The Natural History of the Present, Chapter 2

Chapter 2: The Land Trip
In general, the more that is invested in a landscape, the more it’s worth. Put another way, the more human manipulation a landscape undergoes, the greater its market value, and the less its value as an ecosystem. Capitalist manipulation of a new landscape begins with harvesting the natural wealth that has accumulated over time: furbearing animals, fish, mussels, timber, topsoil, or (over a very long term) minerals such as iron ore and coal. Such wealth can be extremely valuable. Beaver pelts—80,000 per year were exported from Dutch settlements in New York State in the 1650s—built many buildings in 1600’s Amsterdam. Virgin forests in the eastern United States hold 3 to 6 times the standing biomass of second-growth, and they yield 10 to 20 times the board footage of lumber. The aboriginal societies that inhabited the landscape used the forest differently—for harvesting acorns and hickory nuts and the animals that feed on them, for firewood, building material, medicines, basketry fibers, material for making canoes. Many large old trees remained. These peoples manipulated the landscape by hunting large herbivores, which affects plant succession, and by fire, which has a large effect on the landscape. Some of their uses were not sustainable. But virtually no current capitalist use is sustainable. (One can point to a few groups of farmers, and a few wild fisheries, such as the salmon fishery in Alaska and perhaps the lobster fishery in the Gulf of Maine—though its success depended on the fishing out of the cod; but in general in a capitalist world, resources are harvested as fast as the market will absorb them.)

Capitalist economics influences the biological as well as the man-made world. Resources like trees and soil become commodities rather than the defining elements of landscapes. Once economically useful soil-conserving landscapes are abandoned because they become too labor intensive to exploit, such as hillslope terraces in Greece or Peru, or tiny vinyards on slopes along the Rhine. Some economic landscapes are abandoned because further exploitation is no longer possible, such as the Roman mines that still pollute rivers in Spain. The products of human effort (fields, mines, factories, downtowns), having repaid the capital invested in them, erode, breakdown, decay. During the settlement of the United States, once a landscape’s natural wealth was gone (the furs, timber, game; the beaver that made an economic success of the colony at Plymouth; the live golden eagles one could buy in the game markets of American cities in the 1820s), a piece of land might be worth very little. The place however remained and it might also be worth a great deal as building lots or farmland. During the settlement of western New York State after the Revolution, it was said that unimproved forest land increased in value 2 to 3 times over 10 years, while land cleared and converted to farms increased 5 to 20 times. The firewood cut off an acre would pay for the clearing of another four acres; and the cleared land could be sold at a profit. One could buy a farm for a year’s labor. In Europe in 1790 a year’s agricultural labor would buy one’s family food, the right to collect firewood, and some sort of shelter. While most of the land east of the Mississippi was wooded, until the railroad made shipment of bulk commodities profitable, much of the timber removed in clearing land was not marketable as timber. It cost too much to ship: 50-75% of timber’s retail value consisted of transportation. Timber was more marketable as converted ashes or potash, whose value per unit volume was much higher than sawn lumber or firewood. Potash was an important nineteenth-century industrial chemical used in the manufacture of glass, soap, gunpowder, and in bleaching linen and scouring wool. About 5% of the several tons of hardwood ashes produced by burning an acre of old growth forest would convert to potash. The sale of potash would pay for the land and its clearing. Converted wood ashes were among the first goods shipped east on the Erie Canal.

A landscape’s annual return determines its value. In general, though not always, a landscape’s return is a measure of how much has been invested in it. The manipulation such investment implies is usually inversely related to the land’s natural value; that is, to its function in the biological world. For instance, land used for forestry is worth less than land used for agriculture. This is because agriculture yields a much higher annual gross return. Agriculture’s higher return depends on more yearly investment and manipulation, as the farmer puts labor and money into his land. Grazing land, which requires less human input than land used for row crops, is worth less than cropland, and yields less gross return. The biological effect on the landscape from grazing, where domestic animals do the work, is considerable, but in general pasture land, especially if not overgrazed, retains more of its natural functions than land in row crops. Logged forestland retains more than pasture. (There are limits here: most human uses fall along a continuum and the ecological effects of grazing and logging can be extreme.) Gross income per acre is a measure of the annual manipulation of the landscape, and thus indicates its integration into and importance for the larger economy. Manipulation and development usually create pressure for more development. Farmers for instance, need machinery, chemicals, fuel, transportation, housing, credit, insurance and services; and much more of all this per acre than loggers. More farmers require more of all this, and more people benefit. Local governments, banks, oil companies, farm equipment dealers, insurance companies, real estate agents all see a rise in their incomes and all push for more development: more farms, more subdivisions, more downtowns, more infrastructure to support all that.

If it works, land development is always profitable to the landowner, though it may not be profitable to the society as a whole. In the middle of the nineteenth century, unclaimed wetlands in in the Middle West (river overflow land, swamp forest, swampland, lands still owned by the federal government) was granted to the states, who were supposed to sell it to raise money for drainage, in order to turn it into farmland. Drainage is expensive. Land speculators bought much of the land, began drainage schemes, then tried to resell it. Private drainage schemes along the Mississippi and its tributaries usually failed. Many were taken over by the government. Some were completed and the investors never paid (agriculture couldn’t pay the costs). Drainage eliminated the public goods such lands performed, such as flood water storage, which reduced the height of floods along the river, and the removal of silt and nutrients from river water. Overflow lands provided spawning areas for fish and greatly increased the productivity of the riverine fishery. The silt and nutrients the floods spread on the swamplands grew trees, game, and fish rather than overfertilising the river. All these services were free as long as the land was left undeveloped. After development, such functions were replaced with more economically valued goods in the form of tax-paying farmland, towns and industrial installations. With drainage, forest clearance, and the conversion of so much land in the watershed to farmland, floods along the Mississippi became more and more pronounced in the twentieth century. Siltation from farmland widened and shallowed the river beds, which made floods more frequent and severe. By the 1920s the flood peak as far north as Minneapolis had risen by 40%, and the new landscape resulting from riverside drainage had to be supported by greater and greater expenditures of government monies in the form of levees, dredging, and other channel work. While dwellers in the floodplain profited from the development of their landscape, they could not afford to replace the natural services their development destroyed (in this case, flood control), and had to ask the federal government (that is, every inhabitant of the United States) for help. In 1927 floods along the Mississippi destroyed 160,000 homes and every bridge for 1000 miles upstream of Cairo, Illinois. This flood led to the federal government taking over the flood control system and developing modern schemes for controlling the river. Currently the costs of anyone living in a floodplain in the United States are paid for through federally supported flood insurance and river control projects.

In some cases, the human conversion of natural landscapes such as prairies and forestland to something of more immediate human value (logs, farmland, fenced grazing land) no longer seems economically reasonable. In the 1920s sportsmen argued against draining and leveeing swamplands along the Mississippi using the same arguments used today: that the value of the natural river was greater than that of the drained land created by levees. African pastoralist systems of keeping cattle are several times more productive in cash and protein per acre than western-style ranches (which consist of fenced private property) in similar dry climates; the unpredictable weather makes nomadism a more reasonable economic strategy. (But wild animals, such as gazelles, will produce three times the edible flesh of cattle on the same grasslands, and buffalo, together with their commensals mule deer, elk, pronghorn antelope and prairie dogs, will produce more flesh per acre than grass-fed cattle on the American plains.) The net income from forestry on good forestland can equal that of a farmer on the same land. If prices are good, the income from the furs and mushrooms taken from an acre of Middle Western oakwoods will equal what the land nets if cleared and planted to corn. (Gross income from the forest will be less, but the forester is less heavily capitalized than the farmer.) Sustainably harvesting mature timber (one white oak per acre every few decades) doubles or triples the yield per acre, letting the forester earn more than the farmer. The scheme works now because farm commodities are abundant, while wild mushrooms and good quality timber are scarce, so the price of forest mushrooms and timber is high and of farm crops low; and because modern transportation systems allow perishable goods like mushrooms to be marketed at a great distance. (As for furs, the price varies; some people consider wearing fur unethical and their influence, waxing and waning with the fashion world, can lower the price considerably. Fur boycotts helped put trappers of wild animals out of business. Most fur now comes from farmed animals.) Row crops net $50 to $100 an acre, one-tenth the value of a large white oak log. Since the log takes 150 years to grow, and will increase in value for another 150 years, and one might have 50 to 100 trees, or 100 to 300 logs, per acre, the potential incomes from sustainable forestry and row crop agriculture are not that different. Since the gross income per acre of the forest owner is so much less, his contribution to the total economy is also less. He receives no return for the clarity of the water that flows off his land, nor for his land’s value in storing carbon, nor for its value as habitat for plants, animals and pollinating insects. A problem with any scheme of sustainable forestry is that developing a stand of timber takes a long time and that at any time the stand can be cut for cash.

