An expansion of the Nahanni National Park Reserve announced this week by the prime minister has left proponents wondering how the park can coexist with a nearby zinc mine — a case even Stephen Harper acknowledged makes for strange neighbours.

On Wednesday, Harper, on a three-day visit to the North, said in Fort Simpson, N.W.T., that 5,400 square kilometres of land would be added within the Greater Nahanni ecosystem, protecting it from any further development.

The newly protected area is in addition to 23,000 square kilometres of land already under interim protection by the Dehcho First Nations that includes the park area in its territory. The park covered about 4,700 square kilometres when it was created in 1972.

But the new boundaries do not include the Prairie Creek mine site on the park's edge.

Environmentalists and other park proponents had hoped Harper would extend the boundaries to include the entire south Nahanni River watershed, far enough to include the mine.

"It's obviously uncomfortable," Harper said. "But at the same time, we recognize that we're required by law to respect existing rights."

The zinc, silver and lead mining project was built a decade after former prime minister Pierre Trudeau established the reserve in 1972 to protect it from proposed hydroelectric development.

The mine, with an ore body worth an estimated $2.5 billion, has yet to go into production — something current owner Canadian Zinc Corp. has been working for years to start, despite an ongoing battle with Parks Canada and environmental groups over permits.

No 'light at end of tunnel': negotiator

Whitehorse resident Neil Hartling, who leads visitors on tours through Nahanni National Park, said expanding the park's boundaries doesn't mean much if it doesn't keep mining operations out.

"Sadly, what it means is that the large area taken up by the footprint from the mine — and the outwash from it, and the road that they want to put into it — really cuts off a grand portion of the watershed that we were hoping to protect," said Hartling, the owner of Nahanni River Adventures.

Canadian Zinc, a Toronto-based junior exploration company that has the Prairie Creek mine as its main project, recently won the right to re-establish a winter road at the site. Company president John Kearney told CBC News that the mine will be a good neighbour to the park.

"We do not believe that the mine will interfere with the park in any way, or in any way have any adverse effect on its ecological integrity," he said Wednesday.

Jonas Antoine, who has been negotiating for park expansion on behalf of the Dehcho First Nations, said he is looking for a way to satisfy elders who want the watershed protected, while at the same time avoiding more wrangling with Canadian Zinc.

"I'd like to see a light at the end of the tunnel, which I don't see yet," Antoine said. "I get a little glimmer once in a while, but not bright enough."

Antoine suggested better protection of the water flowing from the mine into the Nahanni may be the key to coexistence.

The park expansion is now subject to public consultation, expected to take place this fall.