Photo: The Canadian Press

An aerial view of Fort Chipewyan, Alta., on the boundary of Wood Buffalo National Park.

One of the world's largest groups of conservation scientists says Canada's biggest national park is among the most threatened World Heritage Sites in North America.

The International Union for the Conservation of Nature says Wood Buffalo National Park, which straddles the Alberta-Northwest Territories boundary, is significantly threatened by hydroelectric and oilsands development.

"This is quite embarrassing," said Melody Lepine of the Mikisew Cree First Nation, many of whose members live alongside the park.

"It's not looking good for Canada avoiding an endangered listing for Wood Buffalo."

Wood Buffalo is a vast stretch of grassland, forest, wetland and lakes. Its 45,000 square kilometres contain one of the world's largest freshwater deltas, uncountable flocks of waterfowl and songbirds, as well as ecological cycles and relationships that remain in their natural state.

It's also the nesting site for the last flock of endangered whooping cranes.

It is considered to have "outstanding and universal value," according to its status as a UNESCO World Heritage Site.

But the nature conservation union, which includes 1,300 member organizations and 10,000 experts, said those values have slipped considerably since the last report in 2014.

Only four other sites in North America are as threatened as Wood Buffalo — three in Mexico and one in the United States. Wood Buffalo is the only North American World Heritage Site to have deteriorated since 2014.

"The big threats are from hydro dam development," said Carolyn Campbell of the Alberta Wilderness Association.

Scientists have long warned about the slow drying of the Peace-Athabasca Delta from the Bennett Dam in British Columbia. BC Hydro's planned Site C dam is expected to worsen those effects.

"There's no water, no birds, no bison, no muskrats," Lepine said. "People are getting stuck on mudflats. They can't navigate. They can't get through to their hunting grounds or sacred sites.

"The loss of the delta is basically a loss of the Mikisew culture."