A Paradigm of Human Use of the Earth

A Paradigm of Human Use of the Earth


It is said hunters and gatherers lived lightly on the land, though some lived more lightly than others. North American Indians eliminated some sea mammals along the California coast and ate the biggest oysters in Chesapeake Bay. Earlier on, Native Americans in the late Pleistocene, only 50 or 60 human generations removed from us (they were then new immigrants from Asia), helped exterminate the so-called Pleistocene megafauna, the large mammals (mammoths, mastodons, camels, horses, sloths) in North and South America. Their hunting probably forced the evolutionary development of the plains bison into a smaller and earlier maturing beast. Burning, to renew the berries and browse of a woodland for game, to drive game animals, to keep grasslands open, changed whole landscapes. It moved the prairies east, opened meadowlands in the eastern forests, and created open forests of fire resistant trees (many large and old) such as the mountain forests of the western United States, the park-like oakwoods of southern New England, and the southern forests of longleaf pine. Burning by Australian aborigines transformed the landscape of Australia, turning shrubland into grass, and was probably one reason so many Australian animals went extinct shortly after the aborigines arrived. Hunting and gathering was an adaptation that worked. Human populations slowly grew.

The development of agriculture was probably related to increasing human population and a drying post-glacial climate, and the related failure of some gathered foods. With agriculture, human influence on the earth increased. An ideal natural world became a cultivated one: a garden. Forests were cut or grasslands cleared to grow grain, rivers were diverted for irrigation, hillsides terraced to grow maize and rice. Forests were also cut for cooking fuel, to burn brick, smelt metal ores, build houses and ships. Grazing animals, whose meat, wool and skins helped feed and cloth the people in the villages, kept the trees from regrowing. Greek shepherds girdled trees to increase the grass. Eroding soil raised river beds, silted harbors, pushed river deltas far out to sea. By 8000 years ago the removal of forests and the cultivation of the ground, by increasing the release of carbon dioxide from forests and soil, was raising the level of carbon dioxide in the atmosphere. The development of paddy rice cultivation 5000 years ago increased the level of methane in the atmosphere (methane is another greenhouse gas that oxidizes to carbon dioxide). Together these gases warmed the atmosphere sufficiently to prevent the start of another continental glaciation, whose glaciers had begun forming 4000-5000 years ago in northeastern Labrador. The ice melted under the benign climatic conditions produced by early agriculture. So our unheard of 10,000 years of favorable climate is partly a human artifact.

Early agriculture was hard on the land (though Romans understood the benefits of crop rotation) and farmland wore out as nutrients were used up and topsoil eroded. Upland fields were being abandoned in Jordan 8000 years ago. About the Mediterranean, during the Bronze Age (and in many cases continuing until modern times), less favorable lands (hilly uplands) were farmed and abandoned in 1000 year cycles. The new settlers would come upon the foundations and walls of their predecessors amidst the dense scrub. Once forested high uplands, warm and moist enough for trees, such as the Andean altiplano or the Tibetan plateau, became grazing lands, with scattered cultivation. Some lands, such as the Negev Desert of Israel (indeed, much of the Middle East and North Africa), were essentially denuded, their hills eroded to gravel, during long periods of occupation. Irrigated lands, such as those in the Tigris and Euphrates Valley of what is now Iraq, salted up over a thousand of years of irrigation, and were also abandoned. Deserts were created, partly by the drying of the climate, partly by the removal of their vegetation. This process has continued until the present. Degraded and abandoned land worldwide now amounts to about 5 billion acres (enough for 0.5-1 trillion trees).

Until the development of fossil fuels, the human habitat was more or less limited to the natural world, though agriculture manipulates the natural world considerably more than hunting and gathering and so supports more people per unit of land. In an agricultural society, increase in the food supply depends on developments in agriculture, or new land. The human population was capable of much faster growth—exponential growth, as Malthus pointed out—and even if populations were limited (by late marriage, taboos on intercourse, or exposure of infants, all only partly successful) poverty and hunger in agricultural societies were common. Long cycles of relative prosperity and depression, along with cycles in the settlement and abandonment of marginal lands, dominated European history for the last few millennia, and probably also the histories of other settled agricultural regions. The material life of a peasant in 16th century Europe was little different from that of one in Roman times. The collapse of agricultural societies from soil erosion, soil saltation, or slight changes in climate (Sumeria, Egypt’s Old Kingdom, the Maya, the Anasazi of the North American Southwest, the pre-Inca Tiahuanaco civilization, Rome) was common.

