June 11, 2012

ONE OF THE GREATEST weapons against climate change sits on vast tracts of undeveloped Brazilian land. The country is home to nearly half of Earth’s rainforests, gobbling up 2 billion tons of carbon dioxide every year — a third of the United States’ 2010 greenhouse gas output. Maintaining, and expanding, what the Economist aptly termed “the world’s lungs” will be essential to fighting global warming, not to mention preserving biological diversity and water systems.

The good news: With the help of satellite monitoring and other tools, Brazil last year slowed illegal deforestation to a fifth of its peak in 1995, when the country lost a whopping 29,000 square kilometers of its rainforest to unauthorized slashing. The bad news: Brazil’s government is weakening its landmark Forest Code, the legal basis for that improved enforcement.

Rural interests in the Brazilian legislature pressed revisions to the Forest Code that would have granted amnesty to those who engaged in illegal deforestation before 2008 and drastically reduced the amount of rainforest landowners are required to preserve. Brazil’s Institute for Applied Economic Research estimated that the “ruralista” bloc’s code would have resulted in the loss of 190 million precious acres. Despite a prominent environmentalist campaign, Brazilian President Dilma Rousseff last month vetoed only a few of the most troubling revisions, softening preservation mandates.

Environmentalists argue that there is already plenty of cleared, arable land available in Brazil, and that the goal should be to grow more on it. Yet it is difficult for individuals to profit from holding unused forested plots, and there is economic opportunity in expanding production of Brazilian commodities, such as soybeans and orange juice, to feed the world’s growing population. In other words, it’s hard to preserve forests when international markets do not value them.

World governments must change that. Instead of expecting Brazil and other countries to bear all the costs of preserving ecologically valuable land, fairness and efficiency argue for an international program to turn forest preservation into a source of income. In its most efficient form, the money to pay for saving forests would come from an international carbon market, not from strapped national treasuries. But gridlock in international climate talks, mostly relating to issues other than deforestation, has made progress on creating such a program unacceptably slow.

For now, a “voluntary” market exists to serve environmentally minded corporations and individuals who would like to offset their carbon-producing activities by financing forest preservation. As states, provinces and nations ramp up cap-and-trade carbon-pricing schemes, there is opportunity to hook forest preservation into them, too. But deforestation, in Brazil and elsewhere, is a massive problem, much larger than the meager amounts spent to address it so far.

Brazil’s legislature, which may act following Ms. Rousseff’s partial veto, should reconsider its new forest code. But the international community, led by the United States, must also give developing nations more incentive to preserve their ecological wealth.