History offers many instances of the importance of ecological processes. Humans have made major changes in their environments. They have had to adapt to the changes they made, by altering the patterns of their societies, or to disappear. This has happened in every historical period and in every part of the inhabited Earth.
I saw a many-faceted example of this in the volcanic island of Madeira, which rises in the Atlantic Ocean 1,200 km (750 mi) southwest of Lisbon and 765 km (475 mi) off the African coast. It is a spectacular island; its peak reaches 1,861m (6,106 ft), and on the northern coast, the swells from the open ocean often produce a thundering surf. Madeira was uninhabited until 1425, when João Gonçalves Zarco founded a Portuguese settlement under Prince Henry the Navigator. 1 At the time, most of the island was covered by the laurissilva, a thick forest of native laurel trees. 2 It was this forest that gave occasion to the island’s name: Madeira, the Wooded Isle. There were no mammals except bats and the colonies of monk seals on the coast. 3 Birds, especially marine species, were plentiful; there were a few species of land birds that occurred only in Madeira. The numerous species of insects fascinated Charles Darwin when he read about them; he pointed out that a surprising proportion of them, in the relative safety of the island environment, were flightless or unusually large, or both. 4 The settlers began an attack on the forest, hewing down the trees for export and starting fires to clear land for agriculture; sugar cane 5 at first and then grapevines that yielded the famous Madeira wine. 6 A folk story says that the forests burnt continually for seven years. An unknown number of native species must have perished from the fires and forest removal. Many non-native species were introduced, some intentionally and some by accident. Fifteen years after settlement, colonists found that cattle had escaped, gone wild, and become so numerous that they could kill them with ease. 7 Along with goats, the cattle decimated the vegetation, further reducing the habitat for wildlife. Once introduced to the nearby island, Porto Santo, rabbits swarmed everywhere, eating everything and driving the human residents off the island for a time. Cats, mice, and rats destroyed birds that were not used to mammalian predators. The Madeira wood pigeon and possibly three flightless rails became extinct. 8 Plants alien to Madeira, from showy garden flowers to aggressive weeds (sometimes the same plant is both), were introduced by the hundreds. I visited some of the few remaining stands of the laurel forest, which are now protected, and was told by Henrique Costa Neves, the director of the National Park, that a major project of eradication has to be waged against invading species, particularly the bananilha (Malayan ginger), a plant, escaped from gardens, which forms thickets that choke out other plants, and has virtually taken over the Azores Islands in recent years. 9 On Madeira’s neighboring islet, Deserta Grande, a campaign in 1996 eradicated rabbits, and probably mice and goats as well, and both vegetation and native