Which endangered species should we save? Humans face tough choices about what lives and what dies

As humans increasingly choose the winners and losers of the animal kingdom, will the monarch butterfly make the cut or will it be left to die out?

A once-familiar sight in Canadian gardens, migrating monarchs are flying closer to extinction. The International Union for Conservation of Nature on Thursday declaredthe butterfly an endangered species.

The monarch's struggles are largely the result of pesticides destroying milkweed the only plant that monarch larvae eat and scientists warn the species could go extinct within the next 15 years if it doesn't get more human help to survive.

But for that, the monarch must compete against more than 41,000 other threatened species of animals, insects and plants. Many more species will join them as climate change, industry and other factors decimate their habitats.

That means humans will have to make an increasing number of tough decisions in future about what life forms we want to save, with limited resources to do so.

"[You'll] get in these arguments about: is this particular plant worth it? Is this particular butterfly showy enough, or is this particular slug something that we care about?" said Holly Doremus, an environmental law professor at the University of California at Berkeley. "And that ends up taking a lot of resources in and of itself."

WATCH | Migrating monarch butterflies are now an endangered species:

Monarch butterflies added to endangered species list

2 years ago

Duration 2:11

The International Union for the Conservation of Nature has added the migratory monarch butterfly to its list of endangered species.

Given the choice between a charming, loveable creature such as a brilliant butterfly, or a slimy slug, what would you pick?

"That's actually the biggest problem in my line of profession," said Frank Khler, a mollusc expert at the Australian Museum who is fighting to save the giant pink Mount Kaputar slug of which only several dozen remain, atop a single remote mountain seven hours northwest of Sydney.

"People always are easily convinced about fluffy, furry things that we can somehow relate to, that are cute We have many other threatened species and it's very difficult to raise awareness for their conservation."

To Khler and other advocates for slugs, snails and unphotogenicbrown creatures, it's an ongoing fight to prove their organism of choice is as worthy of saving as any other.

"If things have a usefor humans, and are more attractive or more interesting, then of course we tend to level them a bit higher and I think that's probably a mistake," he said.

Survival of the worthiest?

In 1859, Charles Darwin's theory of natural selection changed the way humans understand animals' unique attributes, as well as explaining why some species thrive while others die out: the survival of the fittest.

But humans have always had a hand in picking the winners and losers of the animal kingdom, based on whether they're tasty, cute or useful.

Case in point: giant pandas, which struggle to reproduce, subsist on a single food that gives them barely any energy, and serve no obvious purpose aside from entertaining humans by tumbling comedicallyout of trees all of which only makes us more determined to save them.

"They are really cute," Doremus said.

"And that's the thing, right? We're saving them because they're so cute."

Few scientists will argue publicly against saving endangered species. In a 2017 opinion piece, R. Alexander Pyron, an associate professor of biology at George Washington University, espoused that conservation was a waste of time one which "serves to discharge our own guilt, but little else."

The piece drew a strong rebuttal from scientists and Nobel laureates, who wrote in a letter to the editor, "It is dangerous to think that we are 'no better or worse' without a large proportion of the species alive today."

After being publicly shamed for his opinion, Pyron subsequently backpedalled. (He declined an interview request from CBC News.)

Pyron was correct that extinction is an eventuality for every living species; however, humans are dramatically speeding along that process for many of them.

"It's like we're pruning the evolutionary tree of life," said Sally Otto, an evolutionary biologist and professor at the University of British Columbia.

"We're not losing things randomly we're losing, specifically, species that can't thrive alongside humans. Winners in this are going to be things like rats, and starlings, and pigeons, that can thrive in urban environments in crowded cities."

Picking winners and losers

In deciding how heavily to invest in saving any species, governments around the world use various criteria: the species' uniqueness, its likelihood of recovery, the fiscal cost, and what benefits it would bring.

In Canada, an independent advisory body assesses whether species should be regarded as endangered, but the federal government makes the final decision and it's not always based entirely on science.

"[This] can influence which species receive formal protection and, more broadly, the effectiveness of efforts to conserve biodiversity,"a group of American and Canadian scientists wrote in 2013.

In an email to CBC News, Environment Canada says the agencydeveloped a "Pan-Canadian approach" with provincial and territorial partners in 2018 to identifyanimals in need of conservation. It identifiedsix "priority species."

Those species are:

• Barren-ground caribou.
• Boreal caribou.
• Greater sage-grouse.
• Peary caribou.
• Southern mountain caribou.
• Wood bison.

"These species were chosen following a number of criteria and considerations in collaboration provincial and territorial partners," the agency said. "These include, but were not limited to, the species' role and value within their ecosystems, their conservation status and achievability of conservation outcomes, their social and cultural value (particularly to Indigenous peoples), and the leadership/partnership opportunities that their conservation presents."

Some scientists aren't keen on the government's criteria and broader approach. "We're not choosing in any rational way," Otto said. "We're losing species and not really deciding whether or not that's something we as a society want to happen or not."

The case for the monarch and everything else

Canadian advocates for the monarch argue the butterfly is more than just a pretty face and its utility is one more reason to save it.

"It's a pollinator [and] we need pollinators to survive we cannot eat fruit and vegetables if there's no pollinators," said Alessandro Dieni, an ecologist and co-ordinator of the Insectarium de Montral's Mission Monarch, a community science program.

But what about the thousands of life forms that are lacking in looks or obvious function? Should we bother saving them?

"Every species has its place in the ecosystem, and nature is so complex we don't even know often until a species is lost what kind of ramifications that will have down the line," said Sam Knight, a monarch expert at the Nature Conservancy of Canada, which focuses its work on protecting ecosystems, rather than individual species.

If the last surviving giant pink slugs were to die, Khler concedes their delicate ecosystem would in all likelihood be just fine without them.

But he cautions that humans shouldn't choose extinction for them on that basis alone.

"The question is: if you have a puzzle, how many pieces can you lose until you basically miss the whole picture?"

How you can help the monarch butterfly

Canadians can help by observing monarch butterflies in their community and monitoring milkweed during the International Monarch Monitoring Blitz from July 29 to Aug. 7.

People can also help by planting milkweed, or leaving it be, for monarchs to lay their eggs on, and avoiding using pesticides that might kill the weed or the insects that rely on it. As milkweed is considered a noxious weed, there are rules around which species of it can grow in different parts of Canada.