The invention of the coal-burning steam engine changed all this. The engine was used to pump water from the mines, in order to mine more coal (or iron ore). The coal powered the trains that transported the coal, the trains manufactured of (and running on tracks made from) coal-smelted iron. Coal and iron ore were essentially inexhaustible. Cheap transportation by steam ship meant food could be quickly transported all over the world. Coal became the basis of the modern chemical industry, replacing or supplementing wood (once distilled into several components), oil seeds and fiber plants and animals as a natural resource. The invention of a method of manufacturing nitrogen fertilizer from nitrogen gas in the air, the energy for the reaction supplied by coal, doubled or tripled crop yields and meant the nitrogen-fixing legumes formerly used in rotation to renew soils could be disposed of and food crops grown in their place, increasing the area of cropland by 30-50%. Coal heated houses, baked bread, brewed beer, ran factories, lighted houses. In newly settled lands wood, if abundant, might replace coal for a time. During the twentieth century other fossil fuels (oil, natural gas), along with hydroelectricity and nuclear power, helped supply the increasing energy demands of modern society. Capital, formerly limited to returns on agricultural investment or real estate (both limited by population growth, of people, crops or animals: capital comes from the French word for cattle), where returns might be 3-4% a year, found enormous returns in the developing markets of a rapidly growing world. As Fernand Braudel remarked, the ceiling on human possibilities vanished. For the first time since the development of agriculture, there was plenty of food (if you could afford it); and a limitless supply of energy. Population doubled every 25 years in newly settled North America, rather than every few hundred years in Europe, and the landscape was settled at half a percent (later 1%) a year, leading to enormous returns on investments in land. More capital meant more investment and more manipulation of the landscape.

Between 1850 and 1980 five billion acres of new land were cleared, in North and South America, Australia, and Eurasia. Forests were turned into fields, their timber burned or sawn, and the ashes sold; grasslands were plowed. Rivers filled with silt eroded off the fields and with sawdust from the mills, their fish spawning sites buried; and later with industrial effluent, petroleum and sewage. Steam driven trawlers scraped the bottoms of the oceans bare, breaking off their coldwater corals and sessile plants and animals, habitat for juvenile cod, hake and halibut. Scallop trawls brought up the bottom itself, which had to be shoveled, minus the scallops, off the deck. Sulfur dioxide, various hydrocarbons, soot and heavy metals from burning coal, from coke plants, from metal smelters and foundries filled the air, and men’s lungs, and settled out on the land and washed into waterways, where they ended up in the organs and flesh of fish. Modern suburbs were, like ancient ones, an escape from polluted and dangerous cities. After World War II and the development of the modern chemical industry, based largely on petroleum and chlorine, these materials were joined by tens of thousands of more or less toxic and bioaccumulating chlorinated hydrocarbons. At the same time, human prosperity and population reached unprecedented levels. All this, together with human settlement patterns (dispersed by the car), and—with the growing amount of machinery and capital—the increasing human ability to “pick up” the environment (eliminate, say, the tiny pools where amphibians bred, and which migrating shorebirds visited, and turn everything to pavement, plowed fields, planted forests, lawns), affected animal and plant populations, many of which began to disappear. Some, like songbirds and large game animals, seemed to stabilize at 5-10% of their former abundance in the late twentieth century. In 1958, a scientist named Charles Keeling set up instruments on a mountain in Hawaii to measure the carbon dioxide content of the atmosphere, to answer a simple question: what’s happening with all that carbon dioxide? The curve of carbon dioxide went steadily and increasingly up. In the 1970s, the possibility of global warming, from carbon dioxide and other gases produced by the burning of fossil fuels, from land clearing and agriculture, among other activities, was a crazy idea, by the 1990s not so nuts. Human contribution of carbon dioxide to the atmosphere was reaching 10% of that fixed annually by photosynthesis; while human contributions of usable nitrogen to the biosphere (nitrogen usable by plants: from fertilizer, planted legumes, animal manure, combustion of gas, coal, oil) equaled the natural contribution. Human intervention in the biogeochemical cycle of sulfur was reaching 30%. Paleoclimatological correlations of carbon dioxide and temperature in the past made the modern situation ominous. Temperature changes were obvious in the modern Arctic, where the sea ice was melting and the permafrost collapsing. And in the temperate world the movement of birds, mammals, plants and butterflies north or upslope was well documented: the plants and animals knew something we didn’t.


