POWELL -- The number of grizzly bear deaths in the greater Yellowstone ecosystem increased markedly this year, but the population still continued to grow.

According to the Interagency Grizzly Bear Study Team, an estimated 80 grizzlies died in the Yellowstone area in 2008. In 2007, 49 grizzlies died.

The numbers of grizzly deaths are estimated from known, probable, estimated unknown and unreported deaths from a variety of causes, according to Interagency Grizzly Bear Study Team figures.

Despite the deaths, the grizzly population in the ecosystem increased an estimated 4 percent this year.

In 2007, there were an estimated 571 grizzlies. In 2008, the number increased to an estimated 596 grizzlies.

Based on those figures, the population will double in 20 years, said Chuck Schwartz, Interagency Grizzly Bear Study Team leader in Bozeman, Mont.

This year's deaths exceeded the limit set by the U.S. Fish and Wildlife Service for sustainable population growth.

"One year doesn't make a trend," Schwartz said.

However, grizzly bear managers across the region will keep close tabs on population numbers next year to ensure there is no decline, Schwartz said.

"The agencies are on top of it," he said.

Too many bear deaths over consecutive years could result in the bears being returned to endangered status.

In March 2007, the U.S. Fish and Wildlife Service removed Yellowstone-area grizzlies from endangered species status.

Even if the population drops to 500 bears, a lot of review and monitoring would be done before relisting, Schwartz said.

But Schwartz noted that conservation groups have a number of lawsuits filed against the U.S. Fish and Wildlife Service. If those lawsuits are successful, grizzly bears in the Yellowstone ecosystem could return to endangered status.