Medieval Europeans had more or less sustainable lives. For most of European history, peasants were poor; economic life in Europe went up and down (one can read such long-term cycles in the price of wheat) and the material life of an agricultural laborer in Europe in 1700 was little different from that of one in ancient Rome. One gets a hint of such lives from current peasant agricultures. In the western foothills of the Sierra da Estreda in Portugal, people still farm the sides of steep valleys, whose soil consists of an infertile clay eroded from Precambrian shale. The hillside soil is held in place by dry stone walls. Planting terraces are irrigated with water held in pits dug in the shale slopes above. The terraces are fertilised with shrubs cut from the upper slopes of the hills. The material is used as bedding for goats for two to four weeks, then piled up and let compost, and mixed with the soil of the terraces at planting time, at a rate of three to four tons (dry weight) per acre. Thanks to its time in the goat pens, the material’s decay is rapid. The compost provides nutrients and improves the water-holding capacity of the soil. The high shrublands (the mato) which provide the fertility for this system are cut on rotation every four years. One heath species is dug out by the root, and the root used in distilling alcohol from wine. Unless it were removed, this species would tend to dominate the heath, so removing it is important, since the different species of shrubs have different uses (besides compost; and probably in the ecology of the shrubland itself, which I assume is also grazed by the goats). Most of this work is done by hand.

Such a perspective makes it clearer how French and Scottish fur traders in the 1600s and 1700s could settle in to live with the natives with whom they traded; their material lives were not that different. Settlers in Massachusetts found the Wampanoag wickiup warmer and more weather-tight than their wood-framed houses. Venting smoke through a hole in the roof was no surprise to people coming from a land where the chimney was just coming into use, and who built their chimneys from sticks and mud. Indian mocassins were more comfortable and watertight than English shoes, their bows more accurate then English blunderbusses. The Indians’ diet was better: they were taller than the Europeans. The Spanish in 1500’s Florida could not pull the bows of the Timucuans. The bows were the thickness of a man’s arm and shot arrows at a rate six times faster than a harquebus or a crossbow could be reloaded. The arrows traveled 200 yards and split oak logs six inches thick. (Some of this may be exaggerated.) In the 1500s the natives in New England would not allow the Europeans to settle permanently, but only to trade, and after a few incidents of kidnapping, the Wampanoag killed most of the survivors of a French shipwreck on Cape Cod and enslaved the rest; and killed everyone on board a ship in Boston Harbor and burned the ship. But European diseases finally defeated them. An epidemic in 1619, probably of a viral hepatitus spread by food, perhaps from a survivor of the French shipwreck, killed 90% of the people in coastal New England, in a band 200 miles long by 40 miles wide, from southern Maine to Narragansett Bay. The Wampanoag thought their deities had failed them. The Pilgrims, ariving a year later, saw in the empty land the good hand of god. In 1633 a smallpox epidemic killed 35-50% of the remaining Indians in New England.

While their material lives may have been similar, the paradigms of European and Native American lives were utterly different. Most of the Native Americans in New England were horticulturists, but made much of their living from the forest’s mushrooms and furs. They weren’t that interested in accumulating wealth, especially at first, when their societies were still intact. (Status was another matter.) Wealth for Native Americans was found in the existing landscape. The Europeans’ advantages included their diseases (which in succeeding waves eliminated most of the native peoples); their metal goods, which the natives found useful enough to trade for; their domestic animals; and an uncompromising ideology of spiritual superiority and financial gain. The English in New England found the native men shiftless, since they spent so much time hunting and gathering, and not in the fields, which were worked by women. (In many cultures women give birth to children and plants.) An English philosopher argued that the farmer, by making the land more productive, usurped the rights of the aboriginal inhabitants; his labor gave him a superior moral right to the land. A difficult argument: should farmers then surrender their land to industrialists, who would further increase its value? (When paid for it, they did.) Most of the eastern Indians were horticulturists and crops formed an important part of their diet. Lacking domestic animals, they needed the animals of the forests, rivers and seashore to survive. The English soon adopted native crops and cultivation methods. Certainly clearing more of the land to grow corn made it possible to feed many more people, and once they had a foothold, the Europeans rapidly increased.

For a hundred years, until late in the twentieth century, the principal value of the redwoods and Douglas firs of California and the Pacific Northwest was found in cutting them down. These forests contained a greater mass of living tissue per acre (up to 500 tons) than tropical forests. Little thought was given to how the trees formed their particular riparian ecosystems, influencing the salmon streams that flowed through them, and the beaches and marine fisheries at their mouths. Logging the forest created value in the form of jobs, tax monies, profits for the timber companies. On private land, property taxes were partly determined by the value of the timber, and fell if the timber were removed. On government lands, some of the stumpage paid by logging companies funded local school systems. The cutover forest was replaced with planted forests of a single species, usually the fast-growing Douglas fir. After clearcutting the trees and burning the slash, the former woodland was sprayed with herbicides to eliminate the nitrogen-fixing broadleaved trees and shrubs that form the natural succession in these forests. Eliminating them and planting conifers speeded up the rotation. Under natural conditions, the nitrogen-fixing plants built up the stores of nitrogen in the soil, which would be exploited by the huge firs and spruces that succeded them. The trees would live on the banked nitrogen until nitrogen-fixing lichens appeared late in the succession. If possible (especially as the population grew), cutover private land was sold for building lots, because even with short rotation times (80 years for Douglas fir) and generous government subsidies, timberland, with a return of 2- 3% a year, cannot compete with other investments, such as the stock market (7-15%). Money made from timber or land sales and invested in the stock market would yield 10-11% a year over the long term; and the long term in the stock market is 10 years, not 80 to 150 (or 400 to 800, for sustainably managed old growth trees).

Various modern scenarios point out that the salmon, sea trout, mushrooms and other renewable products of the natural forest, together with some timber, harvested so as to maintain the watersheds and the structure of the forest are worth more over several rotations than the timber alone, harvested when it reaches economic maturity. The rotations here are very long in economic terms, with considerable valley bottom land and most steep slopes left in lightly thinned old growth: ideally, one would remove only trees that are not likely to survive until the next cutting cycle, while leaving some large dying trees to become snags. (John Muir proposed a sawmill limited to dead trees, a refreshing idea, if not quite as enlightened as it seems.) The sustainable forest would produce a more or less stable yearly income, rather than the boom and bust of the capitalist forest, with its clearcuts and periods of regrowth. In general, sustainable models of using renewable resources produce no net overall growth, but of course neither do capitalist models of a given resource, which produce bursts of growth followed by long periods of decline, and which often end with the permanent extinction of the resource. (Growth in the economy as a whole comes from investing the profits of resource extraction elsewhere.) With forests, prices for timber can rise and new uses found for forest products, so the value of what is produced can rise, but the amount taken from the forest remains the same.

A major difference between the capitalist and the sustainable models is time. The long term in the capitalist model is the time between quarters; or a decade of market returns; or the time taken to liquidate a resource, whether oil or timber (a month, 5 years, 20 years). Factories such as paper mills are built to cover the lifetime of the resource. The longest term for an individual investor is a human lifetime (80 years, perhaps 40 or 50 of that spent working); after that, as Keynes pointed out, we are dead. The long term in a natural environment is the life of the ecosystem. What matters here are things like the rate of soil formation and erosion, the likelihood of volcanic eruptions, the speed of climatic change. The lifetime of a north temperate landscape like the Pacific Northwest in our glacial epoch is probably somewhere between 10,000 and 20,000 years. (Tropical ecosystems last longer, but nowhere near mountain ranges, whose lifetimes average 70 million years.) The current ecosystem in the Pacific Northwest is between 7,000 and 10,000 years old. So this is the age of its soils, created out of glacial dirt by its generations of trees. (Say, 70 to 100 generations at 100 years each, or perhaps less: the age of senescense in old growth Pacific Northwest trees ranges from 300 to 800 years for Douglas firs, pines and Western red cedars, and up to 2000 years for redwoods and sequoias; but the trees start reproducing themselves at younger ages, and so generation time is less than this.) This is longer than any human “high civilisation” has lasted. Apart from timber, the renewable products of an old growth forest include salmon, trout, furs, mushrooms and recreational space; its services include water storage, water filtering and carbon sequestration. All this might be worth $100 to $200 an acre a year. The lower number is too low, but unless the landowner runs a hotel or collects mushrooms himself, most of the potential income from the land goes to outfitters, bed and breakfasts, gas stations, motels and restaurants. In a world that valued sustainable uses, the landowner would receive income from licenses and leases. Farmers in Costa Rica receive annual payments for maintaining and restoring their forests. The payments are related to the forests’ value in reservoir maintenance (less silt to fill the reservoirs, more even water flow for power generation), carbon sequestration and tourism. Over a rotation of 300 years, $100 an acre comes to $30,000. During this time, the timber, harvested regeneratively—I am assuming this is possible—has a stumpage value of $15,000 to $30,000. The total ($45,000 to $60,000) is in the range of the stumpage value of an acre of 300 year old trees, clearcut. The numbers are comparable, but the money comes from different sources, and steadily, rather than in widely spaced increments. Because of the hand labor involved in sustainable management, many more people would be employed. (Sustainably managing a fully stocked, 100 acre woodlot in the Canadian Maritimes, including sawing the logs onsite, would employ four people fulltime.)

