Karl grew up in Canada, Saint Lucia and Costa Rica and studied geography, economics and commerce at the University of Toronto. As a freelance journalist, he conducted interviews and reported from rainforests around the world. He won a full scholarship to study at Merton College, Oxford, where he completed graduate degrees in forestry, anthropology and agricultural economics and wrote for Private Eye magazine.

At the International Institute for Sustainable Development, he helped track new thinking on environment and development issues and edited a wide range of publications. As head of the Institute’s work on forests, he attended UN meetings and World Commission on Forests and Sustainable Development hearings and helped the Commission write its final report, Our Forests, Our Future, for Cambridge University Press.

As executive director of the Trust for Sustainable Living, Karl has helped transform the Living Rainforest centre into an international sustainability education charity and secure major grants from the Millennium Commission and European Commission. He founded the annual TSL International Schools Essay Competition and Debate and co-founded the Eco Attractions Group with other leading centres. Karl currently co-chairs the UN Voices of Future Generations project and sits on the Members Council of the Oxford Centre for Tropical Forests.