ENVIRONMENTAL IMPACT, HUMAN

Since the late nineteenth century, changes to the global environment have been profound–and mostly in the direction of degradation. Such changes include ozone destruction, widespread smog, devastating erosion, river blockages and channelization altering water flow and preventing nutrients from reaching deltas and seas, the frenzied clearing of tropical forest for timber and arable land, the collapse of ocean fisheries and other common-access resources, and heightened extinction rates. As the historian John McNeill chronicles, humans, propelled by population growth, migration, and urbanization, and by the worldwide drive for development with its penchant for the industrial "Motown cluster" of automobiles, oil, chemicals, and plastics, have powerfully transformed the planet.

But as the cultural geographer David Lowenthal once astutely pointed out, "the acceleration of environmental transformations blinds us to their antiquity." Antiquity is the focus here: Did human hands aggressively shape the environment prior to the modern or industrial era? Did indigenous people walk lightly on the land? People in preindustrial times surely possessed comprehensive environmental knowledge and were ecologists in the sense of thinking about the environment and its components in interrelating, systemic (but always culturally specific) fashion; some were environmentalists in their expressed concern for the state of the environment. But what counts when considering the human impact on the environment is how people behaved. Did they conserve resources–that is, intentionally use them wisely to maintain their future availability, and avoid waste, despoliation, and the like–or did they take quite different action with other ends in mind, leading rapidly or ultimately to depleted resources and unsustainable futures?

Despite widespread infatuation with the late-twentieth-century image of indigenous people living lives consistently in balance and harmony with nature, the answers to these questions are complex. They can be sought in the scientific, archaeological, and historical record, as well as in ethnographies of nineteenth-to twentieth-century indigenous people living traditional lives. The latter offer useful ways to imagine preindustrial times with respect to the use of fire, animal extinctions, food production and village life, and extirpations linked to the emergence of market economies. Special attention is given here to the North American case.

Fire

Human-induced fire is as old as our species, Homo sapiens, and might have evolved as long as one-half to one million years ago as one of the earliest hominid tools. The evidence of fire is in the archaeological and historical record on all continents and innumerable islands. Because fire has transformative effects on ecosystems, landscape–that is, culturally modified environment–is as ancient as humankind. Wilderness, defined as territory untrammeled by humankind, became increasingly uncommon after humans began using fire.

North America, for example, was far from the pristine, primeval land the Europeans imagined it to be when they arrived. Instead the continent, as noted by an early-seventeenth-century Dutch mariner off the East Coast, was "smelt before it is seen." Everywhere, the Native American Indians torched the land. They burned to improve subsistence, to create favorable ecological niches, to drive animals from one place to another, to increase production of crops or berries and other gathered foods, to set the stage for new plant growth that would attract herbivores and, in turn, carnivores in another season. They knew what would happen to the land and to plants and animals as a result of their burns. Their use of fire revealed keen awareness of the systemic interrelationships that are at the core of the conception of an ecosystem. Indians possessed their own theories of animal behavior (ethnoethology) and gave ecosystems cultural definition with spaces and links that would not necessarily appear in a Western conservation biologist's depiction of the ecosystem. They were ecologists, if ecology also can be ethnoecology. But these first North Americans did not always burn with ecological consequences in mind. Some often used fire as an offensive or defensive weapon, to drive enemies before them or to cover their own escape. Many lit fires to send signals to each other, communicating a variety of desires and plans. Others who lived in forests set them ablaze to ease travel. Many of these fires, as well as others, raged beyond control, deeply scorching the land beyond short-term utility, killing animals, and burning until extinguished by rain or halted by rivers.

Determining the precise ecological consequences of long-past fires can be daunting because archaeologists cannot always know whether fires were natural (caused by lightning) or anthropogenic. Yet in North America certain ecosystems are fire-succession ecosystems in which human hands were present in their maintenance if not at their inception. For example, widespread ponderosa pine forest requires periodic fire to eliminate competing understory, and in the absence of fire these pines grow so densely that the forest stagnates or changes to one dominated by shade-tolerant species. Chaparral, a scrub community in the North American West, is fire-induced and will endure as a robust ecological community only if managed by fire (which many Indians did, to the benefit of useful plants and the animals attracted to them). Longleaf pine forests in the Southeast require regular fires to remove competing plants and destructive fungus. Longleaf pines are fire-adapted in growth and in fire's absence fail to reproduce or survive, and the forest changes to one dominated by other pines and deciduous trees. Finally, the eastern sections of the vast North American plains and prairies, where moisture allowed natural succession by oaks, aspens, and willows, were maintained and quite possibly induced by human-originated fires.

In short, when Europeans gazed upon North America for the first time and many imagined an untouched Edenic wilderness, they actually were looking in large part upon a cultural, anthropogenic landscape produced and maintained by fire. Many landscapes in other regions of the world had similar pyrogenic histories.