Numbers change as markets vary. Both old growth timber and wild fish have increased in value as they have become scarce. In 2000, some acres of old growth timber were worth more than $100,000 in stumpage value (what the logger pays the landowner). On the same acre the annual mushroom harvest might be worth $60,000. Truffles worth $60,000 per acre wholesale (600 pounds at $100 a pound) are harvested from some conifer forests in the Pacific Northwest. (In the 1990s the value of the commercial mushroom harvest in Washington and Oregon was about $40 million annually, approaching that of the tree harvest.) If the truffle harvest is renewable at half this level, licenses to harvest truffles, or the truffles themselves, would be worth a fortune. (It’s the same story, though on a lesser level, with mushrooms, ginseng and other collected wild plants in eastern forests.) Truffles are characteristic of old growth forests. They are a major food of forest voles, which maintain the planting by spreading fungal spores in their droppings; the voles are a major food of the endangered spotted owl. If it were clear that managing forests for a steady source of income would produce a wealthier, more stable local economy, managing public lands sustainably would be justified. Private lands, insofar as their management interfered with a public good, that is, the health of the ecosystem, could be forced into sustainable management; or sustainable management could be made more worthwhile by compensation for the value of the water that runs off the land or for the land’s storage of carbon. The time involved in a rotation is a problem; perhaps landowners could get loans against the streams of revenue from their mushrooms, water and trees, at least 50 year ones: tree futures. Then one would have to thin the forest every so often. However the fact that costs and prices now work out cannot be the chief argument for using landscapes sustainably, because both may different tomorrow.

Modern human occupation of a landscape almost always results in its degradation. Ecosystems are landscapes characterized by conservation of nutrient flows; the flow of nutrients within the system (that is, the number of times each element of nitrogen or water is reused) is several times greater than the flow of these nutrients across its boundaries. The notion is a bit hazy in nature; where to draw the boundaries may be unclear. Movement of nutrients occurs mostly through the enveloping fluids of water and air, but animals also move between ecosystems, carrying nutrients, seeds and other propagules with them. Bacteria and other single-celled organisms, fungi, and small invertebrates in the soil and water for the most part manage the webs of nutrient conservation and re-use. Such organisms live in the shelter of the large organisms that define landscapes: trees, grasses, kelp forests, coral reefs. The structural organisms are affected not only by the microbial and invertebrate life of the soil or sea (whose habitats they create), but by other organisms that live on or about them, such as the burrowing rodents that reshuffle soils, grazers like buffalo, tree-breakers like elephants, nitrogen-fixing termites, browsing moose, seed-eating mice, leaf-munching and pollinating insects, insect-eating birds. Large herbivores create their own landscapes. In some African ecosystems, elephants alternate with grazers like wildebeest, or more recently Maasai cattle, the grazers leaving behind developing stands of brush and trees, the brush-eating elephants leaving behind grasslands. All these organisms also have their own predators and parasites. The water that flows off an undeveloped landscape has a chemistry determined largely by the soils and biology of that landscape. Biological life changes soils; the mineral earth, deposited in much of the temperate region by melting glaciers 15,000 to 20,000 years ago, was only the beginning of the story. The biological landscape also helps determine the total runoff of water (forests intercept 50-66% of total rainfall and return it by transpiration and evaporation to the atmosphere); the water’s temperature (shading influences the temperature of streams); and its timing (whether streams rise quickly, or more slowly, how long perennial flows last).

Human settlement interferes with all this. The effect of something like farming on a landscape is clear and enormous; crops replace forests and prairie; insects of cropland (orders of magnitude fewer in variety) replace those of the forest; mammals, amphibians, reptiles, birds are different, mostly gone, replaced by those that can survive in fragmented habitats, and by farm animals and pets. The nutrient-conserving web of organisms is broken apart and the land sheds nutrients and soil into ditches and streams. Even under ideal conditions, farmlands shed nutrients; during heavy rains or with cool spring temperatures the simple biological systems of a farm let nutrients slip through.

Settlement also changes micro-climates. Without the shelter of the trees, the land’s surface warms more quickly, freezes more deeply, dries out more thoroughly. Wind speeds near the ground increase. Water tables fall and springs dry up, the latter a common complaint of settlers in the Northeast and Middle West. Rainwater on the prairies filtered down hillsides into sloughs, then into perennial streams; after the slopes were plowed, the water ran off quickly, the sloughs dried in the sun, and the streams ran only after rains. Cleared ground holds less rain or snowmelt, thus less water goes into groundwater recharge, which feeds springs. The exposed snow melts more rapidly, and so water runs off faster and in larger amounts, carrying more soil particles and nutrients into streams. Summer flow is lower. Deforestation in the eastern United States typically increases total water yield 20-40%. (In the Rockies, forested watersheds have been cut in specific patterns so as to yield more water for storage dams.) So the spring pulse of meltwater is larger and earlier, summer flow lower and warmer. The bacteria, algae, zooplankton, invertebrates, and fish that inhabitated the stream were adapted to the temperatures and flows of the old environment; they may survive the new regime or they may not.

Virtually every physical, chemical, and biological aspect of surface water affects fish and their insect and planktonic prey, as it affects their habitat among the rocks, logs, mud, and gravel of the stream bottom. Addition of more material with more settlement (nutrients, hydrocarbons, metals, sewage, topsoil, fertilisers, pesticides) increases the stress on the organisms in the streams. Dams change rivers’ flows as well as their water temperature and chemistry. Riverside wetlands store much of the spring floodwaters and release them non-simultaneously, thus maintaining stream flows. Such wetlands also trap about 80% of the sediment entering a river and turn it into land. Drainage ends this. All changes in the landscape propagate downstream, where in the flatland reaches of large rivers the size and timing of the spring pulse and the level of summer and fall flow is crucial for the breeding success of many species of fish. Further downstream, in ocean estuaries, the size and timing of the water pulses and the strength of seasonal flows, along with nutrient levels, help determine the breeding success of many species of marine fish, about two thirds of which spawn in estuaries. For each dam that was built, and each riverside farm that helped destroy a natural river (and the estuary it helped feed), the human construction seemed worth so much more than the fish; but as all the rivers were dammed, and as more and more farms and cities were built along them, there would be no more abundant fish.

The changes in rivers, lakes and the ocean associated with the development of modern landscapes are not small. In one of those brutal, useful scientific demonstrations of the middle years of the twentieth century, two scientists clearcut a mountainous New Hampshire watershed, treated the vegetation with herbicides to prevent regrowth, and studied the effects on the movement of water and nutrients through the system. Flows following summer rains increased three to four times, and the warm, respiring soils of the watershed released enough nitrogen into the streams to kill trout. Siltation increased enormously. Erosion rates in logged forests are about 500 times those in undisturbed ones. Rates drop slowly as the forest recovers. Landslides occur on the steep slopes of western forests three to five years after clearcutting as the roots that held the slope together rot away. Insignificant rains set them off.

All this of course was known, if not in a proper scientific sense. In the eighteenth century, wharfs at river mouths along the Connecticut shore of Long Island Sound had to be extended 1000 feet or more into the sound because of siltation caused by land clearance upstream. (The wharf extension reached 3900 feet in New Haven harbor in 1821. Some of the extensions were the result of larger ships needing greater depths of water.) Tidal areas of San Francisco Bay were raised several feet by silt washed downstream from gold mining in the Sierras in the 1850s. Hydraulic mining, which used water pressure from channeled streamflow to remove whole hillsides, generated enormous quantities of material. The sediment filled the bay’s coastal marshes and ended the bay’s oyster fishery. The bed of the Sacramento River was raised 10 feet and the city of Sacramento flooded. Riverside farmland also flooded. About 6000 square kilometers along the Yuba River was buried in mine spoil. The last two events led to the banning of hydraulic mining, though only when most of the gold was gone. Much of the salmon-rearing habitat in the Sacramento basin was destroyed. Some Sierra streams accumulated 100 feet of sediment and are still cleaning themselves out today. In the 1880s canneries put up 200,000 cases of salmon a year, about 10 million pounds of fish, from the Sacramento watershed north of those destroyed by mining. That much salmon would be worth $100-$200 million at retail, as fresh fish, today. (The value of the sport fishery would be more.) Miners removed 700 tons of gold from the Sierras, worth $1.5-$2.0 billion at today’s prices, that is, 7 to 20 years of salmon. They used 7000 tons of mercury to do this. Much of the mercury ended up in San Francisco Bay, where 150 years later it still makes the fish unsafe to eat.

In northern oceans, single-celled plants called diatoms make up 80-90% of the spring algal bloom and 50% of the annual phyto-plankton production. They leave a record of their lives in their silicaceous shells, which accumulate in sediments. Cores taken from Chesapeake Bay in modern times indicate that the bay’s diatom population was changing by the 1760s. Diversity was dropping and the organisms left were characteristic of turbid water. The rivers that fed the presettlement bay were said to run clear, even in high water. (This may be an exaggeration, but it is something one would think Europeans, used to their turbid streams, fed with agricultural silt, would notice.) Native Americans had thousands of acres of cornfields in the valleys of the rivers feeding the bay and tens of thousands of acres of fire-cleared grassland. Early Euro-American agriculture in the Chesapeake region mimicked the native hoe culture, but was a commercial agriculture using slaves and indentured servants for labor. Corn and tobacco were planted in small fields among the trunks of girdled trees. Fields were not squared off, but followed drifts of suitable soil. Crops were fenced to keep out the cattle and hogs that roamed the woods. Fields were used for three years, then let return to forest. Only the best land was used; perhaps 2% of the land was in cultivation at any one time. Cultivators were aware of the dangers of erosion. Since crops were shipped out by water, and dredging was expensive or impossible, siltation and shoaling of rivers was a serious matter.

