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From moose to wolverines, animals are interwoven into the Canadian consciousness. A walk through many of our cities reveals buildings whose decorative medallions salute our iconic species. The beaver, whose pelts drew Europeans to the New World, is on our nickel. The caribou graces our quarter. And everyone earns and spends the Loon.

Yet this vast diversity of species, like the rest of Canada's natural wealth, cannot be taken for granted. Since European settlers first arrived, hunting and dwindling habitat have increased the pressure on our fauna.

That being said, the past four centuries have not been a total catastrophe for Canada's native species.

Conservation has restored several threatened populations, including the marten, beaver, grey whale and Pacific sea otter, to health. Other species, like the coyote, have proved so resilient that problems with them -- especially in cities -- involve too many critters, not too few. At last report, Toronto's dominant species was probably the raccoon.

Still, threats to our animals persist -- some of them hidden. Only this spring, new scientific analyses revealed geographic "hot spots" where various species, not previously considered to be at risk, are in fact on the brink of endangerment.

While these hot spots range from Tasmania to Russia, the biggest "risk-of-risk" regions on Earth lie in Canada's Arctic and sub-Arctic. Animals such as caribou and musk ox, long believed to exist in such large numbers as to be unassailable, may be in a more precarious position than thought. How could these apparently robust species be at risk?

A paperpublished recently in the Proceedings of the U.S. National Academy of Sciences contained a latent-risk assessment that includes such factors as the animals' range, size, reproduction habits and maturation times.

Of all these variables, the most critical is an animal's size. "Conservation biologists have always known that large-bodied mammals are at greater risk of extinction," says Georgina Mace, one of the paper's authors.

"Now [that] we understand the mechanisms [of extinction], we are able to tailor conservation programs dependent on size," says Dr. Mace, of the Institute of Zoology, the research division of the Zoological Society of London.

For small mammals, the Canadian Sierra Club says, the best approach is to conserve habitat. "Without a home, species do not survive," it notes.

Yet even this motherhood statement has to be qualified, the Institute of Zoology cautions. "Large mammals . . . need a more complex conservation strategy, which takes into account their biology in combination with the external threats they face," the institute says in a recent news release.

Conservation biologists are still developing measures to keep risk-of-risk populations off the World Conservation Union's dreaded Red List of endangered species. Vertebrates make up 10 per cent of all animals sampled, including the white Siberian tiger and the saw-whet owl of British Columbia. By definition, these species face imminent extinction.

Suggestions to protect risk-of-risk animals include monitoring populations and covering them under national species-protection laws.

Yet the question must be asked: Why bother at all? Wouldn't it be simpler to wait until Canada's northern species creep onto the Red List before taking action to protect them?

No, says Thomas Brooks of the Center for Applied Biodiversity Science in Washington, D.C., one of the risk-assessment paper's scientific referees.

"Pro-active solutions are cheaper and easier," he says. "It's widely recognized among conservation practitioners that wherever we have the opportunity, we should get ahead of the curve and implement pro-active conservation measures."

The "curve" to which Dr. Brooks refers is an "extinction graph" that shows the yearly number of species extinctions around the world. If the same number of species died out every year, the graph would be a straight line. But its slope is steadily increasing -- and it is now as steep as a ski hill.

Unless it levels off, Earth's flora and fauna around 2100 will be perhaps a 10th of what they numbered circa 1800.

The rationale to intervene before a species emergency occurs comes as much from economics as from biology, says Andy Purvis, another author of the paper in Proceedings of the National Academy of Sciences.

"Latent-risk hot spots might provide cost-effective options for conservation," says Dr. Purvis, of the department of biological sciences at Britain's Imperial College. "They're places that are relatively intact. Preventing damage [there] is likely to be more effective than trying to repair it."

It seems that in conservation, as in other matters, a gram of prevention is worth a kilogram of cure.

When the first settlers reached North America, a small bird called the passenger pigeon existed in the hundreds of billions. Thunderclouds of them blotted out the sun for hours; biologists suspect that this bird was the single biggest single-species biomass on Earth, bigger than the Atlantic cod or the Douglas fir that still blankets the Coast Mountains of British Columbia.

Yet like the North American bison, a single herd of which might number 50 million in the 1700s, the passenger pigeon was decimated in a few decades.

Both species succumbed to a "perfect storm" of eradication pressures --- including loss of habitat to settlers' farms and efficient new hunting technologies, i.e. guns.

Only a century ago, a "Grand Pigeon Shooting Match" was advertised for a rural area outside a small Canadian city. The town was Toronto; the site was the corner of Yonge Street and Sheppard Avenue. After the shooting match, road potholes were filled with the passenger pigeons' corpses.

The Sierra Club suggests that a comprehensive law to protect risk-of-risk species should be called Martha's Law, after the last of the passenger pigeons that died in captivity a century ago.

Interestingly enough, there's nothing new in this. Anthropologists suspect that North America's aboriginal Pleistocene fauna, including woolly mammoths and giant sloths, were destroyed by a "killing front" of a new species invading across an Asian land bridge around 30,000 BC. The incursive species was Homo sapiens.

Back then, the killing technology was flints and not firearms, but the effect was the same.

Through the Global Convention on Biological Diversity, the international community has set itself the goal of making a substantial reduction in the rate of species loss by 2010.

However, according to the Millennium Ecosystem Assessment, an audit of Earth's ecological health published in 2005, extinctions still occur at up to 1,000 times the normal rate.

The authors of the MEA estimate that one-third of all amphibians, one-fifth of mammals and one-eighth of birds are now threatened with extinction.

They also conclude that although humanity is the cause, humanity will ultimately be among the losers. Reducing biodiversity, it says, will compromise fresh water, reduce useful bacteria and diminish economically valuable natural goods such as fish and timber. In fact, these processes have already begun.

"We need to keep an eye on species before they start declining to extinction," says Marcel Cardillo of Imperial College's department of biological sciences, the lead author of the National Academy of Sciences paper. "What [species] we think is safe now may soon go through a rapid decline. We shouldn't be too confident about the species around us."

William Illsey Atkinson is a frequent contributor to The Globe and Mail science page.