It is often promoted as the most promising solution to deforestation. Under the scheme, known as Reducing Emissions from Deforestation and Forest Degradation (REDD+), the owners of power plants, industrial facilities and other sources of greenhouse-gas emissions finance forest-conservation projects, offsetting their emissions in the process. The money goes to indigenous and other rainforest peoples as payment for preserving the woodlands. And deforestation, which is responsible for around 18% of global greenhouse-gas emissions and ever-escalating destruction of plant and animal species, eases to the great benefit of the planet.

That, at least, is the idea. The reality is that although policy makers first discussed the concept in the mid-1990s, REDD+ still finds itself struggling to gain traction. The long-sought global compliance market that would incorporate the scheme and yield billions for forest conservation in Latin America and other developing regions is unlikely to be functioning before the end of the decade, hostage to the slow-moving negotiations over a new United Nations climate treaty. Europe’s Emissions Trading Scheme, the world’s largest compliance market, prohibits the use of REDD+ credits, partly due to difficulties in measuring and ensuring carbon capture in forests.

For a time, REDD+ supporters hoped California’s carbon cap-and-trade program would help brighten the forest-conservation strategy’s prospects. But even in California, the problems have been numerous. Under California’s system, which began Jan. 1 and seeks to reduce the state’s greenhouse-gas emissions to 1990 levels by 2020, polluters might eventually be able to use international forestry projects to offset up to 4% of their carbon emissions. California has signed memoranda of understanding with the Brazilian state of Acre and the Mexican state of Chiapas as a first step toward importing REDD+ credits from those regions. Supporters see the projects as a test case for other nations and states interested in creating similar systems, including Australia, Japan and New Zealand, where use of REDD+ offsets is widely discussed.

Yet with California wrestling over whether—and, if so, how—to incorporate Acre and Chiapas into its carbon market, the idea of using REDD+ has drawn an outpouring of protest. As in Europe, dissenters in the United States and Latin America worry that there are few guarantees REDD+ will result in real carbon reductions. They argue that because Latin American forest communities typically lack land titles and have little say in whether projects take place, REDD+ is inherently risky. They also contend REDD+ could prompt business interests to seize land to tap carbon-trading profits, preventing traditional communities from using forests, as they long have, for hunting, fishing and sustainable agriculture and forestry.

Letters to Gov. Brown

REDD+ can end up criminalizing traditional practices “through which forest communities have historically coexisted with, managed and preserved the forests,” says a letter that more than two dozen Acre indigenous, environmental and human rights groups sent to California Governor Jerry Brown. Similar letters by dozens of groups in Chiapas and the United States, including Friends of the Earth, Greenpeace International and Sierra Club California were sent in April and May, asking the governor to reject international REDD+ projects as part of California’s carbon market.

The crucial decision on whether to accept international offsets will be made by the California Air Resources Board (ARB), which has oversight over the cap-and-trade system. But that decision will not be made until October at the earliest, experts say. If the board votes in favor, California probably will then take several months more to establish REDD+ rules and regulations, and Acre and Chiapas will need a period of time after that in which to adjust their regimens to California’s.

Critics of including foreign projects in California’s greenhouse-gas regimen warn of poor outcomes. Including them “may result in projects that both fail to reduce carbon and affect forest communities,” says Brian Nowicki of the nonprofit Center for Biological Diversity, which signed the letter from U.S. groups. In extreme cases, he adds, alliances between local governments and business groups trying to profit from REDD+ “could result in displacement of forest communities.”

Some indigenous people support REDD+ as a way to save forests and preserve traditional ways of life. But in February, the National Coordinating Body of Indigenous Peoples in Panama, representing the nation’s seven main indigenous groups, withdrew from a United Nations program that uses pilot projects in the jungles to prepare the country for a global REDD+ system. The indigenous groups in Panama, like those in Acre and Chiapas, complain they’ve had no input in designing the endeavors.

Defenders undeterred

The intense resistance to REDD+ from some quarters has disappointed California planners, who say that in Chiapas and Acre, local governments have tried to involve all sectors of society in developing Redd+ programs. They also say that Acre and Chiapas have made a commitment to measure emissions reductions on a statewide basis, rather than project by project. This would help ensure that forest conservation in one part of a state doesn’t lead to increased deforestation in others.

Acre, often cited as a model for REDD+ because of its extensive planning, has strict zoning protections as well as incentives and payments for environmental services. Those policies, as measured in 2003-07, have promoted wiser use of the land, helping to boost agricultural value in the state while reducing deforestation by 80%. Still overwhelmingly forested, Acre “is the most advanced REDD jurisdiction in the world [at any level of governance],” according to the REDD Offset Working Group (ROW), a voluntary board of mostly technical experts which advises the California program. “Acre is committed to building a comprehensive jurisdictional program for low-emissions development, and the California opportunity is an important part of that,” says William Boyd, a law professor at the University of Colorado and a co-author of the ROW report.

REDD+ supporters have not abandoned hope. They say that while incorporating REDD+ offsets into the California system might face hurdles and take years, it represents the most promising way to create a powerful economic incentive for forest conservation.