When a plant or animal, freed of its native parasites and predators, expands into a new habitat, it often overextends itself. Meadow voles, released on a grassy island without predators, will increase until no vegetation is left; then the population crashes, the vegetation (somewhat) regrows, and a much smaller population of voles cycles around a much smaller food supply. Fossil fuels let us construct a new habitat on the whole planet. This process is still going on. The use of fossil fuels freed us from the constraints of organic agriculture and from the limits of energy that came from wind, water and growing trees. At the same time, antibiotics, public health measures and insecticides freed us from most debilitating diseases and parasites; inorganic fertilizers, machine power, irrigation dams, and advances in crop breeding let us expand the agricultural environment virtually indefinitely; trawlers dragging huge nets led to increasing amounts of wild fish, until cultivation of fish (together with fish breeding) began to replace wild catches. The human population rose from 1.6 billion in 1900 to 6-7 billion now, quadrupling (worldwide) in a century. In 2009 the amount of carbon dioxide in the air has already sealed the fate of mountain glaciers that support the flow of rivers that irrigate food for 2 billion people in Asia, as well as the Arctic ice pack with its polar bears, foxes and seals. It will reduce the spring flow of rivers in California, warm continental interiors that are already too warm for good pollination of grain crops in parts of the U.S. South, produce more widely spaced but more intense rains. In 2009 northern forests are collapsing from insect infestation brought on by warmer, shorter winters; the fisheries off industrial coasts are degraded from overfishing and too much anthropogenic nitrogen; chlorinated hydrocarbons, many of which are cancer-causing and/or mimic human hormones continue to accumulate in fish, seabirds and human fat; the sea is rising and becoming more acid.


What to do? Will we reduce our population to 1.5-2 billion people, and reduce our energy use, so those people (2-3 generations of women with one child would do the trick) could run their economy on wind, water, sun, some nuclear and geothermal power, and live within a working biosphere. If we don’t do reduce our population, nature will do it for us.

Some claim the economy a subset of the biosphere. It’s hard to make an effective economic argument for preserving the more charismatic biota of earth (redwoods and grizzly bears; maple trees and chipmunks). On the other hand, the earth’s microbes and invertebrates are essential, being involved (among other things) in decomposition of plant and animal material; the production (through photosynthesis) of oxygen and (through respiration) of carbon dioxide (without some carbon dioxide, the planet would turn into a snowball); the fixing of reactive nitrogen plants can use from inert nitrogen gas in the air; the formation of sulfur compounds (also necessary for plant life). The larger biota (trees, grasses) affect microclimate and (to a lesser extent) the climate over large areas (largely through affecting temperature and rainfall: thus forests extend inland from rainy western coasts). Forests and grasslands control runoff, filter out silt and regulate the chemistry of surface waters and thus influence the lives of fresh water fish (more charismatic biota) and the health (their chemistries, silt loads) of estuaries, the main nurseries for marine fish and invertebrates. In short, they help set favorable conditions for other charismatic biota, in a world formed by invertebrates and microorganisms. Off shore islands, stabilized by grasses and trees, and tidal wetlands (ditto), along with coral reefs, protect sea coasts from storm surges.

Agriculture, together with more minor activities like forestry and fishing, is the human activity that depends directly on a friendly biosphere: that is, on predictable cycles of temperature and precipitation, on predictable river flows, on abundant insect pollinators and abundant insect, avian and mammalian predators of crop pests (beetles and bats help considerably), on the life of the soil. Most of the modern economy depends on stored life: fossil fuels (and their combustion and conversion into chemicals); various probably lifeless minerals; and metal ores (some of which are the products of past life). How much of the biosphere do we need? Food could be produced under plastic greenhouses, cooled by seawater pumped from cool depths, watered by dew condensing from the pipes, on artificial soils; our diets supplemented by the products of various bacterial fermentations. Desert coasts (also energy rich) would become the new agricultural lands. There is no shortage of schemes to bypass the agricultural biosphere.

Of course such ideas are nuts. The fundamental mistake of economics is the assumption that what is made doesn’t matter. This simplifying assumption means the science of economics is quite disconnected from the real world. Such disconnects are what government must compensate for (with, for instance taxes on carbon emissions or bio-accumulating chemicals). Climate change, sea level rise, the increasing pollution of the environment by industrial chemicals, the collapse of the oceans and of populations of land plants and animals, may not be the worst things that will happen to people over the next century: wars over food, religion and water are also likely. But those wars will take place against the inevitable collapse of the environment that sustains us, and in which we have evolved.