An aerial view of the Selkirk Mountains and the Darkwoods lands. (Nature Conservancy of Canada)

The federal government and Nature Conservancy Canada have announced a plan to preserve 550 square kilometres of remote valleys, mountains and lakes in the southern interior of British Columbia that may save an endangered herd of mountain caribou.

The acquisition of the property, known as Darkwoods, is one of the largest single private conservation project ever undertaken by a Canadian non-profit organization, the Nature Conservancy said in a statement released Thursday.

With support from the federal government, the land, which is situated between the towns of Nelson, Salmo and Creston in the West Kootenay, was acquired from the German-based Pluto Darkwoods Forestry Corporation for more than $125 million.

"This is truly an incredible property both in size and value, covering an area nearly 140 times the size of Stanley Park," Federal Environment Minister John Baird said in Vancouver on Thursday.

"The property that we're excited about today is invaluable in our efforts to protect animals like the [mountain] caribou — not only for its size but for the important connection it provides between existing conservation areas," Baird said.

Craig Pettitt of the Valhalla Wilderness Society said the plan is superior to the one put forth by the B.C. government last fall because it gives the 45 members of the South Selkirk mountain caribou herd a decent shot at survival.

"It includes all ranges of [mountain caribou] habitat, whereas the B.C. government's plan restricts habitat, which means it's largely aiming at high elevation habitat, Pettitt said.

"Conserving Darkwoods is essential to the recovery of the South Selkirk caribou population," agreed biologist Trevor Kinley. "It could also significantly affect the viability of the local grizzly population, and it will definitely influence the retention of natural biodiversity."

There are only about 1,900 southern mountain caribou left in B.C., down from 5,000 about 20 years ago. The remaining population is spread out among 11 herds.

The Nature Conservancy of Canada, which is a private, non-profit Canadian organization dedicated to protecting the country's most ecologically significant lands, is now working closely with local communities to develop the management plans that will support and sustain Darkwoods for the long term, it said.