his scheme, were divided into those that were recently separated from a continent (like Britain) and those much less recently (like Madagascar). Wallace discussed how that difference affected flora and fauna. He discussed how isolation affected evolution and how that could result in the preservation of classes of animals, such as the lemurs of Madagascar that were remnants of once widespread continental faunas. He extensively discussed how changes of climate, particularly periods of increased glaciation, may have affected the distribution of flora and fauna on some islands, and the first portion of the book discusses possible causes of these great ice ages. Island Life was considered a very important work at the time of its publication. It was discussed extensively in scientific circles both in published reviews and in private correspondence. Environmentalism Wallace's extensive work in biogeography made him aware of the impact of human activities on the natural world. In Tropical Nature and Other Essays (1878), he warned about the dangers of deforestation and soil erosion, especially in tropical climates prone to heavy rainfall. Noting the complex interactions between vegetation and climate, he warned that the extensive clearing of rainforest for coffee cultivation in Ceylon (now called Sri Lanka) and India would adversely impact the climate in those countries and lead to their impoverishment due to soil erosion. In Island Life, Wallace again mentioned deforestation and invasive species. On the impact of European colonisation on the island of Saint Helena, he wrote that the island was "now so barren and forbidding that some persons find it difficult to believe that it was once all green and fertile". He explained that the soil was protected by the island's vegetation; once that was destroyed, the soil was washed off the steep slopes by heavy tropical rain, leaving "bare rock or sterile clay". He attributed the "irreparable destruction" to feral goats, introduced in 1513. The island's forests were further damaged by the "reckless waste" of the East India Company from 1651, which used the bark of valuable redwood and ebony trees for tanning, leaving the wood to rot unused. Wallace's comments on environment grew more urgent later in his career. In The World of Life (1911) he wrote that people should view nature "as invested with a certain sanctity, to be used by us but not abused, and never to be recklessly destroyed or defaced." Astrobiology Wallace's 1904 book Man's Place in