Animal Extinctions

Humans are implicated in animal extinctions long before the highly publicized ones of the modern period. One episode occurred at the end of the era known as the Pleistocene in North America, where the destruction of numerous species of animals followed closely on the heels of the initial arrival of hunting-gathering Paleoindians some 13,000 to 14,000 years ago (Australia has a similar history at an earlier time). The Pleistocene extinctions were remarkable. At least 35 mammalian genera disappeared, many in the millennium beginning 11,000 years ago. Animals familiar and unfamiliar, widespread and local, and large and small vanished. Many were large animals, the so-called megafauna: hulking, tusked mammoths and mastodons; slow-moving giant ground sloths; the armored 2,000-pound, six-foot long glyptodonts, a kind of giant armadillo; single-hump camels; 300-pound giant beavers; hyena-like dire wolves; short-faced bears; scimitar-toothed and great saber-toothed cats, and others.

Debate is sharp over why these animals became extinct. Some researchers point to climate, which can be linked to six other extinction episodes in the last ten million years in North America. The climate was in the throes of significant change at the end of the Pleistocene, when temperatures warmed markedly, and winters became colder and summers hotter. Entire habitats changed overnight. Grasses, plants, and invertebrate and vertebrate organisms flourished or died. Were the consequences dire for key herbivores with the potential to transform the environment, and therefore for species linked to them? There are more questions than answers about the consequences of climatic and vegetational changes on specific species, and about the precise mechanisms involved in the impact of climate on particular species.

Moreover, unlike earlier extinctions in North America, during the Pleistocene extinctions there existed men and women with a distinctive hunting technology and definite taste for species now extinct. Humans' likely role in the extinctions is argued by the other protagonists in the debate. Perhaps climate change left certain animals susceptible to a Paleoindian coup de grace.

One way to think about what happened in North America is to consider the large island of Madagascar, where, in the wake of human arrival some 1,500 years ago, large flightless birds, giant tortoises, hippos, more than 15 species of lemurs, and other animals became extinct. They vanished after people appeared during a long dry spell in an oscillating (wet to dry) climate. This coincidence doomed more species than either humans, desiccation, or vegetation changes alone could have.

Yet even in the absence of such coincidence, preindustrial humans were highly efficient predators who, under the right conditions, were fully capable of depleting faunal resources. For example, as people colonized the Pacific (1600 b.c.e. to 1000 c.e.), they induced widespread environmental change and exterminated thousands of species of birds. In Hawaii, colonizers cleared land with fire, diverted streams for irrigation, transformed forested coastal areas into farms and grasslands, changed mudflats into fishponds, and introduced animals. Birds vanished with their habitats or were overwhelmed by their utility as food or commodities (for example, feathers to ornament clothing); over one-half of endemic avian species were extinct when Europeans arrived. This pattern was repeated on other islands. Birds and some other animals almost completely disappeared from small islands like Easter Island, Mangaia, and Tikopia. Even on the large island of New Zealand, Polynesian colonizers deforested vast sections of the land and hunted 13 species of moas–ostrich-like flightless birds, one of which towered over men and women–to extinction before turning their attention to the small birds, shellfish, fish, and seals that remained.

Food Production, Population Size and Density, and Village Life

The extinction of birds in the Pacific is just one example of environmental change caused by food producers. From 8500 to 2500 b.c.e., a potent combination of forces for change emerged independently in Southwest Asia, China, Mesoamerica, the Andes, and what is now the eastern United States: permanent villages occupied by more people living more densely than before, with economies based on domesticated plants and animals. This way of life, anchored in food production, spread to other parts of the globe. It supported population densities 10 to 100 times as great as in most foraging societies (even as such crowding left people susceptible to diseases originating in domesticated animals and unsanitary conditions). Demography was not the only important determinant in this changing relationship between humans and the land–acquisitive intentions, resource abundance, impact of technology, and precise environmental understandings played important roles–but it was nevertheless significant. Everywhere it was practiced, this new way of life contained potential for significant environmental change–in villages and especially in the most densely settled areas where urbanism emerged.

In America north of the Rio Grande, where there were probably no more than 4 to 7 million people on the eve of European arrival (equal to the 2000 population of Colorado or Virginia), the pressures could be sensed in the Southwest and along the Mississippi, where densely-settled societies emerged, flourished, and (from the eleventh through fourteenth centuries c.e.) disappeared. These changes happened because the settlers' demand for wood for fuel, construction, and other purposes overtaxed forests; because they did not foresee the long-term consequences of delivering, through irrigation canals, saline waters to salt-sensitive crops planted in salty fields where the water table was high; or for other reasons. Farther south and centuries earlier, the Maya had degraded and deforested their own terrain, which with other factors set the stage for the abandonment of their striking ceremonial centers by 900 c.e..

