Were you under the impression that swans are an elegant and desirable part of nature? You might want to think again.

According to New York State, mute swans (the pretty white ones) are an alien invading species there and should be eradicated - all of them - within about 15 years. A menace, that's what they are, critics say. Even the beauties of Central Park wouldn't be safe, according to Hugh Raffles, professor of anthropology and liberal studies at The New School For Social Research in New York.

"There's an agreement on how wild animals can be euthanized, and that includes pretty much any strategy for killing an animal that you can think of – gassing, decapitation, whatever," says Raffles.

At the crux of the debate is the definition of an alien invading species: A species that arrives on our shores and thrives.

Asian carp

Silver carp, also known as Asian Carp, jump out of the water near the retention area off of the Wabash River in West Lafayette, Ind. (Michael Heinz/AP)

There's an emerging sub-set of science that has as its foundation the idea that alien biological species - plants and animals from somewhere else - are endangering our native land. They are undesirable, or at least 'persons of interest.'

The zebra mussel, the cane toad, killer bees, kudzu vine, the walking catfish and, right now, the flying Asian carp have all had their moment as the celebrity alien invading species du jour.

They eat our native species – plant and animal - as well as the food that's meant for the natives (at least according to human thinking). They are beyond our control and cost us money. They change the world around us and alter the landscapes of our childhood.

Government agencies even go so far as to make up wanted posters as part of campaigns to get the public to support eradication efforts. There are posters of unwanted fish, for example, wearing bandits’ masks and – inaccurately – showing fangs, according to Matthew Chew, assistant research professor at the Arizona State University School of Life Sciences. 

April 1 on Ideas

Listen to Barbara Nichol's full audio documentary Bioinvasion: Attack of the alien species! on CBC radio's Ideas at 9 p.m. EDT (9:30 p.m. NT). The documentary examines the phenomenon of invasive species and is a story as much about human nature as about nature. 

But there’s a divide within the new science of bioinvasion. A growing contingent within the scientific community believes the concentration of the changes wrought by alien species is off-target – that they are not somehow “worse” than the native species. It's a belief held by Ken Thompson, author of the recently published Where Do Camels Belong?: The story and science of invasive species.

And there are fascinating questions still not decided by the science of bioinvasion.

For example, the movements of plants and animals are nothing new. Camels, very surprisingly, are actually native to North America. Hippos and lions and alligators once made their homes in Great Britain. Species have shifted around since the long-ago days when the Earth had just one continent –Pangaea – although globalization (our doing) has accelerated species’ movement very greatly.

Human element

So what is an alien species?

And there’s a matter that we human beings don’t much consider: we can indict the zebra mussel and the Burmese python as alien invasive species, but we don’t acknowledge that we are the most damaging alien invasive species of all, according to Daniel Simberloff, senior editor of the Encyclopedia of Biological Invasions and author of Invasive Species: What Everyone Needs To Know.

Mute swan

A Mute Swan lands at the Titicus Reservoir in Purdys, New York. The latest move to eradicate invasive species has put the regal Mute Swan in sharpshooter's sites, but bird lovers from New York to Michigan are filling petitions to call off the proposed mass slaughter while the killing picks up speed in other states. (Eduardo Munoz/Reuters)

We don’t appear on the World Conservation Union’s famous “World’s Worst 100 Invading Species” list. Why not? Perhaps that would imply that we are nothing special, just one biological type among the many. And we like to shift the blame, that seems to be in our nature.

So, some are questioning whether the claims made against our most famous alien invading species are quite fair. Are we blaming the messengers, with our wanted posters and tall tales about the species’ we take after?

Yes, says Arizona State University's Chew. But change is hard for homo sapiens to accept, he points out.

"As Charles Elton said in his book The Ecology of Invasions by Animals and Plants, 'when I was a child, tigers lived in India and wallabies lived in Australia.'"

In fact, we are prone to suspecting immigrating humans as the cause of our troubles as well, in unsettling eras of change such as this. We're animals too, lest we forget, and our natures will lead us off the path of strict fairness and accuracy ... it's human nature.

As for the swans, while there are people who want them eradicated, there are also humans out there right now who are trying to plead their case in New York State.

[Listen to Barbara Nichol's full audio documentary Bioinvasion: Attack of the alien species! on CBC radio's Ideas at 9 p.m. EDT (9:30 p.m. NT). The documentary examines the phenomenon of invasive species and is a story as much about human nature as about nature.]