Twenty years ago this month, Brazil helped globalize the environmental movement by hosting an Earth Summit, cast against the backdrop of its vanishing Amazon rain forest. It was "a historic moment for humanity," U.N. environment chief Maurice Strong said at the time, raising hopes that world leaders really could solve big environmental problems like climate change, deforestation or whaling.

After two decades of fits and starts, though, international progress has stalled on several of these fronts, perhaps most notably U.N. climate talks. Any afterglow from the 1992 Earth Summit faded years ago, leaving the environmental community with little reason for optimism. Yet despite the bleak outlook, an array of activists, entrepreneurs, diplomats and dignitaries are back in Brazil this month, hoping to recapture some of the '92 magic and prove that environmental diplomacy isn't dead.

The reunion kicks off June 5 with the 40th annual World Environment Day, started in 1972 by the U.N. Environment Program to be "the biggest and most widely celebrated global day for positive environmental action." Brazil is the official WED host country this year, just as it was for the 20th WED in June 1992 — when it also hosted the Earth Summit in Rio de Janeiro. Not coincidentally, Brazil is hosting another big U.N. Earth Summit later this month, called "Rio+20."

Aside from boosting public interest in rain forests, the '92 Earth Summit set the stage for decades of environmental geopolitics, spawning the U.N. Framework Convention on Climate Change, the U.N. Convention on Biological Diversity and "Agenda 21," a broad plan for 21st-century sustainability. Brazil is an apt host for Earth Summit 2012 not only because it hosted the first one, but also because it's a microcosm of environmental politics over the last 20 years, illustrating how difficult — yet also how possible — it can be to balance ecological and economic priorities.

Brazil is one of the planet's fastest-growing economies, forming the "B" in "BRIC" nations (along with Russia, India and China) that are expected to dominate global markets in coming decades. The U.S. Census Bureau projects Brazil's population will swell to 222.6 million people by 2020 — an 8.2 percent increase in just eight years, compared with projected growth of 7.3 percent in the U.S. and 3.1 percent in China over the same span. Brazil's economy is currently ranked No. 7 worldwide, according to the U.S. State Department, and will likely climb to No. 5 within a few years, spurred by a flurry of preparations for the 2016 Summer Olympics in Rio de Janeiro.

Amazon deforestation per year, 1988-2011

Despite all its economic success since the last Earth Summit, Brazil has also made progress in containing its biggest environmental problem: deforestation. The Amazon lost an average of 7,900 square miles annually from 1995 to 2005 — mainly due to clear-cutting for cattle ranching, logging and agriculture — but then lost only 3,800 square miles per year from 2006 to 2011. The rate of deforestation has fallen nearly 80 percent since 2004 (see chart above), even as Brazil's economy grew by about 40 percent. For a country where economic growth was once deeply linked to deforestation, this has been a welcome paradigm shift.

Much like the '92 Earth Summit, though, Brazil's environmental progress hasn't always lived up to expectations. The planned Belo Monte hydroelectric dam, for example, is slated to destroy swaths of forest cover and biodiversity, angering indigenous leaders as well as local and international environmentalists. Brazil also ranks 14th globally in carbon dioxide emissions — ahead of Australia, Indonesia and Italy — with about 75 percent of its CO2 coming directly from deforestation, thanks to burning vegetation and rotting trees. And even though deforestation rates are down, murders of environmental activists are still common in parts of the Amazon.

OUT TO PASTURE: Cattle ranchers, soy farmers and loggers often clear tracts of Amazon forest like this one, pictured in northern Brazil in 2005. (Photo: Antonio Scorza/AFP)

And now, as Brazil welcomes the spotlight of World Environment Day and Earth Summit 2012, its government is wrestling with legislation that critics say could wipe away much of its success in the Amazon. Brazil's Congress passed a forestry bill in April, under pressure from the agriculture industry, that would grant amnesty for illegal land-clearing and weaken a raft of environmental regulations. Among other changes, the bill would allow more deforestation near rivers, reduce protections for trees on sloped land, and let Amazon landowners meet forest-cover requirements by counting exotic trees like oil palm or wooded land they own elsewhere.

This opened deep divisons in Brazil over how to protect the Amazon, where many "ruralists" resent what they see as outsiders trying to stunt their economic growth. But it also sparked an upswell of environmentalists urging President Dilma Rousseff to veto the forestry bill, a campaign that only partly worked late last month. Rousseff used a line-item veto on May 25 to kill 12 of the bill's most unpopular provisions, calming some backlash but not nearly ending the broader debate.

"Legislation published today reversed and worsened the 1965 Forest Code, reduced the protection of Brazilian natural heritage, gave amnesty to illegal loggers, stimulated more deforestation with impunity and removed incentives for the restoration of Areas for Permanent Preservation," the World Wildlife Fund said in a statement May 28.

As reported this week, the Brazilian Academy of Sciences and Brazilian Society for the Advancement of Science had tried to delay the bill until a compromise could be reached, but those efforts fell through. "We proposed a moratorium of two years to study the issue," says University of São Paulo ecologist Luiz Martinelli. "Now we are in the middle of this mess, and I don't think it is going to end soon." Brazil's Congress has three months to overturn the vetoes, and an executive order patching up gaps in Rousseff's vetoed bill will expire if lawmakers don't approve it by August.

The official theme for this year's World Environment Day is "Green Economy: Does it include YOU?," a slogan that's meant to make a green economy seem more accessible. It's co-branded with the U.N. Environment Program's Green Economy Initiative, all part of a push to close the conceptual divide between economics and ecology. And while it isn't very catchy, it is a fitting theme for Brazil — a country whose rain forests seem to inspire environmental optimism that is catchy, both locally and abroad.

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Russell McLendon ( @russmclendon ) writes about humans and other wildlife.

Back to Brazil for World Environment Day
Forty years after the first World Environment Day, and 20 years after the original 'Earth Summit,' Brazil is still a flashpoint for environmental politics.