If tropical forests are to be protected, these kinds of financial incentives are imperative. Why? Consider the reality of the land market in the Amazon: An acre of cleared land is worth far more than an acre of forest. This means that farms that are mostly forested, as required by the law, are worth far less than farms that are mostly cleared. Forest-conserving farmers who are helping slow climate change because of the large amount of carbon contained in forest trees receive nothing in return.

This market reality has given an unfair advantage to farmers and land grabbers who succeed in avoiding law enforcement efforts to stop deforestation. They simply cut and burn large tracts of the forest illegally to grow crops or raise cattle, or to make a claim of ownership by showing productive use of the land.

Financial incentives could spur farmers to conserve more forest on their farms and to start reforesting along rivers and streams ahead of a 2040 deadline to do so.

This is where the California tropical forest standard comes in. It offers the potential for changing the incentives. The retailer Amazon, commercial airlines and dozens of other companies that are making similar pledges to climate neutrality could, through their purchase of carbon offsets, inject money into the tropical regions that are building their economies while protecting forests and recognizing the rights of indigenous peoples.

And if the online retailer is just the beginning of a much larger corporate wave, the demand for these offsets, delivered according to the rules established by the California standard, could grow rapidly. In addition, other states or nations with carbon cap-and-trade programs, including the Canadian provinces and perhaps even China, should be encouraged to adopt the California standard.

Developing clear rules to govern these financial transactions was one of the goals of a recent United Nations climate summit in Madrid but was not completed. Among the issues unresolved, for instance, was this: If an American company achieves voluntary climate neutrality in part by investing in a Brazilian program that is reducing emissions by curtailing deforestation in the Amazon, is Brazil still able to claim those emission reductions as progress toward its commitment under the Paris climate agreement to reduce greenhouse gas pollution?

But even before this standard is activated, provincial and local governments in Brazil and other countries urgently need investors and technical support now to slow deforestation.