Tobacco was the first cash crop. It was extremely profitable. In Spanish colonies in the West Indies, tobacco, grown with slaves, returned six times the value of any other crop. In Virginia the tobacco tax returned to England four times the revenue the Crown received from its colonies in the West Indies. But tobacco needed a constant supply of new land. After the 1720s, as settlement increased and more land was cleared, wheat began to be grown for the New England market. Cultivation of wheat meant draft animals and plows, permanent fields, permanent pastureland, shorter fallows, use of manure from penned animals on the crops, more water and soil running off the land. Pasturing animals in the forests, in the old style, also resulted in erosion and soil compaction. Using the forest as pasture will eventually turn it into a woods of scattered trees, with very little reproduction. (Some protected ancient woodlands in England are of this sort.) By the 1750s, rates of water runoff into the bay following rainstorms were several times natural levels and summer anoxia in the bay was growing. Some summer anoxia in the bay is natural, caused by warm fresh water from the rivers flowing over cold salty water brought in on the tides from the ocean. Agriculture caused widespread siltation of streams by the 1770s, with shoaling in the rivers feeding the Upper Bay. Riverbeds rose by tens of feet. By the early 1800s perhaps 40% of southern Maryland was in cultivation. Sedimentation in the bay probably reached its height in the late 1700s and early 1800s. The silt brought by the rivers reduced the bay’s water clarity, a critical characteristic of the presettlement bay. The additional nutrients from runoff fed planktonic algae, which also made the water turbid. Before European settlement, much of the bay’s productivity was channeled through its seagrass meadows, which removed silt and nutrients, provided shelter and breeding habitat for fish and invertebrates, and served as food for waterfowl and other wildlife. The meadows depended on high levels of light. By the 1780s water runoff rates, accelerated by forest clearance and agriculture, from parts of the bay’s drainage are estimated to have been 20 times natural levels, while sedimentation (the build-up of mud on the bottom) had probably risen two to four times. Over the next two centuries the watershed of the Potomac River went from 80% forested to 20% forested and the soil carried by the Potomac increased eight times. (While the total watershed of the bay has recovered from 20% forest to 40% forest at present, much of the forest is very fragmented. Sediment carried by the Patuxent River to the bay went from 160,000 tons in 1950 to 710,000 tons in 1980, corresponding with a 21% further removal of forest in that river basin.). Nitrogen entering the bay increased four to eight times, phosphorus 10 to 30 times; the nutrients fueled tremendous algal growth. Silt smothered the oyster reefs and the seagrass beds, which both eventually declined by 90%. Oysters are filter feeders that remove plankton from the water. In 1500, oysters were sufficiently abundant to filter the bay’s water every three days. They were a major factor in keeping the water clear. Oysters were also overfished. Dragging for oysters slowly removed their reefs, which were useful as settling points for young oysters. Reefs were also dredged to clear shipping channels.

Fish runs were declining by the middle 1700s, probably largely from habitat change caused by settlement. Silt from eroding fields infiltrated the spawning beds of river gravels and smothered developing eggs. Higher stream flows after storms scoured out eggs and larvae. Higher water temperatures and lower summer flows made the rivers less habitable for fish. Chesapeake Bay is the drowned estuary of the Susquehanna River. When the Susquehanna Basin was fully forested, peak flows in the river would have been 25-30% lower, summer base flows higher. Much of the summer river would have been cooler. Many of the bay’s fish are anadromous, that is, sea fish that spawn in fresh water, go through a juvenile stage there which lasts from one to several years, and return to the sea to mature. These include river herring, sturgeon, striped bass, perch, alewives and shad. Before the rivers were dammed, river herring ran up the Virginia rivers to the Shenandoah Valley, and up the Rappanhannock and James to the Blue Ridge. Small mountain streams had fish returning from the sea. Shad ran up the Susquehanna to Binghamton, New York. There was a shad fishery on the north branch of the Susquehanna in Wyoming, Pennsylvania. (The Susquehanna had perhaps 1500 miles of shad spawning habitat.) Commercial fishing began in the Chesapeake in the early 1800s and peaked in 1833 with an estimated 750 million river herring and 25 million shad salted. Both catches would be reduced by 99% by 1878 (and then recover slightly), partly from overfishing, partly from dams, partly from the deteriorating condition of the rivers, which would no longer support spawning fish or their juvenile offspring. Such losses would have repercussions throughout the habitat. (In Long Island Sound, the population of alewives, a major forage fish, is now at 3% of former levels, largely because dams on the rivers and streams feeding the Sound have eliminated its spawning habitat. Predatory fish like striped bass and swordfish and birds like ospreys all depend on fish like alewives.)

The abundance of plants and animals in the new world bewitched the Europeans. Thomas Morton, an affable English opportunist, described the gastronomic pleasures of the turkeys, geese, swans and shorebirds in early New England, which he shot more or less from his yard. (The image of a man with a gun, setting off into the wilderness, so quintessentially American, seems to have been an English one. Morton also scandalized the Puritans by setting up a maypole and dancing around it with the few remaining natives, and trading rum and firearms to them for furs. In the end the Puritans jailed and fined Morton, burned his house to the ground, and drove him out of Massachusetts Bay and back to England, where he wrote his memoirs.) The abundance of wildlife lasted for some time. Markets in American cities were full of game until the 1890s, when the age of wildlife abundance ended in the West. It had ended in the East forty years earlier. Center-fire cartridges, repeating firearms and fast refrigerated transport by railroad disguised the falling abundance of game animals and made the 1880s the golden age of the market hunter. As market hunting declined, hunting continued at a local level. White-tailed deer were virtually extinct in much of the Northeast by 1900 (in Vermont by 1840). The abundance the Europeans saw may have partly been the result of the depopulation of the country by European diseases several decades before Euro-American settlement took off (thus the rebounding of populations of game animals no longer hunted), partly the creation of a more varied landscape in the early days of settlement (more environment of the edge), partly the enduring emptiness of a large part of the continent. European fisheries had been as abundant several hundred years earlier, when fish were caught in traps or with hook and line; the invention of the trawl, along with the settlement boom after the year 1000, began their decline.

In North America, the Europeans were interested in what was marketable; their new landscapes produced not game, fish and clean water, but crops like tobacco, corn and cattle; goods like firewood, potash, sawn lumber, water-power for mill dams. Dried fish and salt beef were sold by New Englanders in the 1700s to markets in southern Europe and the West Indies. The excess fish catch was fed to pigs and used to fertilize fields. Oak staves for making sugar casks were also in demand. The most profitable use of New England timber was for building ships, used in the triangle trade for slaves and rum. (African slavery was not new in 1500 but plantation agriculture in the New World increased the worldwide demand for slaves. Some writers suggest that the introduction of peanuts, manioc and maize to Africa from South America in the 1500s let African populations increase sufficiently to meet the new demand for slaves.) In the capitalist world of the 1600s and 1700s marketable resources turned into capital, which turned into other goods. As profits from an enterprise fell, investment moved elsewhere. Fields were abandoned as yields fell; or went into long-term fallow. Tobacco and corn farming were always considered migratory occupations in much of the South, where animals were rarely penned, making their manure unavailable. In Virginia low ground or bottomland was planted to corn, for food for animals and slaves. The land under upland hardwood forest, regarded as more fertile, was used to grow tobacco. Trees were girdled and tobacco grown among the dead trees for three years, then wheat for two or three, then the land was abandoned; such land usually succeeded into pine forest. (Thus the “piney woods” of the South, a modern creation.) By 1800 much of coastal Virginia and Maryland was gullied, abandoned farmland. By 1817 North Carolina had abandoned land equal to that under cultivation. Breeding slaves for the new lands to the west competed with crops as an agricultural enterprise. The increasing value of the human crop helped lead to the Civil War. Tobacco is a nutrient-demanding crop, needing 10 times the nitrogen and 30 times the phosphorus of other crops, and cannot be manured (manure ruins the taste). It was thought for a long time tobacco needed the nutrients in newly cleared ground. While loss of nutrients is one problem, after a few years a build-up of nematodes and a fungus in the soil also stunt the tobacco plant’s growth. Controlling the fungus requires a very long fallow.

Many attempts at using the new lands went awry. Some landscapes, such as upcountry New England, or the American plains beyond the line of reliable rainfall, should never have been settled with traditional European crops and animals. The hilly uplands of the Piedmont South had a boom in cotton after the Civil War. Newly discovered phosphate deposits along the South Carolina coast, whose cost was half that of Peruvian guano, together with wide-row cotton culture (the crop was cultivated with mules), led to excellent crops, but also to enormous erosion from the Piedmont’s coarse soils. Cotton responded well to phosphorus but its use led to nitrogen depletion (German potash and nitrate helped here), which reduced yields, so more and more land was brought under cultivation. While the use of fertiliser led to good crops, the cost of the fertiliser made the crop barely profitable to most farmers. Some farmers rotated cotton with a combination of corn interplanted with cowpeas. The cowpeas helped maintain soil fertility, improved soil structure and reduced erosion in the corn; people and hogs ate the corn and peas. This would have made the whole system more sustainable. But few farmers performed the rotation, since it took land away from cotton, the cash crop. The eroding soil raised streambeds, creating swamps behind the rivers’ natural levees on former river bottomland. Fertile riverside fields thus became swamps, especially in areas of low gradient. The sediment depth in some Georgia bottomlands reached 3 feet, while riverbeds rose from 3 to 17 feet. In general American agricultural practices have caused the loss of about 6 inches of topsoil per century (say, 12 inches to date), with the soil ending up in lowlands, rivers, the sea. The loss in the Piedmont was similar but more rapid, since many Piedmont soils gullied spectacularly. (Some gullies inspired tourist visits.) Piedmont soils in Alabama and Georgia had probably always been forested and at the time of American settlement had evergreens 2.5 to 4 feet in diameter, 120 to 320 years old. These trees grew without fertilizer or care. One can tell a similar story about much Appalachian farmland. By 1979 about 100 million acres, 17% of U.S. cropland, had been ruined for commercial agriculture.

