The Horn Plateau covers 25,000 square kilometres in the south-central part of the Northwest Territories. (CBC)

Members of the Dehcho First Nations are gaining support in their campaign to urge the federal government to restore a mining ban on a once-protected area of Northwest Territories wilderness.

Dehcho leaders were joined in Ottawa on Wednesday by Western Arctic NDP MP Dennis Bevington, who called on federal Indian and Northern Affairs Minister John Duncan to restore protection of the Horn Plateau.

The plateau is a 25,000-square-kilometre tract of land that is considered by the Dehcho to be culturally, spiritually and ecologically significant.

Last month, Duncan decided to open the plateau to subsurface development, even though the federal, territorial and Dehcho governments have been working on making it a national wildlife area under the N.W.T. Protected Areas Strategy.

Bevington said Duncan, who has only held his ministerial post since August, might simply have made a beginner's mistake.

"The new minister has really caused a problem here," Bevington told reporters in Ottawa.

"We can understand that, with someone who's new in a portfolio, [they might] … do this kind of thing. It can happen. But it can be undone, as well."

Neither Duncan nor the Indian and Northern Affairs Department has publicly explained the decision to date.

Sacred place

The Horn Plateau region, the source of three major rivers, serves as a nesting area for migratory birds and is a habitat for caribou, wood bison and wolverine species.

The Dehcho Dene consider the area — which they call Edehzhie in the Slavey language — to be a sacred place and an important hunting ground. It is also known to have potentially significant mineral deposits.

The plateau was covered by interim protection on surface and subsurface development from 2002 until last month while all parties worked out the terms of permanent protection.

Shortly before the interim protection was set to expire, Duncan's department issued an order-in-council extending that protection until 2012.

However, that extension retained only a ban on surface activities such as logging. Protection from subsurface activity such as mining and drilling was not included.

Bevington, along with Dehcho Grand Chief Sam Gargan and elder Jonas Antoine, said the decision goes against eight years of work they've done toward making the Horn Plateau a national wildlife area.

"We had an understanding that, right from the very beginning …we're going to have an area protected for all times, and then this happens," Antoine said. "So, it hurts us a great deal."

N.W.T. seeking reversal

The Northwest Territories government has also written letters asking Duncan to reverse his decision, as has the Canadian Boreal Initiative.

Executive director Larry Innes said up until now, the N.W.T. Protected Areas Strategy had been a model for working toward conservation on a national level.

"What shocked all of us was that now, someone can go in there today and stake mining claims and, basically, put eight years of work in jeopardy — in terms of protecting the very significant cultural and ecological values of the region," Innes said.

"From where we sit, that's just not the way things should be done, and it's certainly not the way things should be done through a protected areas process."