Solving our global climate crisis hinges on doing a number of things right. One is slowing - eventually stopping - deforestation, which now accounts for 15-20% of global greenhouse gas emissions. To do that we need to know how much stopping deforestation costs and where on the Earth's vast tropical belt it can be done most cost-effectively. With the support of the Gordon and Betty Moore Foundation, CSF is designing an "opportunity cost" analysis method that will work at the level of individual farms and be scalable up to the level of entire regions.