1 Introduction History and ecology
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 1,861 m (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 Joao Concalves Zarco founded a Portuguese settlement under Prince Henry the Navigator.â At the time, most of the island was covered by the laurissilva, a thick forest of native laurel trees? It was this forest that gave occasion to the islandâs name: Madeira, the Wooded Isle. There were no mammals except bats and the colonies of monk seals on the coast.â 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 ï¬ight- less or unusually large, or both.â The settlers began an attack on the forest, hewing down the trees for export and starting ï¬res to clear land for agriculture: sugar cane5 at first and then grapevines that yielded the famous Madeira wine.â A folk story says that the forests burnt continually for seven years. An unknown number of native species must have per- ished 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.â Along with goats, the cattle decimated the vegetation, further reducing the habitat for wildlife. Once introduced to the nearby island, Porto Santo, rabbits swarmed every- where, 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 ï¬ightless rails became extinct.â Plants alien to Madeira. from showy garden ï¬owers 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.â On Madeiraâs neighboring islet, Deserta Grande, a campaign in 1996 eradicated rabbits, and probably mice and goats as well, and both vegetation and native
Figure 1.1 A landscape transformed by human actions. A native forest of laurel and other trees covered these mountain slopes on the north coast of Madeira Island before the ï¬fteenth century. Then Portuguese settlers arrived. constructed terraces, and planted vineyards whose grapes were used to produce the wellâknown Madeira wines. Photograph taken in 1999.
History and ecology 3
birds are making a remarkable ârecovery.â The outlying Selvagens. the least disturbed islands in the North Atlantic, are now protected by the Madeiran Park Service and are home to thriving sea bird colonies." But the native ecosystem of Madeira itself has been irreparably disrupted. At the beginning of an ecological history of the world. Madeira presents a question of scale. Madeira is a small island, only 57 km (35 mi) long and 22km (14mi) wide. The changes that take place there are local in scale, although they reï¬ect events worldwide in scope. such as the colonial expansion of Europeans and the introduction of non-native species to formerly isolated lands. To talk only about planetary processes in a history like this one would be too abstract. too generalized. To use only local examples would be to lose the major themes in a mass of detail. Therefore chapters in this book will contain both general narratives on a global scale and case studies on local and intermediate scales that illustrate the larger picture. Egypt provides an example of ecological processes on a regional scale. that of an immense river valley. For thousands of years the Nile rose annually in a ï¬ood that watered and renewed the land. depositing a layer of rich sediment. Then in the mid-twentieth century. a high dam constructed at Aswan ended the ï¬ooding. The structure itself. which I have seen from the river and from the air, is intimidating, more vast than the pyramids. but its effects on the land and people were even more enonnous. Nubians who lived in the area of the new reservoir had to move elsewhere. and Egyptian farmers modiï¬ed their systems of cropping and fertilization. A rising water table, salt accumulation, and other environmental problems appeared. As a result of these changes and the governmental poli- cies that helped to produce them. and population increase. Egypt ceased being a net exporter of food and began to depend on imports to feed its people. An example on the continental scale may be found in the British seizure of Australia. When they established penal colonies in the eighteenth century, they brought not only prisoners but also domestic animals and plants. along with exotic organisms such as rats and other mammals (later including, disastrously. rabbits). foreign trees. weeds, and dis- eases. all new to the ecosystems and formerly unknown to the aboriginal inhabitants. Within a few decades. the indigenous population fell to a fraction of its former number, and the landscape was transformed by deforestation. overgrazing, and soil compaction. The changes are not ï¬nished; when I was in Kakadu in the Northern Territory, a tribal elder told me of the damage done by water buffaloes in the wetlands, and the fear that large cane toads. introduced into Queensland to control insects. but which have devoured native wildlife there. may spread into his homeland. The ecological changes in Australia were as great as the societal alterations. and intensiï¬ed them. To give an example on the global scale, the explosion caused by human error and negli- gence at the Chernobyl nuclear power station in the Soviet Union in 1986 produced heavy fallout over hundreds of square kilometers and made an area of land uninhabitable. Radiation may be invisible, but its effects are often clear to see. Trees have died. plants have been observed to grow in strange sizes and shapes. animals have been born with mutations. and abandoned houses stand with children's toys still on the window sills. Those whom circumstances forced to stay in contaminated areas suffered radiation- induced illnesses. Radioactive particles fell over much of Europe. making crops and milk too dangerous to use for a time. and lesser increases in radiation were detected through- out the Northern Hemisphere. The event and its aftermath caused concern around the world and contributed to a sharp drop in the number of new nuclear facilities approved in many nations in the years afterwards.
4 History and ecology
These are examples of humans producing environmental changes that had major effects. intended or unintended. There have also been many cases in which natural causes have seriously affected human history. These include climatic changes. such as the Little Ice Age that forced the Norse abandonment of Greenland in the fifteenth century: volcanic eruptions like the explosion of Krakatoa in 1883 that destroyed the island. killed more than 36.000 people. and produced worldwide changes in the atmosphere: earthquakes as severe as the one (with an attendant tsunami or tidal wave) in 1755 that reduced Lisbon to ruins; cycles of population in various species, as for example the periodic outbreaks of locusts that have destroyed the crops in East Africa and other continental areas; and out- breaks of epidemics. of which the most famous is the Black Death that killed at least a quarter of Europe's population between 1347 and 1351 and altered the economic and political structure of late medieval times. The study of past events in which people have altered the environment. and in which environmental inï¬uences have changed human society. is the aspect of environmental history which is the subject of this book.
The task of environmental history is the study of human relationships through time with the natural communities of which they are part. in order to explain the processes of change that affect that relationship. As a method. environmental history is the use of ecological analysis as a means of understanding human history. It studies the mutual effects that other species. natural forces. and cycles have on humans. and the actions of humans that affect the web of connections with non-human organisms and entities. Environmental historians recognize the ways in which the living and non-living systems of the Earth have influenced the course of human affairs. They also evaluate the impacts of changes caused by human agency in the natural environment. These processes occur at the same time and are mutually conditional. William Green. in I-Ii.rtor_v, Historians, and the Dynamics of (3lmngcâ.'2 observed that no approach to history is more perceptive of human interconnections in the world commun- ity. or of the interdependence of humans and other living beings on the planet. than environmental history, which supplements and often challenges traditional economic. social. and political forms of historical analysis. An environmental historical narrative should be an account of changes in human soci- eties as they relate to changes in the natural environment. In this way. its approach is close to those of the other social sciences. One good example of this would be Alfred Crosby's The Columbian I:'xchangc.'3 which showed how the European conquest of the Americas was more than a military. political. and religious process. since it involved invasion by a European âportmanteau biota" including domestic species and opportunistic animals. Eurasian plants. whether cultivated ones or weeds. he noted. replaced native species. and the impact of introduced microorganisms on the indigenous human population was even more devastating than warfare. Like history itself. environmental history is also a humanistic inquiry. Environmental historians are interested in what people think about nature. and how they have expressed those ideas in folk religions. popular culture. literature and art. That is, at least in one of its aspects, environmental history can be a history of culture and ideas. It asks how atti- tudes affect human actions in regard to natural phenomena, and in search of an answer. describes what the signiï¬cant views were on the part of individuals and societies. Environmental history derived in part from a recognition of the implications of