Slash and burn farming is an environmental catastrophe on the rise. Around 250million domestic tropical farmers use the technique that gives a year's fertile soil, which then washes away with the next year's rains, perpetually forcing growers into fresh rainforest. Deforestation accounts for more carbon emissions than all international transport, and slash-and-burn accounts for around half of that. But there is an answer. Cornish scientist Mike Hands has been working with a sustainable solution in Honduras for the past 20 years. We follow his struggle to break the devastating cycle and challenge international agricultural agencies.