John Todd (born 1939) is a Canadian biologist working in the general field of ecological design. He addresses problems of food production and wastewater processing by using ecosystems technologies that incorporate plants, animals and bacteria. Todd has developed "Arks" or "bioshelters", ecologically closed "life-support systems" with the goal of sustainable functioning. He combines alternative technologies for renewable energy, organic farming, aquaculture, hydroponics and architecture to create "living machines"or "eco-machines".