These events repeat the pattern established earlier in the Old World. Canal siltation, waterlogging, and salinization doomed urban life in Mesopotamia, despite the shift from wheat to salt-resistant barley. People in the Near East denuded forests to satisfy the demand for wood, especially for use as household fuel and to prepare lime plaster. Domesticated animals (not an environmental problem in the Americas) were an important part of the production mix and were clearly linked, through heavy grazing, to defoliation and erosion. In ancient Greece and Rome, deforestation and erosion, which were prominent environmental problems, were caused by clearing lands for cultivation; grazing by cattle, sheep, goats, and pigs; and the demand for charcoal for domestic fuel and lumber for building construction and shipbuilding. Deforestation was extensive in many parts of the classical Mediterranean world. Permanently eroded and degraded, these lands were subject to flooding, siltation, desiccation, and disease–all clearly worrisome to some contemporaries who remarked upon man's effects on nature. As the archaeologist Charles Redman suggests, productive strategies often seem to have undermined whatever balance might fortuitously or deliberately have existed in cycles of decline and recovery, and to have left societies vulnerable to the unexpected–like adverse climate change.

On the eve of the transformations leading to the modern era, fifteenth-, sixteenth-, and seventeenth-century Europeans profoundly altered entire portions of their continent. Woodcutters in search of fuel, iron and other mineral smelters on the make for charcoal, and farmers seeking new arable land all assaulted forests on a broad front. Naval and merchant interests could never get enough timber for ships. Hunters systematically killed wolves and other predators. In England, marshes were drained for conversion to arable land. People engaged in brewing, brick making, dyeing, and other industries oblivious to the environmental consequences. Urban skies were darkened by the pollution from burning sulfur-laden coal. Some fled to the countryside as an escape from modern ills, but many went about their lives seemingly without regard for the wastes that fouled water and air.

Commodity-Linked Extirpations

From ancient times, as production rose above subsistence levels, the development of trade and markets increased the pace of environmental exploitation. In ancient Greece and Rome, for example, the demand for wildlife products in household and military subsistence, the commercial marketplace, private sport, and the arena led to the widespread decline of animal stocks and extirpations both on islands and the mainland. The need to protect domesticated crops from competing grazers and domesticated animals from predators also contributed to extirpations.

Environmental destruction reached a new level with the rise of capitalism in seventeenth-century Western Europe. The subsequent global spread of Europeans affected the environmental history of all continents. In North America, Europeans arrived along with microbes that were harmless to them, inadvertently unleashing horrific epidemic diseases among the Indians. These diseases killed great numbers of indigenous people and in the short run lessened pressures on ecosystems. But the Europeans also came with an unrelenting and expansive belief that environmental goods were commodities for exploitation. This commodification of the environment, together with increasingly capital-intensive industrial designs, ultimately proved profoundly transformative. Indigenous people responded by becoming primary suppliers of environmental goods such as animal pelts and skins in exchange for a variety of desired, highly valued consumer goods. The two most famous commodities from the sixteenth through the nineteenth centuries were deerskins and beaver pelts, willingly supplied by indigenous people to the point of extirpation of white-tailed deer and beaver populations.

It is often assumed that indigenous people like the Native Americans possessed a primordial conservation ethic that they abandoned as they participated in Western systems of commodification. If the global ethnography of hunting and foraging people in modern times is any guide, this assumption is erroneous. Restraint in harvesting wildlife is rare among such people, who instead make choices that maximize efficiency or promise high yields. Moreover, in the case of the North American Indians, the hunt was ruled by culturally defined respect for prey species which, properly approached in thought and deed, gave themselves up for sustenance and use and thereby gained the opportunity to be reborn to be killed another day. For restraint to be practiced, this indigenous belief in reincarnation had to be reconciled with Western-style conservation.

Conclusion

Neither the antiquity of environmental change nor the enormous scale of transformation in the modern global environment should be in dispute. In some cases, ancient and modern behavior produces similar results: Extinction of a species is forever, whether at the end of the Pleistocene, on a Polynesian island 500 years ago, or in twentieth-century North America. Moreover, some small-scale modern environmental changes at least superficially mimic ancient ones associated with the emergence of densely settled village life based on domestication. The major difference is one of scale, linked to population size and technology: In the past, the changes were local or regional; in the early twenty-first century they have global potential. The tempo of change has also risen markedly. Yet one should be humbled by the fact that the consequences of ancient destructive practices are often visible today–although noting the irony that, in places like Greece, the long history of environmental degradation produced the aestheticized landscapes that many now admire, in ignorance of their origin.

See also: Biogeography; Carrying Capacity; Ecological Perspectives on Population; Hunter-Gatherers; Prehistoric Populations; Sustainable Development.

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Shepard Krech III