A study by the University of British Columbia found the elephant population in the Okapi Faunal Reserve, one of the last strongholds of forest elephants in the Democratic Republic of Congo, dropped 50 per cent in the last decade due to civil war and ivory poaching.
The population fell from 6,439 to 3,288, and in other parks in the country the decimation was even greater, researchers said.
"Having protected areas is not enough to save elephants in times of conflict," lead author Rene Beyers of UBC's Department of Zoology said. "The war in the Democratic Republic of Congo had a large impact on elephant populations, including those in parks and reserves."
There are an estimated 6,000 elephants left in the wild in eastern Congo, down from approximately 22,000 before the civil war, the researchers said.
The war-torn country has the second biggest continuous rainforest in the world.
Most of this forest was probably elephant habitat in the past, scientists said, but poaching and human encroachment have taken a toll on the animals.