It is being billed as a "once in a generation" chance to design a blueprint for the Earth's future.

But negotiators at the UN Conference on Sustainable Development here in Rio de Janeiro are clearly struggling to live up to that billing. And in the process, Canada's environmental reputation is taking another beating.

As many as 50,000 people, including more than 130 world leaders, are descending on Rio this week for the summit known as Rio+20 — 20 years after the original Earth Summit was held in this city in 1992.

It was a heady time back then. World leaders agreed to tackle tough environmental challenges, including climate change and protection of the Earth's biodiversity, and Canada was leading the way.

Canadian conference chair Maurice Strong, then prime minister Brian Mulroney and environment minister Jean Charest were praised for brokering behind-the-scenes deals and setting the example for other nations to follow.

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A boy from the Paresi tribe slings a rock while playing in the Kari-Oca village, where indigenous groups are staying during Rio+20 conference in Brazil. (Felipe Dana / Associated Press)

Twenty years later, however, a different Canadian Conservative government is being singled out as a villain by many here. Even Quebec Premier Jean Charest has shown up to say Canada should be demonstrating more environmental leadership on the world stage.

As a resource economy, Canada felt compelled to show leadership back in 1992, Charest told reporters here in Rio, and out of pure self-interest, if nothing else, it should do the same now.

"If we don't make that demonstration to the rest of the world," he said, "we put ourselves in a position where we're vulnerable to markets, where the perception of our products can be criticized."

At the Rio conference, which begins officially on Wednesday, Canada is being accused of blocking a compromise deal on a number of high-profile issues, including phasing out subsidies for oil and gas exploration, and taking no initiative to help find agreement on the differing points of view.

Prime Minister Stephen Harper is not even coming to the summit. Though neither are U.S. President Barack Obama, German Chancellor Angela Merkel nor the U.K.'s David Cameron.

Still, more than 130 world leaders are expected, including France's new president, Francois Hollande, Russia's Vladimir Putin and China's Hu Jintao.

They arrive on Wednesday for three days of high-level negotiations. The U.S. delegation is being led by Secretary of State Hillary Clinton, Canada's by Environment Minister Peter Kent.

A different mindset

Quebec's Charest is back in Rio to talk about his government's plan to protect a chunk of the boreal forest the size of France, an initiative that has gained considerable international attention.

He told reporters here that, in 1992, the Canadian government had a completely different mindset on the environment.

As a northern country, he said, Canada felt it would be affected more than most by climate change, so if it wanted an international agreement it would have to lead by example.

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Quebec Premier Jean Charest, shown here giving a speech in Montreal earlier this month, is attending the UN summit on sustainable development in Rio. (Christinne Muschi / Reuters)

As the conference chair, businessman Maurice Strong had asked the Canadian government to help end the impasse in negotiations. "And we did," says Charest.

"Canada broke the logjam. We were the first to announce our decision to support the biodiversity convention, the climate change convention and we played a leadership role."

Charest calls it one of the defining moments of his political career. But today, 20 years later, the atmosphere in Rio is much less idealistic.

As a result of the high-profile failures of recent climate summits, such as at Copenhagen in 2009 and Durban last year (when Canada pulled out of the Kyoto accord), "negotiation fatigue" appears to have set in.

After years of failing to meet environmental targets, particularly on climate change and biodiversity, several countries are not committing themselves to any binding legal agreements here.

This summit is supposed to come up with a plan that will encourage economic growth and that doesn't devour the Earth's resources in the process.

But so far, at least, countries can't even agree on the meaning of the new catchphrase "green economy."

'Not efficient'

According to the latest World Wildlife Fund report, we need a planet-and-a-half to keep up with our current consumption rates, says Roberto Troya, the regional director for the WWF in Latin America and the Caribbean.

He also suggests that the bureaucratic UN may no longer be the place to deal with the urgency needed on environmental issues.

Listen to Quirks & Quarks interview with Green Party Leader Elizabeth May about the first Rio summit.

"In order to discuss just the title of a document, it takes several hours or days," he says. "That's not efficient. That's not what the world requires."

The WWF has singled out Canada on a couple of occasions here recently, putting it on its list of  "blockers," along with leading OPEC members such as the oil-producing nations of Venezuela, Saudi Arabia, Qatar and Ecuador.

In the preliminary talks, the WWF accused Canada of blocking the negotiating text that included a reference to "principles of basic sustainable development, protecting high seas biodiversity and a commitment to ending fossil fuel subsidies."

Its statement claims "Canada has blocked progress so far in every realm at Rio+20" and that it "seems unwilling to make any concessions.

"It’s not clear anyone from Canada has any mandate to move in any way on any issue," the WWF statement says. "Canada appears disinterested in measures to safeguard the environment."

Other academics and activists who are keeping a close watch on the climate and energy negotiations at this Earth Summit agree that Canada has been, as one said, "very problematic" when it comes to these UN negotiations.

In some cases, instead of blatantly blocking a paragraph in the official text, they say Canadian negotiators are creating loopholes or offering language that substantially weakens the text, such as "suggest we consider" instead of "we commit."

For its part, the Canadian delegation has been unusually quiet about its Earth Summit objectives, even after Britain's Guardian newspaper leaked what it said was a draft of the Canadian negotiating position on oil and gas subsidies. (The European Union wants a full phase-out of these subsidies; Canada reportedly is only willing to commit to "considering" eliminating them.)

But it is clear that Canada is saying an absolute no to an issue that is key to getting any agreement here: Developing nations, including the host Brazil, are pushing for a technology transfer fund that would help poorer countries switch to clean technology.

Observers say Canadian negotiators are blocking all wording that asks rich nations to commit any new financial resources to sustainable development initiatives.

The WWF's Troya, who also attended the original Rio summit 20 years ago, says there has been a 180-degree change in Canada's position.

"This is a Canada that doesn't speak to the Canada my colleagues and I saw in Rio in 1992."