Rainforests are the lungs of our planet – regulators of the Earth's temperature and weather. They are also home to 50 per cent of the world's animals and plants – which for centuries have been the source of many of our key medicines. And yet we’ve all heard of their systematic destruction; the razing of trees to make way for cattle or plantations of oil palms, the disenfranchisement of indigenous peoples, and the corruption that leads to illegal logging and pollution. But the great environmentalist tells the other, inspirational story we’ve almost never heard: what is being done, and can be done in future, to protect the forests and the 1.6 billion people who depend upon them.