TORONTO - David Suzuki, Canada's best-known environmentalist, has spent a generation encouraging Canadians to look after the environment, but it seems they have not been listening.

Goateed, soft-spoken and avuncular, Suzuki has built a devout following from 28 years narrating "The Nature of Things," a popular television series on the science of the natural world.

Now aged 71, he notes Canada's environmental credentials are eroding just when he says it is more important than ever to move in the opposite direction.

While Canada ratified the 1997 Kyoto Protocol on limiting greenhouse gas emissions, the current, Conservative government says the standards cannot be met, reopening a debate he thought had been won.

"We've already been here before, and that's the thing that breaks my heart," he told Reuters during one of his frequent trips to Toronto from his home in Vancouver.

"If we had taken it seriously and done something, we would be so far past the Kyoto target today, and the problems would be infinitely simpler and cheaper."

In the 1990s, "there was a sense that Canada was a good environmental citizen," he said. But data submitted to the United Nations shows that since 1990, the country's greenhouse gas emissions have risen more than in any other leading industrialized nation.

"Canada has coasted on a reputation far beyond its merits," Suzuki said.

Suzuki was born in Vancouver, British Columbia, as were his parents. His grandparents were Japanese. He studied zoology at the University of Chicago before returning to teach at the University of British Columbia.

He has written some 43 books. The latest, which he co-authored, is called "Tree: A Life Story."

His David Suzuki Foundation plays a role in Canada similar to that of organizations such as Greenpeace in other countries, drawing attention to green issues, providing scientific evidence, raising money and lobbying for support.

His criticism of polluters has made him enemies, especially among companies operating in Alberta's lucrative oil patch, and he has been derided as a "self-anointed prophet" in newspaper commentaries.

But the long battle to illuminate human impact on the environment is frustrating.

He points out that, although emission curbs could hurt Canada's energy and auto industries, climate change will hit others such as agriculture, forestry, fisheries and tourism.

"Canada, as a nation, is probably more vulnerable than any other country ... because we have the longest marine coastline on the planet," he said.

"When the ice sheets drop, you're going to get massive rises in sea levels."

He said the effect of climate change is evident and already even taken for granted in places like the Beaufort Sea, where arrived after rafting down the Firth River in Yukon Territory last summer.

A poll by the CBC in 2004 placed Suzuki as the fifth "Greatest Canadian," the highest ranking for a living candidate, behind such figures as Tommy Douglas, the father of Canada's system of public health care, and Pierre Trudeau, the youthful prime minister who captivated the country in the 1970s.

But it is his role as narrator of CBC's "The Nature of Things" that has earned him his greatest following. The program, which airs in several countries including the United States, often uses iconic images like polar bears to convey global warming to its mostly urban viewers.

He said working on the show has forced him to make sure everything he says outside the show is backed by science, especially on the occasions when his short fuse has caused him to "shoot off" his mouth.

"I had thought I was empowering people with information," he said of the TV series. "What happened, in fact, is that I was empowering me."