Loss of Large Mammals Could Change Entire Ecosystems

First Posted: Oct 26, 2015 08:42 PM EDT

When we lose large mammals to extinction, we don't just lose them; we also lose their poop. Now, scientists have found that the loss of large mammals may just change landscapes forever.

In this latest study, the researchers examined the ecosystem impacts of large animal, or megafauna extinctions in the Americas since humans moved in about 15,000 years ago. The scientists found long-lasting changes in the local landscape after the largest of the land animals-among them mammoths and mastodons-disappeared.

But what kind of changes occur? Mastodons, mammoths and today's elephants eat small trees and shrubs and uproot or break down trees as well as trample and churn the soil. Other large herbivores, such as bison and moose, also keep shrubs in check and change soil structure and nutrients as they feed, defecate and urinate. This means that these plant eaters play a key role in keeping forests from overrunning grasslands.

The nutrients that these large animals return to the soil largely determine what sort of ecosystems exists in an area.

"You see the impact of defaunation today in Africa, where the removal of elephant populations has led to these shrubby, scraggly acacias filling the savanna landscape," said Charles Marshall, co-author of the new study, in a news release. "Africa today, with its elephant populations, seems to fit the model of North America with its mammoths and mastodons."

Understanding these relationships between large mammals and flora can be huge when it comes to targeting conservation efforts. It could be especially useful to conservation biologists in pinpointing which types of ecosystems are likely to be affected by global climate change.

"If we lose some of these big-bodied animals that are threatened with extinction today, we lose a lot more than those animals, we lose the entire ecosystems of which they are a part," said Anthony Barnosky, one of the researchers. "We are moving into new territory in terms of what the planet will look like."

The findings are published in the journal Proceedings of the National Academy of Sciences.

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