with seeds that were transported and broadcasted widely across the forest by animals.

The data were supplemented with a dataset from the Thai Royal Forest Department that contained more than 15 years of data on trees to create a long-term simulation run on a supercomputer.

Trees that grow from seeds transported by those animals that are being overhunted are hardier and healthier.

“Previously, it’s been unclear what role seed dispersal plays in tree population dynamics,” Caughlin says. “A tree makes millions of seeds during its lifetime, and only one of those seeds needs to survive to replace the parent tree.

“On the surface, it doesn’t seem like seed dispersal would be that important for tree population. What we found with this study is that seed dispersal has an impact over the whole life of a tree.”

‘Guns kill trees, too’

“Our study is the first to quantify the decades-long effects of animal seed dispersal across the entire tree life cycle, from seeds to seedlings to adult trees,” says Jeremy Lichstein, assistant professor of biology one of the paper’s authors.

Richard Corlett, director of the Center for Integrative Conservation at the Xishuangbanna Tropical Botanical Gardens in Yunnan, China, underscored the study’s importance.

“This study fills a major gap in our understanding of how overhunting affects forest trees, particularly in tropical forests. We knew hunting was bad, but we were not sure why it was bad, and therefore could not predict the long-term impacts.

“Now we know it is really, really bad and will get worse. The message that ‘guns kill trees, too’ should help put overhunting at the top of the conservation agenda, where it deserves to be.”

Other researchers from University of Florida and from the Conservation Ecology Program in Thailand, Wageningen University in the Netherlands, and the Royal Thai Forest Department, contributed to the study.

Source: University of Florida