The Green Climate Fund (GCF) could begin offering results-based payments for protecting and restoring tropical forests as early as July. That’s good news for developing countries, where tropical deforestation can be nearly half of low-cost emission reductions. Yet funding to protect forests remains low and slow, as Frances Seymour and I explain in our book, Why Forests? Why Now? As the GCF moves to enable results-based payments for forests, earlier initiatives offer valuable lessons on two things the GCF should—and can—get right: 1) keep rules simple, and 2) recognize that institutional procedures built for upfront investments may not always be appropriate for results-based payments.