Economic development of the landscape during the settlement of the United States focussed on creating additional real estate value. Much development was anachronistic or pointless. Rivers were destroyed by canals going the same way as the railroads that would replace them. Rivers today continue to be turned into waterways, since with the state providing a straightened, dredged stream; dams; and locks, river transport is cheaper then rail. Large barge tows can carry more than fully loaded coal trains, the most massive land transportation device, and cheap transportation makes low-value goods such as timber and grain more marketable. Once river ports develop, the value of their real estate must be protected, which leads to more development of the river. Settlement continued in river flood plains long after there was any economic purpose in being near the water; here also, new development supported previous development. Politically it was easier to control the river than to move the people. The capacity of developed and abandoned landscapes to produce timber, game, fish, row crops or grass, or to conserve and recycle nutrients, was permanently (in human time periods), reduced. Given time, and especially in more humid regions, such lands would recover, though now set on a different trajectory. (Degraded cropland and abandoned strip-mines can also be regarded as an economic opportunity: places to set up arrays of solar panels, or electricity-generating windmills, to build houses and factories, to rejuvenate soils with carbon-storing crops.)

Abandonment and rebuilding is part of the capitalist cycle; it is the response to changes in demand. Some of this change is driven by technology. Thus the automobile made all previous commercial construction in the United States obsolete. Nineteenth-century downtowns were built for a volume of people who walked or took public transportation. The trams or cabs of public transportation were always moving; city construction didn’t allow for room to store the private vehicles of the same number of shoppers. When public transportation systems were abandoned in the automobile boom of the 1950s (many of them were bought up and let deteriorate by automobile companies), urban downtowns couldn’t deal with the number of cars. Commercial activity moved out to the suburban edge, and urban downtowns, more and more inhabited by the less well off, were left to decline. (Urban housing typically takes many decades to decay and falling rents make such places desireable for a long time.) New development always moves toward cheaper land, which is less developed land. And cheaper land tends toward development, in an attempt to make itself more valuable. Development is partly pushed by property taxes, a major cost of holding land, and partly by the return from land trying to keep up with returns from money invested in manufacturing or the stock market. Unless they are protected, it is the ineluctable fate of all private lands in a capitalist economy to be developed. (So one can predict the fate of an abandoned apple orchard in Fairfield County, Connecticut, which birders identify as a stopover site for hawks on their long slide south, where the birds rest and pursue grasshoppers, dragonflies, meadow voles and starlings; or of the scattered clumps of pine trees among farmland in the narrow neck of southern Mexico that local farmers point out as the places migrating hawks roost.) With development, lands lose much of their biological value; if polluted, they acquire a negative biological value. Abatement of a public nuisance is the owner’s responsiblity, so polluted lands are expensive to redevelop, since they first must be stopped from leaking toxic materials to the atmosphere, into peoples’ lungs, and to waterways. (Abandonment is the simplest solution, though more difficult nowadays.) Developed, polluted landscapes are the natural result of capitalism left on its own. Since capitalism always seeks the lowest-cost solution, there is no economic benefit in taking account of the value of a natural ecosystem; none in not using dangerous materials if they are the least expensive (especially if one has constructed a factory to make use of them); none in not disposing of waste products as cheaply as possible.

Values change with development and also over time. Everyone knew that building dams on the rivers of the Pacific coast would eliminate the salmon. (The effects of logging, farming and mining were less obvious. But in the 1860s the Chimariko Indians, who depended on the salmon runs, fought battles with local gold miners over the color of California’s Trinity River, its clarity gone thanks to mining operations.) Currently the income that would be generated by the run of salmon and sea trout in a river like the Elwha on Washington’s Olympic Peninsula is probably worth more than the electricity generated by its dams. Dams commodify rivers, turning the energy of the moving water into private or state property, and making the stored water saleable, while eliminating the fish that were free to everyone. The first dam on the Elwha was built on speculation. It was built without fish ladders, which was then illegal: to compensate for the loss of spawning area the owners built a hatchery. The hatchery never worked and was abandoned. The Elwha flowed through old growth forest and the electricity from the dam made it possible to set up a paper mill. Another dam followed, also for the mill. At that time, the company payroll was probably worth more than the fishery. (The Elwha’s run consisted of perhaps 250,000 fish, of all 5 species of Pacific salmon plus sea-run trout, say 2.5 million pounds of fish, about half harvestable on an annual basis. The dams eliminated much of the fishery and violated the spirit of a treaty with the local S’Kallam tribe, which guaranteed them rights to the Elwha fisheries.) But numbers change. The electricity generated by dams on the main stem of the Columbia is now worth about a billion dollars a year. In the eighteenth century 50,000 Native Americans along the Columbia caught 20 to 40 million pounds of fish, which amounted to 5-20% of the run of 11 to 16 million fish (100 to 800 million pounds of fish). Taking up to half a salmon run is considered a sustainable harvest. If one could harvest, on average, 100 million pounds of fish, the salmon run would be worth $1 to $2 billion dollars at fresh retail, half that wholesale, a third of a billion dollars at retail if canned. Depending on one’s calculations, the fishery might be worth more than the power. Dams of course have to be rebuilt, while a natural river maintains itself. (Dams are designed to last 250 years but need major renovations every 25 to 50 years. Such costs are not subtracted from the value of the power.) Electricity generation however subsidized the river’s development for irrigation, ship traffic and water supply. Without cheap power, and an aluminum industry that could use it, and aircraft manufacturers to use the aluminum, how would the Pacific Northwest have developed? One could argue that it was economic development, made possible by electric power, that made fresh salmon worth so much. We could also ask why electric power and aluminum should be so cheap; and whether rivers and their landscapes must be developed so as to destroy their natural functions. Could we not use rivers in a different way?

Sailing west to Greenland in the year 1000, the Norse recognized they were passing south of Iceland by the pods of blowing whales to the north. Similarly, the Pilgrims sailed into Cape Cod Bay through schools of whales, arriving in a land that depended on corn, beans, beaver, white-tailed deer and fish. Runs of Atlantic salmon were smaller than those of the Pacific Coast. Perhaps 2.5 to 5 million Atlantic salmon returned to rivers in the northeastern United States and Canada. But the Atlantic Coast of North America had several other abundant species of anadromous fish. Fish provided a third of the calories for many tribes and much of their protein. Early observers may have mistaken the silvery, spring-running shad for salmon. By the late 1600s the blocking of fish runs by dams was an issue. Riverside farmers put up fish for the winter; food was a major expense. The modern world lay in the future. Colonial legislatures passed laws requiring dams to be removed during fish runs or modified to let spawning fish pass. Existing dams were exempted. Such laws were known from England, where dams on salmon rivers were required to leave gaps wide enough to accomodate a well-fed 3-year-old pig. These laws were widely ignored, though less in New England than in the Chesapeake region, or later, on the Pacific coast. In the early nineteenth century Boston capitalists dammed the main New England rivers to provide year-round power for their textile mills. No modern businessman was going to open a dam for a month to let spawning fish pass. So-called salmon stairs, which were invented at about that time in Scotland, which would have worked with such low dams, and which were not considered expensive, were not installed. So the fish runs ended. By 1850 half the potential salmon habitat in eastern North America had been closed off by dams. Today 900 dams block New England salmon rivers. In the latter part of the nineteenth century logging was fought over as its effects on rivers became clearer. New York State’s Adirondack Park, the largest park in the United States east of the Mississippi, was established partly to preserve a potable water supply, the Hudson River, for New York City. (The upper Hudson was already shoaling from two centuries of agriculture in its hinterlands.) Preserving the Hudson’s flow did not stop the State from allowing its pollution. New York has never tapped the Hudson, but uses the nearer Catskill drainages, also turned into a park, for much of its water.

A general definition of a capitalist society is one that is able to mobilize capital, or its equivalent, to accomplish some remaking of the world (an irrigated field, a dam, a mine), that produces a profit, that is, a surplus, for the society. Socialist and communist societies and chiefdoms are capitalist in this sense, differing in how they collect and allocate the profits. (Economists will not like this unrigorous definition.) In general, capitalist societies have not managed renewable resources well. They are not to be blamed for this; their focus is on the human; and most capitalist economic doctrine essentially eschews renewable management, instead managing resources to economic depletion. (Modern so-called stakeholder capitalism tries to take the needs of the owners, the workers, the local community, the nation and sometimes the larger ecosystem into account.) Virtually no federal forestland in the United States has been managed so as to recreate, over time, its original biology and structure, or to protect the streams and fisheries which its landscape shelters. The timber has been cut as fast as the market would allow, or as the timber companies demanded, in the interest of maximizing short-term profit and community development. When the trees were gone, the timber towns (like river or mining towns) were finished, and their real estate values declined. Timber companies followed the trees elsewhere and loggers (stuck with real estate of little value) blamed environmentalists for their problems. Lots of schemes have been put forward for the renewable use of tropical rainforests: collecting gums, nuts and fruits; collecting medicinal herbs; “sustainable harvesting”of the timber (which may or may not be possible in that environment); raising iguanas for meat on the forest edge. But the value of the trees is too great. Estimates of the value of the timber in the Amazon basin range from $3 to $5 trillion dollars. This may be too high, given the amount of clearing to date, and that Brazil’s legal cut in 2004 was only worth $1 billion (though illegal cutting might double or triple that), but a value of $1 to $3 billion dollars a year, some of which goes to feed very poor people, means the timber will be cut, even if, as seems likely, cutting the forest will change not only the soils but the rainfall regime (one half or more of the water that falls on the Amazon basin is recycled from the forest itself), and thus make regeneration of the forest, especially in a warmer, drier world, impossible. (Elimination of the forest will also reduce rainfall in the savannahlands of the Cerrado, the immense and profitable agricultural region south of the forest. Such considerations make it seem Brazil would do better to try to eliminate poverty by other means, perhaps by redistributing its wealth more vigorously.)

