UN climate talks concluded in Cancun over the weekend without a major agreement to cut greenhouse gas emissions. But negotiators inched ahead on some fronts. One of them was the idea of keeping carbon out of the atmosphere--by keeping forests intact. That's a trail that California has been blazing with its own international partners.

In the tropical forest outside the tiny Mexican village of San Antonio Tuk, a Mayan man hacks shallow cuts into the bark of a towering gum tree. The villagers harvest the sap that oozes from the cuts, the natural latex used to make chewing gum.

Much of the village's income, however, comes from the Mexican government. The villagers are being paid to protect this forest, which lies five hours south of Cancun, in one of Mexico's most deforested regions.

"It's important to take care of the forest, not only for the money, but for our people and our future," said local head of the project, Miguel Cante Chuc, through an interpreter.

This project is part of something called "REDD," or "REDD-plus," which stands for Reducing Emissions from Deforestation and forest Degradation. It was one of the hottest topics at the UN climate talks in Cancun because deforestation accounts for about 15% of global greenhouse gas emissions.

Ban Ki Moon, the Secretary General of the United Nations, told a crowd gathered during the UN climate talks in Cancun that he is hopeful about REDD.

"REDD plus has great potential to protect the forests and spark creation of low-carbon initiatives around the world," he said.

The details of an international agreement on REDD still need to be worked out, but in essence REDD means paying developing nations not to cut down their forests. This way, developed nations can help reduce global emissions -- just not at home. They'd be paying poorer nations to reduce their emissions. And that's got some people concerned.

At a protest in Cancun a few miles from the UN climate talks that drew hundreds of people, protesters chanted, "No REDD," as they marched through the streets. "The problem with REDD is that it doesn't take into account indigenous rights," said actress Darryl Hannah, who attended one of the protests against REDD in Cancun during the UN summit.

"These communities that actually live in the forest, that have been the caretakers of those territories for ages are not really being taken into account."

Opponents also argue that REDD would allow developed countries and corporations to keep polluting.

Right now, the money for pilot projects like the one in San Antonio Tuk comes from governments and foundations. But a new partnership between California and provinces in Mexico and Brazil is exploring a market-based system for REDD.

"We can't wait for an international deal," said Cal-EPA chief Linda Adams.

Under the current draft rules for California's cap-and-trade system, expected to launch in January of 2012, companies will be able to meet a small percentage of their emissions reductions targets with international offsets, like paying for forestry projects in Mexico.

"We want most of the reductions to happen in California because of the potential co-benefits, but we can't ignore what's going on in the rest of the world," said Adams.

Last month, in Davis at the Governors' Global Climate Summit, California announced an agreement to sit down with officials in Acre, Brazil and Chaipas, Mexico, to figure out how to work together to ensure REDD projects in those provinces would be up to California standards.

"In today's world there's not a lot of credibility about these international projects," said Mary Nichols, chair of California's Air Resources Board.

Nichols said a lot more needs to be done to ensure that these projects can be monitored, enforced, and verified, and that they'll be as good as any similar project in California, a process she says could take up to two years.

"California is really the only compliance market in the world right now that's willing to try to explore this," said William Boyd, a Colorado law professor who heads up the Governor's Climate and Forest Task Force, a coalition of 16 regions from around the world, that's aimed at finding ways to fund REDD projects.

He says that California's REDD program would barely make a dent in global deforestation, potentially offsetting around 0.1% percent of related emissions in the first few years (2-4 million tons of CO2 per year). But, he said, that's not the point.

"California is not going to solve the deforestation problem, but it sends a really important signal, and it it's proof of concept. It's really important in showing how this can be done," he said.

The Air Resources Board will vote on the state's cap and trade plans on Thursday.