A death sentence has been passed on the beavers living in a small lake in the Gulf Islands, but concerned citizens are hoping they can force a last minute pardon.

The rodents have been busy building dams in South Pender Island's Greenburn Lake.

Parks Canada, which administers the area as part of the Gulf Islands National Park Reserve, says the beavers' work is threatening an earthen dam.

Officials say they've exhausted all other options and have no choice but to humanely trap and euthanize the animals. But local residents are planning a blockade in an attempt to get the execution called off.

"We're actually horrified by the fact that they would dream of killing wild animals when their mandate is to protect the wilderness and wild animals," Leslie McBain told CBC News.

"It is ironic that their symbol, the National Parks symbol, is a beaver."

'A very difficult decision'

Nathan Cardinal, acting superintendent for the park, said he's sympathetic to concerns from the public.

"Having to take these steps is a very difficult decision for the agency and everyone involved," he said.

"We respect the right for people to protest, for sure, and we acknowledge that many people on the island care about the beavers. For us, euthanizing a problem animal is always the last resort."

Between one and eight beavers have made their homes in the lake and, as they construct their own dams, more and more water is building up behind the man-made dam, threatening its structural integrity.

Cardinal said that if the beavers are allowed to continue living in the lake, the dam will fail, causing water to spill onto people's properties and into their homes.

"At Parks Canada, it's our mandate to ensure ecological integrity, but we always have to ensure that public safety comes first," he said.

Parks officials have been looking at potential solutions for about a year.

They've tried installing something called a "beaver deceiver" — a rectangular fence protecting a culvert that allows water to flow through — but the rodents responded by building dams in new places, causing more backup.

Parks officials have also looked into relocating the animals. But Cardinal said beavers are both territorial and increasingly abundant across B.C., so staff couldn't find a suitable new home.

Time running out

Now that it's November, Parks Canada feels compelled to act.

"We need to address it now before we get into the very wet season of the winter," Cardinal said.

But McBain has a hard time believing there are no other options and would like to see the community consulted about what happens to the beavers.

"Humans are impacting the environment, it's not beavers that are impacting the environment. We destroyed their habitat first, now we're just going to destroy them," she said.

With files from Deborah Goble