A U.S. federal proposal that could see B.C. grizzly bears captured and shipped south to Washington State has drawn such a huge response, the public comment period has been extended for more than a month.

More than 100,000 people have weighed in on the proposal to reintroduce grizzly bears to the North Cascades ecosystem in Washington State, said the National Parks Service.

That number has seen a huge boost in the past week, due to an online campaign by the popular Seattle cartoonist Matthew Inman, better known as The Oatmeal, who supports the plan to move grizzlies.

I have a favor to ask. <a href="https://t.co/qrkHnLEtUU">https://t.co/qrkHnLEtUU</a> <a href="https://t.co/vdTjI26bul">pic.twitter.com/vdTjI26bul</a> —@Oatmeal

The North Cascades once had thousands of grizzly bears but now there are fewer than 10 — and there hasn't been a confirmed sighting on the U.S. side of the border since 1996.

The proposal would see grizzly bears captured and flown in from healthy source populations in either Montana or British Columbia, which has an estimated quarter of all the grizzly bears in North America.

"Because it's happening in a national park and because grizzly bears are something that people are passionate about [on both sides] ... it's not surprising that we have a large number of comments," said Denise Schultz of the North Cascades National Park Service.

The grizzly bear population in the North Cascades in the U.S. has fewer than 10 individuals and no confirmed sightings since 1996. (U.S. National Park Service)

'Canadian bear posses' to the rescue?

Bears, of course, don't check in at customs when they cross the border — but the challenge for the North Cascades is the nearby B.C. population is also threatened.

"There aren't any Canadian bear posses coming to the rescue" without human intervention, said Joe Scott of Conservation Northwest, a Washington-based environmental group that's been working on the issue for decades.

"It's clear that grizzly bears are not going to come back on their own to the Cascades."

The North Cascades bear population was pushed to near-extinction by hunting and other human activity, but the area still has ample remote wilderness habitat to support a population of about 200 grizzlies, according to the U.S. federal assessment.

The National Park Service and U.S. Fish and Wildlife service has put forward a draft plan with four options to restore the North Cascades bear population, which range from taking no action to moving 200 grizzlies within the next 25 years.

Conservation Northwest, the National Wildlife Federation, and The Oatmeal are supporting what Scott calls a "modest proposal," to move 25 bears over the next five to 10 years, then monitor those bears and see how they do.

"Grizzly bears are a wilderness icon. They have enormous benefits for ecosystems … and they're essentially a missing piece here."

A grizzly bear roams near Beaver Lake in Yellowstone National Park, Wyo. Grizzly bears once roamed the rugged landscape of the North Cascades in Washington state but few have been sighted in recent decades. (Jim Urquhart/Associated Press)

Border-crossing bears?

Moving bears is not an easy task — and not just in the ways you might think.

The grizzlies have to come from a source group that eats the same kinds of food as the landlocked North Cascades and is a stable enough population to survive the removal of young bears from the breeding population.

The bears would be captured in baited traps, then transported, being deposited by helicopter to their final remote destinations.

The Wells Gray area of central B.C., which had 317 grizzlies in 2012, has been identified as a possible source population, along with a larger one in northwest Montana.

"We know that those populations can afford to contribute a couple of bears over several years," said Scott.

"It's a good thing for the species and we believe that our Canadian friends who live around Wells Gray would be happy to help us with that effort."

Coastal bears, like this grizzly on B.C.'s Central Coast, wouldn't be a good fit to reintroduce to the landlocked North Cascades, said the National Park Service. (Chris Darimont/University of Victoria)

The B.C. Ministry of Environment declined a request from CBC News to discuss the grizzly plan, but in a statement said it will discuss the idea after the U.S. government decides what it plans to do, likely in early 2018.

"Once that decision is made, B.C. will work with our U.S. colleagues to further define B.C.'s level of engagement," the statement read.

Schultz of the National Park Service confirmed there is no agreement in place to move B.C. bears.

"There will be a lot of conversation and negotiation and I'm sure paperwork that's going to need to happen, if in fact, that's the end result of this."

The public comment period is open until April 28, and comments from Canadians are welcome, said Schultz.