The world is now capital-rich. Capital could be found to preserve the Brazillian, Indonesian, and African rainforests (all with huge stores of carbon in their plants and soils), as well as those remaining on the west coasts of Canada and the United States. The aboriginal population of the Amazon has been estimated at four million people (several times the current population), but such estimates continue to grow. Amazonian communities were dense, and vulnerable to European diseases, and most of the population disappeared shortly after European contact. It is thought their survivors formed the scattered hunting and gathering tribes now found in the Basin. While settlement was concentrated along the rivers, more and more signs of dense settlements are being found in places between the rivers, together with more and more areas of terra prieta, the fertile black earth created by human manipulation hundreds of years ago (mostly by the addition of slowly charred wood). The Amazon rises 40 to 60 feet during the wet season and its falling waters leave tens of thousands of hectares of land available for cultivation. Some of this has been developed for rice cultivation. Much is used on a small scale for grazing water buffalo. Whether riverside and terra prieta agriculture, sustainable fishing, and the gathering of tree gums and fruits in a manipulated forest, in an economy connected by river transportation, would support a modern rural population as large as the aboriginal one, and one with a reasonable per capita income, of say, $2,000 to $4,000 a year, is another matter. (Currently 80% of the population of the Amazon Basin is urban. Two million people live in Manaus, a duty-free port with a thriving industrial sector.) In the case of the forests of the Pacific Northwest, over the remaining life of the ecosystem (perhaps 12 Douglas fir lifetimes) the return from the landscape would be greater (two or three times greater?) if it were managed as a whole functioning ecosystem, for timber, mushrooms, hunters, naturalists, tourists, electricity, irrigation water and fish, rather than for timber, river navigation, irrigation water and electricity alone. But the return for the national economy (not just that from the forest) would be less in the short term, since it would be deprived of the flood of income from clear-cutting. Rather than maximizing the return per acre over the short term (so as to efficiently deplete the resource base and accumulate a large amount of capital), sustainable management would manage a variety of interdependent sources of income over the long term so as to provide a steady annual income, with reliable employment.

Sustainable development anywhere would be preceded by a period of growth, as the infrastructure for it (solar panels, selectively harvested forest farms) is put in place. Then such growth disappears. A difficult idea, especially if the human population continues to grow, and if the point of life, as an old French text claims, is to become rich. (Without that goal, the authors claimed, man loses hope.) Indeed, without growth, how will capital grow? The yield from a sustainably managed landscape might be 2-3% per year, about equal to inflation. The stock market deals in minutes and quarters, and returns on investment, say, in land, are supposed to be paid back in a length of time considerably less than a biologically appropriate timber rotation: 150 to 500 years for many eastern forests, 300 to 1000 years for those of the Pacific Northwest. Even short-lived trees live longer than people. There have been 100 tree generations in eastern Canada since the glaciers retreated, but several hundred human generations. Business loans are short-term (3 to 10 years, sometimes 20). Government-supported loans to farmers with low interest rates and long repayment times are a concession to the limited returns that are possible from cropland, even under modern chemical management, where the soil lost from the fields outweighs by several times the grain, compared with investments where the rate of output is under better human control, such as mines, factories and office buildings.

Part of the problem of capitalist land management is its success, and therefore its scale. Developed landscapes now dominate many environments. So-called “high civilizations,” faced with growing populations, continue on and tend to create environmental problems that are outside of their control. The Sumerians knew that irrigation was causing saltation of their fields; under the pressure of a growing population and military rivalry among the cities of Mesopotamia, they substituted more salt-tolerant crops and brought new land under cultivation. The Hohokum who lived along the Salt River in Arizona had similar problems. In a more limited landscape, their solution was to keep rotating their fields, using only 10% of their cultivable land at any one time; fields were used for a maximum of 10 years. When the water table became too high and salts too pervasive, the land was retired. The Hohokum supported 100-200,000 people in the Salt River valley for 1500 years on irrigated agriculture and plantations of agave in the uplands, and were probably eliminated by European diseases. Ancient peoples were no less intelligent than we; moderns are abandoning irrigated land as fast as it is being created for the same reasons (saltation and waterlogging) as the Sumerians and the Hohokum. As long as new land is available, reclamation is not thought worth the investment. The Sumerians lasted 1000 years, until the new land ran out, and a long drought lowered the level of the Euphrates, and probably increased its salt content, and their problems overwhelmed them. We have used the fossil fuels that make our lives possible for 150 years. Economically recoverable oil was probably half gone in 2000. Coal should last 400 to 500 years more. We do very little about the problems fossil fuels are causing. The reasons to shift to other energy sources are not only ecological.

* * *

From 100 to 40 million years ago the planet had no permanent ice; sealevel was 70 meters higher; trees grew in Greenland and Antarctica despite the midwinter darkness. About 35 million years ago, the earth began to cool and enter the modern age of glaciers. Perhaps 20 million years ago large herbivores shifted from eating leaves to grass, grasses developed the ability to reproduce vegetatively by tillers and rhizomes, and ecosystems of carbon-storing grasslands and grazers became major components of the earth’s landscape. For the last several million years ice ages and interglacials have alternated on the planet. Of the last 2.5 million years 80% have been spent in glacial periods. The primary reasons for this climatic alternation are thought to be astronomical: variations in the earth’s orbit about the sun and thus in levels of solar radiation reaching the planet (periodic variations in the strength of the sun, that match the astronomical cycles, have also been suggested); but the fact that such small changes in sunlight (the variation is on the order of 8-9%) causes such dramatic climatic changes has to do with the amplification of the effects of solar radiation by the carbon dioxide, water vapor and other greenhouse gases in the atmosphere. The effect of the radiational changes is also amplified by the present position of the continents, which affects the amount of heat absorbed by the northern and southern hemispheres. The position of the continents also affects the movement of ocean currents, which are a major factor in moving heat from the tropics to the poles, and affects the strength of the monsoon rains in parts of India, Africa, the southwestern United States, and Australia. The current glacial climate depended on slowly falling atmospheric levels of carbon dioxide. Carbon dioxide is absorbed by the oceans and stored as limestone in the shells of sea creatures. Much carbon dioxide was locked up by plants 200 to 300 million years ago in coal and oil. Some carbon dioxide has been absorbed during the last 100 million years by the oxidation of the material exposed by the uplifting of the Himalayas and the Tibetan Plateau. Plants continually transfer carbon to soils, which also store carbon. Bacteria change carbon into methane, which is stored in permafrost under frozen northern bogs; and in clathrates (lattices of methane and water) in cold ocean muds. The recent increase in grasslands may have been related to their more efficient use of carbon dioxide versus most shrubs and trees; grasslands also transfer much carbon to their soils. (One reason grasslands make such good farmland.) Carbon dioxide levels in the atmosphere during past glacial periods have been about 190 parts per million, during interglacials about 280 parts per million. In our industrial world the level is currently over 380 parts per million, and increasing by 1.5 to 2.0 parts per million every year. (The carbon dioxide forcing equivalent of all greenhouse gases is in the mid 400s.) The curve of rising carbon dioxide, measured on Mt. Mauna Loa in Hawaii, is the quintessential signature of modern western civilization.

