Alexander Von Humboldt - the forgotten father of environmentalism - warned of harmful human induced climate change over 200 years ago.
Explorer, nature writer and scientist he climbed the world’s highest volcanoes and delved deep into the rainforests devising his radical new ideas of nature in flux. Darwin set sail on the Beagle because of Humboldt’s books.
Roland Pease talks to author Andrea Wulf, who has retraced the footsteps of this remarkable lost hero of science.

Photo credit: Wellcome Library, London