VANCOUVER - Hunting grizzly bears puts even more pressure on a species already in jeopardy from shrinking habitats, poaching and global warming, says a group of scientists and conservationists calling on the B.C. government to end the hunt.

The coalition has written to Premier Gordon Campbell, saying the bear population is declining and the numbers used by the government to manage the hunt are unreliable.

"Because the numbers are really unknown and not reliable, the effect of the hunt can't be fully predicted," said Paul Paquet, a wildlife expert based at the University of Calgary.

The B.C. Environment Department currently estimates there are about 17,000 grizzlies in B.C.

But Paquet, who has served on scientific advisory panels focusing on grizzly bears for the B.C. government, said the methods used to reach that figure rely on estimates that are open to wide margins of error.

"It could be 17,000, but it could also be 5,000," he said.

"The major issue for me is we really don't know how many grizzly bears there are, and if you consider the future of B.C., in terms of everything from mining to forestry to more roads, that's a problem."

The letter says grizzlies are already suffering from loss of habitat due to industrial logging, mining and energy developments, and could lose a major food source if climate change disrupts the salmon population.

The signatories of the letter - nearly five dozen researchers and conservationists mostly from Canada and the United States - say B.C. should err on the side of caution rather than needlessly put the grizzlies at greater risk.

Neither the premier nor the environment minister were available for comment Tuesday, but the Environment Department says its estimates are "thorough and conservative" and are backed up by established science

The department also says it reviews quotas every year to ensure grizzly kills do not exceed a five-year running limit.

Scott Ellis of the Guide Outfitters Association of B.C., which represents the guides who must accompany non-residents on a hunt, said the province has spent millions on conservation and improved tracking, and he stands by the government estimate.

Even though grizzlies are considered a species at risk, Ellis insisted hunting a few hundred a year won't have a major impact.

"The total kill, total harvest is two per cent - it's insignificant," said Ellis.

The B.C. grizzly population is listed as a vulnerable, at-risk species by the province and a species of special concern by the federal government.

The province estimates B.C. is home to half of Canada's grizzly population, and a quarter of all grizzlies in North America.

Grizzly hunting is restricted in parts of the province, including in an area known as the North Cascades in the southern Interior, but hundreds are still hunted each year during fall and spring openings.

Earlier this year, hunt critics released provincial government statistics that showed 430 grizzly bears were killed in 2007.

Populations in the northwestern United States and in Alberta have been devastated, and they are steadily declining in British Columbia, said Paquet.

"Right now you're really looking for the last refuges for grizzly bears," said Paquet, referring to the B.C. population.

The letter says B.C. has failed to implement additional no-hunting zones as promised more than a decade ago in species management plans.

"There's a couple of places that have had bans in place for a long time, but pretty much the rest of the entire landscape, whether it's a conservancy are not, is open," said Chris Genovali of the Vancouver Island-based Raincoast Conservation Society.

The letter also says the hunt in Canada could compromise conservation efforts in the U.S., since part of that recovery could depend on grizzlies migrating south from Canada.

"Here in the United States, we've already eradicated most of our grizzly bears," Spencer Lennard of the Oregon-based group Big Wildlife said in an interview.

Lennard said Canadian jurisdictions have a responsibility to protect a species with such ecological and symbolic importance.

"We (the United States) have made a horrible mistake by ridding ourselves of this incredibly beautiful and very ecologically important species," said Lennard.

"So I would hope that the B.C. government does not make the same terrible mistake."

Shane Simpson, the environment critic for the Opposition NDP, noted that the previous New Democrat government implemented a moratorium on grizzly hunting in 2001, only to have it overturned a few months later after the Liberals took power.

"We called for the halt until we could get some good numbers that everybody could agree on," said Simpson.

"We shouldn't be hunting the bear until we know what we're talking about, and then we can have an intelligent conversation about what the status of it is."