The difference in atmospheric concentrations of carbon dioxide in different times reflects reallocation of carbon among the oceans, land and atmosphere under different environmental conditions. While the reasons for the reallocation are poorly understood, lower carbon dioxide levels are associated with cooler conditions. A simple explanation for the fall in atmospheric carbon dioxide as the temperature cools is that a cool ocean absorbs more carbon dioxide from the atmosphere than a warm one. Absorption of more carbon dioxide by the oceans then reinforces the atmospheric cooling. This feedback relationship will raise the warming predicted for rising carbon dioxide levels by 50%. (The oceans are a very large sink for carbon dioxide, containing about 50 times that in the atmosphere.) Iron-rich dust falling on iron-poor seas during dry, cold glacial periods may increase the growth of phytoplankton, which die and sink, increasing carbon storage in the oceans and keeping temperatures low. (Iron also increases growth in tropical forests, which also store carbon.) As glaciers melt at the beginning of an interglacial period, carbon is released from newly uncovered northern peat bogs, reinforcing the astronomically-driven warming; as the climate warms further, this process reverses, and carbon’s rate of storage in peat bogs, and also in forests and grasslands increases, pulling carbon dioxide out of the atmosphere and setting the stage for a new glaciation. The 15 millennia of the last interglacial exceed any interglacial of the last 420,000 years in duration, stability, amount of warming, and concentration of greenhouse gases. If orbital geometry were the sole factor in control, our climate should have begun a slow cooling several thousand years ago. Thanks to earth’s feedback mechanisms, carbon dioxide levels were slowly falling until 8000 years ago. The current rapid warming (about 0.75º C. in a century) is thought to be caused largely by the burning of fossil fuels, but clearing forestland for agriculture, growing nitrogen-fixing crops, fertilising crops with artificial nitrogen, raising cattle, and growing irrigated rice also add to rising temperatures. Agricultural activities contribute through the addition to the atmosphere of carbon dioxide, nitrous oxide and methane; like carbon dioxide, nitrous oxide and methane are greenhouse gases. Nitrous oxide is released by bacteria from the breakdown of nitrogen compounds in water or soil (whether from nitrogen-fixing legumes or fertiliser); methane through the bacterial breakdown of carbonaceous material in the guts of cows, and also in rice paddies and water reservoirs. (Swamps, lakes, volcanoes, the guts of termites, and perhaps forests, are natural sources of methane.) Carbon dioxide is released by clearing forests for agriculture (perhaps 20% of current man-made warming gases) and by cultivating soils. (Cultivation speeds up oxidation of the soil’s stores of carbon.) If this interglacial had followed the course of the previous ones, reglaciation should have begun 4000 to 5000 years ago. It is now thought that land clearing for agriculture in Eurasia, which started 8000 years ago, produced enough carbon dioxide to compensate for the declining radiance of the sun, so evened out a natural decline in carbon dioxide, and thus produced our moderate and benign climate. If so, our civilization, which depended on a climate favorable to agriculture, is the result of a lucky accident.

A global warming of more than a few degrees Celsius will make most existing human infrastructure obsolete. Current thinking is that if we can hold carbon dioxide levels, or their equivalent, under 400-450 parts per million, we can keep the warming under 2º C. and escape its worst effects. Since this level is 10 or 15 years away (from 2005), and we are doing essentially nothing to control the gases that cause warming, or to control the growing human population, and changes are taking place in the Arctic and Antarctic with a large potential for positive feedback, escaping the worst seems extremely unlikely. Some infrastructure will be made obsolete by changes in the water cycle. Condensation and rain power the earth’s weather, releasing heat to, and removing it from, the atmosphere. A warmer world is a wetter world, since more water will evaporate from the oceans; and in fact moisture in the upper trophosphere is up 6% since 1982. Warming will affect humidity levels, evapotranspiration from vegetation (a source of moisture for convective rainfall), sea levels, soil moisture levels, rates of storm runoff, of groundwater recharge, snowfall and snowmelt, river flows, lake levels, rates of leaching and erosion in soils. Half the United States’ population lives within 10 miles of the beach. Some writers argue that a temperature rise of 2º C. is too much and that we should try to return to a carbon dioxide level of 350 parts per million. They reason that a rise of 2º C. gives us the temperature of 3 million years ago, when sea level was 20-25 meters (70-80 feet) higher and the coastline of the east coast of the United States south of New York City followed the Orangeburg Scarf, a formation about 60 miles inland of the present coast. (Such a rise would imply more than the meltdown of the Greenland glacier, which is estimated to occur at a rise of about 2.7º C. and would raise sea levels 6 or 7 meters. The meltdown of the Greenland glacier is supposed to take 1000 to 3000 years—or 300 to 1000 years, sources differ—but with glacial meltdowns going on worldwide, and sea levels also rising from thermal expansion, sea level rises of 1 to 4 meters per century are very possible. The earth is currently absorbing enough extra heat to cause sea level rises of a meter per decade if all the heat went to melt ice.)

Changing the amount of water that falls as rain or snow creates other problems. California depends for its summer water supply on thawing snowmelt from the Sierrra Nevada. If more of the snow falls as winter rain and the snow melts a month or two earlier, the available water overall falls. (More flows through the reservoirs. Estimates range up to an 80% decline in available water over the next 50 years.) Mountain glaciers stabilize the summer flows of the great South Asian rivers like the Ganges, and also the flows of many South American rivers, by capturing the variable monsoon rains as snow and providing a strong regular pulse during the summer melting season. Meltwater from Himalayan glaciers provides 60% of the flow of South Asian rivers, whose waters help feed over a billion people. At present rates of melting, such glaciers will be gone in 40 years. Severe storms, those with more than 2 inches of precipitation in 24 hours, have increased 20% over the last 30 years. One-hundred year storms now occur every 9 or 10 years in the Schoharie Valley of New York State. This has required New York City to strengthen Gilboa Dam, one of its water supply dams. Holes were bored down through the dam and rods anchored in the bedrock to hold the dam in place. Water levels had reached 6.5 feet over the dam in 1996; overtopping by 8 feet could cause failure of the dam and flood the valley below. In general, small changes in reservoir inflow can cause large changes in reservoir water yields: that is, too much or too little water. Large inflows increase siltation, which shortens the reservoir’s life. (They also increase its production of methane.) Warmer seas also mean stronger hurricanes (and stronger windstorms in general); whether hurricanes will be more numerous is still debatable. Rising sea levels, and more frequent floods and extremely high tides, driven by more powerful storms, will force the abandonment of much housing along seacoasts and in river floodplains. Saltwater will infiltrate lenses of fresh water near the coast, already depleted by pumping, turning them undrinkable. Losses in the United States will amount to many trillions of dollars. (Florida alone has $3.5 trillion in development at risk from storm surges.)

Warming shifts ecosystem boundaries, usually north (south in the Southern Hemisphere), or upslope. Warming in parts of the American tropics has made the days cloudier and cooler, and the nights warmer, creating favorable conditions for the spread of the chytrid fungus (imported to most of the world on African frogs) among amphibians. In Central America, population after population has been wiped out as the fungus spread up the valleys. In a similar way, tropical diseases will move into temperate regions. The climate will probably become less favorable for agriculture in continental interiors, such as the American Corn Belt, or the Ukrainian Black Earths, where rising temperatures and more sporadic rainfall will reduce yields. Each rise of 1º C. will move the habitat for cultivated grains 100 to 200 kilometers further north, but into subarctic regions where soils are poorer. Rising global temperature will cause the release of more carbon dioxide from subarctic forests and methane from Siberian bogs. In the last decade, the Alaskan tundra has changed from a carbon sink to a carbon source; and much of the boreal spruce forest of northwestern Canada and Alaska has been killed by bark beetles no longer controlled by the length of winter. The carbon dioxide released by the decomposition of the dead trees will add to that in the atmosphere. In parts of Siberia, methane now bubbling up from thawing tundra lakes keeps them from refreezing during the winter. Other lakes are draining away as the permafrost beneath them thaws. One quarter of the land surface of the Northern Hemisphere currently remains frozen year-round. Northern permafrosts contain something like 400 billion tons of methane, a greenhouse gas 20 times more powerful, if shorter-lived, than carbon dioxode, equivalent in warming potential to several centuries of human production of carbon dioxide. Thawing will release it.

* * *

Warm tropical waters flow north with the Gulf Stream and moderate the climate of Europe and eastern North America. Winds pull and push ocean currents. The Gulf Stream is also drawn north by the sinking of cold salty water in the North Atlantic. The tropical waters of the Gulf Stream become denser and more salty from evaporation and cooling as they move north. At 4º C. (39º F.) water reaches its maximum density and the surface water of the Gulf Stream starts to sink through the warmer water below it. The water sinks to the bottom of the ocean and flows south in a return flow towards Antarctica, partly driven by the circumpolar winds about the Southern Ocean. Sinking is helped by the annual freezing of the ocean surface, which takes up fresh water, leaving a pool of cold, salty water behind. Any warming of the ocean’s surface (which reduces the water’s density) or any inflow of fresh water that lessens the water’s saltiness (also lessening its density) slows the sinking of the water. Measurements indicate the sinking of surface water over the underwater ledges between England and Iceland has slowed by 20% since 1970, but the measurements are few. Discharges of the six largest Eurasian rivers into the Arctic Ocean rose about 7% from 1936 to 1999, probably because of increased rainfall. Arctic sea ice has thinned by 40% since the 1980s and its extent has shrunk dramatically. About Antarctica, the extent of sea ice shrank by 25% from the 1950s to the 1970s, a fact that escaped notice in an era without satellites for some time. Ice reflects sunlight, while seawater absorbs it, so melting sea ice produces more warming, and more melting. It now seems the Greenland icecap is also undergoing net melting: another huge potential inflow of fresh water to the North Atlantic. Measurements indicate the salinity of the Arctic Ocean has fallen slightly from 1965 to 1995.

