1 Introduction
History and ecology
History is a saga of change. If people and the world around them remained the same from year to year and generation to generation, or merely repeated a cycle of growth and decay that offered no escape, there would be no history worth being writtenāor read. But fortunately or unfortunately, change is an inescapable phenomenon in human societies and the world of nature, and in the relations linking them. Challenges appear sometimes in the form of natural catastrophes that threaten the survival of communities, and at other times in the form of cultural and economic choices that threaten the ability of natural systems to endure and to provide necessary support for those communities. The past offers many instances of antagonism between humankind and nature, and other cases of restoration and hope. Ecological process has helped to shape the course of human history. 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 decline or even to disappear. This has happened in every historical period and in every part of the inhabited Earth. Dealing with the threats of the present and making informed choices for the future both depend on understanding the environmental experiences of the past.
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 highest peak reaches 1,861 m (6,106 ft), and on the northern coast, swells from the open ocean often produce thundering surf. Madeira was uninhabited until 1425, when JoĆ£o GonƧalves 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 islandās 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 also 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 isolated 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 cane5 at first and then grapevines that yielded the famous Madeira wine.6 A folk story says that the forests burned continually for seven years. An unknown number of native species perished from the fires and forest removal. Many non-native species were introduced, some intentionally and others 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, they 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 that escaped from gardens, forms thickets that choke out other plants, and in a similar invasion has virtually taken over the Azores Islands in recent years.9 On Madeiraās neighboring islet, Deserta Grande, a campaign in 1996 eradicated rabbits, and probably mice and goats as well, and both vegetation and native birds are making a remarkable recovery.10 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.11 But the native ecosystem of Madeira itself has been irreparably disrupted.
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 fifteenth century. Then Portuguese settlers arrived, constructed terraces, and planted vineyards whose grapes were used to produce the well-known Madeira wines. Photograph taken in 1999.
As an example offered at the beginning of this ecological history of the world, Madeira presents a question of scale. Madeira is a small island, only 57 km (35 mi) long and 22 km (14 mi) wide. The changes that take place there are local in scale, although they reflect 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 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 flood that watered and renewed the soil, depositing a layer of rich sediment. Then in the mid-twentieth century, a high dam constructed at Aswan ended the flooding. The structure itself, which I have seen from the river and from the air, is intimidating, vaster than the pyramids, but its effects on the land and people were even more enormous. Nubians who lived in the area of the new reservoir had to move elsewhere, and Egyptian farmers modified 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 policies 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 diseases, 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,12 overgrazing, and soil compaction. The changes are not finished; 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 intensified them.
To give an example on the global scale, the explosion caused by human error and negligence at the Chernobyl nuclear power station in the Soviet Union in 1986 produced heavy fallout over hundreds of square kilometers and made a portion of it uninhabitable. Radiation may be invisible, but its effects are often visible. 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 childrenās 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 throughout 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 following.
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 outbreaks of epidemics, of which the most famous is the Black Death that killed at least a quarter of Europeās 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 influences have changed human society, is the aspect of environmental history that is the subject of this book.
Environmental history
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.13 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 History, Historians, and the Dynamics of Change,14 observed that no approach to history is more perceptive of human interconnections in the world community, 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 societies as they relate to changes in the natural environment. In this way, its approach is close to those of the other social sciences.15 One good example of this would be Alfred Crosbyās The Columbian Exchange,16 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 āportmanteau biotaā 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 attitudes affect human actions in regard to natural phenomena, and in search of an answer, describes what the significant views were on the part of individuals and societies.
Environmental history is derived in part from a recognition of the implications of ecological science for the understanding of the history of the human species. This was appropriate, because ecology, in the sense that it studies sequential changes in natural communities, is a historical science. Paul Sears called ecology a āsubversiveā science,17 and when taken seriously by historians, it has certainly subverted the accepted view of world history as it was up to the mid-twentieth century. The older history made little contact with nature; it was concerned mainly with the political activities of human beings. When it dealt with nature at all, it portrayed the advance of culture and technology as releasing humans from dependence on the natural world and providing them with the means to manage it. It positively celebrated human mastery over other forms of life and the natural environment, and expected technological improvement and economic growth to continue to accelerate. Environmental history, however, recognizes the biological fact that humans are dependent on natural factors and subject to ecological principles. For example, it is an ecological principle that the ability of any organism to increase in number and total biomass, and spread geographically, will eventually encounter one of several environmental factors that prevent further increase. Growth is limited by the least available factor, and no resource is infinite. An ecologist viewing any other species increasing at the present human rate, and using a comparable proportion of the energy in an ecosystem, would predict imminent collapse. Also, ecology points out the value of biological diversity, which helps to maintain the balance and productivity of an ecosystem in reaction to moderate stress. The older history saw human replacement of natural diversity with monoculture, in terms of agriculture and civilization, as desirable. Environmental history looks at the land, with its human and non-human inhabitants, as a varied and changing mosaic in space and time.
Most importantly, a significant group of ecologists took the natural community as the subject of their science. The older history saw no important relationships beyond those within human society, but environmental history emphasizes in its narratives the importance of the interrelationships of the human species to other species and the conditions that make life possible. The older history, when it recognized that nature and the environment were present, treated them as a backdrop, but environmental history treats them as active forces.18
The community of life
This book endeavors to give an account of environmental history that portrays major ecological processes that were at work in each period from human origins to the present. The narrative is not an attempt to give a neutral...
