Forests and the ocean are vital for climate, biological diversity, and human communities, but they are degraded and their ecosystem services are seriously impaired, mainly because financial, economic and governance structures are misconfigured. We propose that G20 help strengthen the REDD+ climate instrument for forests and extend it to Blue Carbon1 from coastal and marine ecosystems. Scaled up to cover the Earth’s two largest, most diverse and most productive ecosystems, these two approaches can deliver significant economic and climate benefits.