Saving the Earth

Article: People and the Land - Human Impacts on the Land

Before the advent of agriculture some eleven thousand years ago, all humans lived by hunting animals and sea creatures and gathering wild grains, nuts, fruits and vegetables. Early hunters utilized natural landscape elements to aid in hunting, particularly herd animals which could be directed into natural traps so they could more easily be killed. These skilled hunters quickly hunted the megafauna of North and South America, Asia and Australia into extinction within a few generations of moving into these continents. Native Americans and other indigenous peoples used fires to keep the understory of forests clear of brush to aid in hunting.

With the development of agriculture it became possible to provide a reliable food supply for larger numbers of people. Populations grew and, over time, became more settled in locations that provided optimal conditions for growing crops and tending domesticated animals.

Agricultural practices have, from the very beginning, reshaped the land: forests were cleared for cropland; terraces built to halt erosion; irrigation ditches were dug to provide ample water for crops. Watercourses were dammed or diverted to aid in irrigation. Erosion of cleared land moved soils around.

Eventually these routes were improved by grading, drainage, surfacing, clearing of obstacles and building causeways or bridges to cross marshy land or streams and rivers.

With the development of cities in the Fertile Crescent of the Middle East some five thousand years ago, these urban settlements caused increasing changes in the land. Within cities were permanent structures, built of mud, brick, wood or stone – materials that were gathered and transported to the building site. Forests were cleared for wood and fuel, quarries yielded stone and other materials.

Larger groups of people required a reliable water supply for drinking, cooking and sanitation. Wells were dug, reservoirs constructed, rivers dammed and canals and irrigation ditches were constructed. Farmland, orchards and pasturage lands increased to feed the growing population.

As human populations increased, the environment was altered in many different ways. Wars, famines, floods and other natural disasters affected the course of settlement, depopulating areas, moving populations, destroying cities which were either rebuilt on the old ruins or abandoned for new locations. Population growth increased the pressure on wildlife which was hunted for food, hides and other natural materials. Animal populations decreased from over-hunting and fishing, and from habitat degradation, such as deforestation and siltation of streams from the erosion of agricultural lands.

As humans lived more closely together and in close proximity to livestock and domesticated animals, the spread of disease was facilitated by poor sanitation, malnutrition, and animal-to-human transmission. Many human diseases were originally resident in animals before mutating into forms that could infect humans. When these mutations first occurred, human mortality was usually quite high until enough people developed antibodies that could mitigate the impact of the pathogens.

Many features of the landscape that appear to be “natural” are the result of human activity. Researchers believe the Great Plains were created in part by fires set to create more wide-open habitat for the herds of bison which formed the basis of Native American  subsistence and material culture. Hills, valleys, clearings, watercourses – all may appear to be a natural part of the topography but upon inspection yield evidence of human settlements, buildings or shrines, former agricultural land, industrial activities, or canals and irrigation ditches.

Since the Industrial Revolution first darkened the skies over Europe in the late eighteenth century, human impacts upon the Earth have intensified as coal and iron ore have been extracted in huge quantities; forests cleared for wood and charcoal; and the land, rivers, oceans and atmosphere have been polluted by industrial byproducts and waste materials.

Industrial manufacturing created a voracious appetite for raw materials. Billions of acres of cropland were devoted to monoculture farming of cotton, wheat, corn, and rubber trees; millions of whales were killed so their blubber could be rendered into whale oil, which lubricated the pistons and gears of the Industrial Revolution. Billions of tons of coal, iron, copper, tin, bauxite and other raw materials were mined. Huge quarries labored to produce limestone, granite, marble and other building materials.

Though coal is still heavily used to power electric generating facilities, most of the energy used worldwide since the late nineteenth century comes from petroleum and natural gas. Presently, some 85 million barrels of petroleum are extracted from the ground each day, as well as 9 billion cubic meters of natural gas.

Pumping groundwater for agricultural irrigation is depleting deep underground aquifers of water deposited there thousands of years ago (“fossil water”). Overuse of irrigation is causing salinization of soils; runoff of chemical fertilizers is killing fish in streams and creating enormous dead zones in the ocean outside river mouths, where no ocean life can live.

The ocean itself is being plundered by industrial fishing methods, which drag enormous trawls across the ocean floor, scraping it clean of all undersea life and indiscriminately taking all fish in its path. Many species of fish are no longer commercially viable; cod, which were once the most numerous fish in the Atlantic, are virtually extinct. Most runs of salmon worldwide are now extinct.

The exponential growth of human populations and industrial output worldwide has created an unprecedented level of human impact upon the Earth. We are now pumping 27 billion metric tons of  CO2 - the major greenhouse gas - into the atmosphere per year; these gases refract the sun’s rays, raising the temperature of the Earth’s surface. This global warming is literally changing the climate: the polar icecaps are melting at an accelerated rate, and sea levels are rising worldwide. Many Pacific islands and major population centers worldwide will be under water with a rise in sea level of only a few feet.

The books recommended in this section on People and the Land show, in words and pictures, the impact of people upon the landscape. The field of ecological history details changes in the landscape from hunting, agriculture and industry while historical overviews relate environmental degradation to the collapse of major societies (Anasazi in the American Southwest, the Vikings in Greenland, modern Rwanda). Stunning satellite photography brings home to the reader the enormity of the changes we have wrought. Ecopsychological works examine the effects upon people of ecological impoverishment.

David Yarian, Ph.D.

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