A slowdown in the ocean circulation has various feedback effects. Seas around Europe and north of Iceland would cool. Sea ice would probably increase. Temperatures in Europe would fall, by 5ºF. to 10º F., half of their current advantage over similar latitudes in North America. Wine-growing in much of northern Europe would retreat toward North Africa. Nutrient upwelling, which is driven by currents, would slow throughout the Atlantic Basin. This would lead to a decrease in ocean biomass. Less capture of carbon by plants and slowing of the ocean’s circulation would reduce the carbon storage capacity of the ocean, increasing the atmospheric warming overall. Sea levels would rise about a meter around the North Atlantic Basin from a lessening of the plug-hole effect, caused by the sinking of several billion gallons of water per second. The Indian monsoon would weaken and Central and South America would lose a considerable amount, perhaps half, their rainfall. The global circulation of ocean water is also the main method by which the deep sea is kept oxygenated. A substantial reduction in water exchange between the surface and the depths would result in partial stagnation of the deep sea. This would cause a severe decline in deep ocean biomass, extinction of many marine organisms, and perhaps releases of carbon dioxide and hydrogen sulfide, chemicals toxic to most land organisms. (Hydrogen sulfide, a natural product of decomposition, is released from undersea sediments when oxygen levels fall near zero. Its release turns the water column toxic.) A stalled ocean circulation at the end of the Permian period 251 million years ago wiped out 90-95% of marine life; 70% of land plants and animals also died. The temperature rise was caused by rising levels of carbon dioxide from volcanism. Sea temperatures rose 8º C. at high latitudes, but less in the tropics, reducing the temperature differential between them and thus the circulation. No one has much idea of the time scales involved in such events, but one cycle of deep ocean circulation takes several thousand years (figures range from 1000 to 10,000). The last such ocean-mediated cooling, the Younger Dryas Event, began 12,700 years ago and was probably caused by the draining of remnant glacial lakes (primarily Lake Agassiz) in mid-continent North America down the Saint Lawrence River. The cooling began with a drop in average temperature of 27º F. near Greenland. Winters became several months longer and the atmosphere stormier. The Younger Dryas lasted about 1300 years and ended abruptly, probably within three years. It was associated with drought in Southwest Asia. The drought may have helped push people like the Natufians, who were living in villages near the Jordan Valley and supporting themselves by gathering acorns, pistacios and some wild cereals and by hunting gazelles in a landscape managed by fire, into domesticating cereals and becoming herders of goats and sheep: that is, into becoming agriculturalists. The drought would have reduced the production of acorns and pistacios and made the growing of grain more attractive. During the Younger Dryas Event, tundra returned to northern England. (The pollen of an Arctic flower, Dryas octopetala, is one of its markers.)

It is now thought that the effects of global warming will not be enough to stop the North Atlantic Circulation but will just slow it (estimates are about 25%), and that the warming of the atmosphere will more than compensate for any cooling the slowdown in the circulation causes. Two other man-made climatic effects are more worrisome. One is the release of methane from permafrost in the Arctic and from clathrates (ice lattices) in shallow Arctic seas. Permafrost is already releasing its methane. The last time oceanic clathrates released their methane temperatures jumped 6º-8º C. in a few thousand years. The temperature over the shallow Arctic Ocean shelves must rise only 1º-2º C. for such releases to start.

The other troubling scenario is the collapse of the Amazon rainforest, with the release of the carbon in its vegetation and soils. Trade winds blow Atlantic moisture west over the Amazon Basin. As one heads west, more and more of the water that falls on the forest is transpired from the trees. (Three-quarters of rainfall in the western Amazon is recycled from plants).) Cutting enough of the trees in the eastern parts of the forest (some calculations say 20%) break the cycle, droughts begin to dry the western forest, fires open it up, and the forest collapses through drought and fire into a savanna, emitting the carbon in its trees and soil (500 to 900 tonnes of carbon per hectare) to the atmosphere as carbon dioxide. The forest then collapses from west to east. Of course such releases of carbon dioxide lead to a further warming of the global climate. (Brazil is already the fourth largest emitter of anthropogenic carbon, much of it from forest clearance, and Indonesia’s emissions, largely from clearing and burning its tropical peat swamp forests for palm oil plantations, make its per capita emissions of carbon close to those in the developed world.) Such clearing of tropical forests is completely under human control and could be stopped tomorrow if the parties involved could agree on a scheme for compensation.

In the modern world, surprises abound. Fifty years ago no one suspected that refrigerants released into the atmosphere would cause an increase of ultraviolet radiation at ground level. Depletion of ozone levels in the stratosphere has caused an increase of ultraviolet-B radiation of 10-20% in northern latitudes over the last 30 years and greater increases in the far south (Australia, southern Africa, southern South America). Ultraviolet-B causes skin cancer and cataracts; unfiltered ultraviolet-B would sterilize the surface of the earth and the upper layers of the ocean. (The creation of the ozone shield as a byproduct of the creation of an oxygenated atmosphere by early photosynthesizers allowed the colonization of land by life.) It is now suspected that the warming of the lower atmosphere, the trophosphere, that is, global warming, reinforces the rate of ozone depletion. The lower atmosphere warms by absorbing more of the heat radiating out from the earth, thanks to the presence of elevated amounts of greenhouse gases and water vapor. Since a limited amount of heat is available, increased warming of the lower atmosphere cools the upper atmosphere. Cooling favors the reactions that destroy ozone, which take place at very low temperatures. The upper atmosphere is also contracting (a thermal contraction, one associated with its cooling) at a rate of about a kilometer every six years. This is not a small amount, and no one knows its implications. But such facts abound. The building of very large dams in the Northern Hemisphere over the last 70 years, by concentrating so much weight toward the North Pole, has slowed the rotation of the earth by a fraction of a second a day; so has the warmer atmosphere, which has an increased angular momentum or drag. Modern settlement is associated with drainage (of farm fields, of building sites) and the subsequent lowering of continental water tables has raised ocean levels about three centimeters over the last century (something more than an inch, but another rather large number). Anthropogenic carbon dioxide has made the oceans more acid. (The oceans are the largest reservoir of planetary carbon dioxide, soils are second.) The pH of the ocean was 8.3 after the last ice age; 8.2 before the Industrial Revolution; 8.1 now. As carbon dioxide in the atmosphere becomes more abundant, more of it dissolves in ocean water. Some is removed from the water by living things. A large proportion of the spring and summer blooms of coccolithophoric algae (those with calcium carbonate shells) sink to the bottom of the ocean, thus locking up carbon dioxide from the atmosphere in ocean sediments. But some of the additional carbon dioxide remains in solution and raises the water’s acidity. As the acidity of the ocean rises, carbonate becomes less available, calcium carbonate skeletons harder to form, and less carbon is likely to be stored by living things, even though more of it is available. Life for organisms with carbonate shells, such as oysters and coral reefs, becomes more difficult. Oxygen also becomes harder to extract from seawater as the water becomes more acid; this may affect the growth and reproduction of organisms with high oxygen demands, such as squid, the basis of many oceanic food chains. Toxic metals become more available in a more acid ocean. The ocean is buffered by calcium deposits on its bottom and the circulation of acidic surface water through the deep ocean will eventually reduce its acidity but this takes tens of thousands of years. At the present time humans are releasing carbon dioxide too quickly for the buffering mechanism to work and the surface acidity will continue to rise..

Modern people have other effects on climate. The shading effect of aerosols from the burning of fossil fuels, especially coal; from burning grasslands; from burning dung or wood, reduces heating from the sun at the earth’s surface. Off the east coast of the United States the reduction is about 10%. The aerosols include sulphates, nitrates, sooty organic chemicals and fly ash. Similar reductions are found over the Indian Ocean, from the so-called “brown haze” that hangs over the Indian subcontinent; and over the Yellow Sea, from the cloud that hangs over China. Such aerosols probably reduce global temperature but, settling out over the Arctic, increase the rate of melting of snow (which the Inuit claim now looks yellow). Too small to make good condensation nuclei, they may reduce rainfall. (This seems to be the case in eastern China, where rainfall has fallen from 1965 to 2000, as the countryside industrialized.) They probably change the speed and place of jet stream winds. Despite the phasing out of most chlorofluorocarbons (CFCs) and related chemicals by the Montreal Protocols, ozone depletion lessens very little, probably partly because of anthropogenic cooling of the stratosphere, partly because of cheating, partly because some CFCs are still allowed, partly because of resistance to phasing out some chemicals like the bromine used to sterilize agricultural soils, partly because more chemicals than first suspected are involved. (Much is unforeseen. Fluoroform (HFC-23), a waste product of manufacturing the new refrigerant (HCFC-22), turns out to be an extremely efficient greenhouse gas that is rising in concentration in the atmosphere by 5% a year. Its current volume has the warming potential of 1.6 billion tons of carbon dioxide.) Like the Sumerians, we face a bind: fossil fuel use is causing some of our worst environmental problems, but use of ever cheaper fossil fuels will let us solve the problems global warming is going to cause, such as rebuilding infrastructure, opening up farmland to the north, producing food by bacterial fermentation, and so on. This will lead to a warmer, more unstable climate, and the need for more use of fossil fuels. A major investment in non-carbon energy sources such as solar cells will also cause a spike in the use of fossil fuels (but a temporary one).

The exceptions to the land trip tend to confirm it. Humans now appropriate 30% to 40% of net global terrestrial primary productivity, that is, net annual growth on land, for their own use; this growth is taken through harvested crops, felled timber, grazing by animals, land clearing for agriculture or housing, through forest and grassland fires. Most of the biomass is not used directly. Only a few percent of most crops is used for food; and a small percent of logged trees end up as fiber. We harvest about 35% of the productivity of the oceans. Such use does not slow. In the 1990s the United States converted about 2.2 million acres of open space to developed land, 50% more than in the 1980s. The United States uses about 24% of the biomass its land produces, Western Europe uses 72%, South Asia 80%, South America 6%. (So South America remains wild). As human occupation of the globe increases, empty, more or less wild landscapes rise in value. Such unused, or used and abandoned lands (the drier, rougher American Plains, or cutover but partly regrown forestlands) are seen as a retreat from the real, industrial landscape, and are affordable by those who were more successful in creating that industrial landscape. Empty, wild lands rise in value because they are now scarce.