The Natural History of the Present, Chapter 5

Chapter 5: Improving the Edible Landscape: Horticulture
At the time of European contact, the most complex civilizations in America north of Mexico were the chiefdoms of the lower Mississippi valley. The Mississipians depended on the cultivation of corn, beans and squash. Corn, or maize, originated as a tropical grass. Corn became a dietary staple in Mexico about 3000 years ago, but Teosinte, the grass from which it came, which has small cobs and small, hard kernels of little nutritional value, was cultivated for 4000 years before that. Teosinte stalks are sweet (modern maize stalks are up to 16% sugar) and Teosinte may have been used to make beer. It took thousands of years for Teosinte to become productive enough to cultivate as a grain. (Anthropologists reason that corn in that part of Mexico was competing with mesquite pods, a gathered crop, as a food, and that grain yields had to reach 200 kilograms per hectare for corn to surpass the calories yielded by mesquite pods and so be worth cultivating. Whether the native tribes made the same utilitarian judgement is another matter. Two hundred kilograms of grain per hectare is what modern peasant farmers in Oaxaca expect and the yield reached 2000-1500BC, when the first evidence of large scale clearing in Oaxaca appears.) Daylength is important to plants and it took more time for corn to make its way north from the tropical Mexican highlands, with days of more or less equal length year-round, to the regions of long summer days in temperate North America. Along with beans and squash, corn became a food crop in eastern North America about 1100 years ago. One can read its spread partly in the increase in river sedimentation in the southeastern United States 1000 years ago, as river lowlands were cleared for crops. The combination of corn, beans and squash is good nutritionally; the proteins in corn and beans compliment each other, and squash seeds are high in protein and fats. It also works horticulturally, with the three crops grown together in the same field. One hectare of corn, beans and squash grown together yields as much food as 1.75 hectares of corn grown alone: the combined crops use water, sunlight and soil nutrients more efficiently.

The corn-growing chiefdoms visited by De Soto in the Southeastern United States in the early 1500s consisted of collections of large villages occupying favorable sites along the Mississippi and its tributaries. The major villages had plazas, ceremonial platforms, and mausoleums. They were connected to other major villages by roads. Satellite villages surrounded the central ones. Large animals like elk and buffalo were scarce. (De Soto never saw a buffalo.) There had been earlier advanced civilisations in the Mississippi Valley. The early mound-building cultures of the Ohio and Illinois valleys had been based partly on North American domesticates, partly on hunting and gathering. Their mounds are now understood as astronomical constructions that mark moonrise at the northernmost point in the moon’s orbit about the earth (a cycle with a period of 18.6 years.) Their crops included a squash grown for its shell and seeds; the oilseeds sunflower and sumpweed; and the small-seeded grains maygrass, little barley, knotweed, and goosefoot. These crops were more difficult to grow and less productive than maize, and the villages of the Mississippians were larger: Cahokia, a city of farmers at the junction of the Misissippi and Missouri rivers had 15,000-30,000 people. As in Amazonia, both cultures used the river overflow lands (the bare ground between the rise and fall of the river) for cultivation. They also cultivated uplands. The Mississippians ditched wet upland prairies and grew rows of corn in the mounded earth. The earlier cultures relied heavily on wild mammals such as deer and squirrels, and also on fish, shellfish, migratory waterfowl, and wild nuts. Forests were probably managed with fire to encourage the growth of nut trees, which are somewhat fire-resistant. Wild nut trees in the Middle West included hickories, chestnuts, oaks and pecans. Two bushels of hickory nuts yield about 28 pounds of edible nutmeat, which would feed a person for a month. Two-thirds of a bushel of white oak acorns yields the same amount of nutmeat (in fewer nuts), but hickory nuts are a more balanced source of amino acids. Nut production is related to crown development, that is, to tree spacing, so forests can be “managed” by fire, which over time produces a park-like forest of large trees. Such management incidently manages them for the squirrels, turkeys, deer, bear, elk and buffalo that compete with people for the nuts. (Besides increasing the yield of nuts, controlled burning, by increasing the yield of browse and herbaceous forage in deciduous forests, can increase the animal biomass by four times.) The yield of white oak acorns in southeastern Ohio is 0 to 156 pounds per acre, of the less edible red oak 5 to 179 pounds per acre, of hickories 5 to 46 pounds per acre. (Total yield of a mixed forest is higher.) The low yields are a defense against seed eaters by the trees. The years of low yields are more or less predictable, and vary from tree to tree or grove to grove. (Red squirrels in the Yukon can predict high cone years in firs, probably through chemical signals in the buds—leaf buds and cone buds differ chemically—and in years that will produce good cone yields the females produce two broods.) The Mississippian chiefdoms collapsed soon after De Soto’s passage, most of them without ever making direct contact with Europeans. Their relatively dense populations made them susceptible to European crowd diseases, which can cause high mortalities in populations without immunity. When La Salle descended the Mississippi River a century after De Soto, he saw few people and many buffalo and elk.

The native population of the Americas before European contact will never be known, but estimates keep going up. A recent one claims 43 to 65 million people for both continents and Central America (or, perhaps, double that), with 3 million people in North America. (Other estimates for North America alone go up to 18 million.) These people were killed less by warfare than by European diseases. The smallpox epidemic of 1520 to 1524, originating in Mexico, is thought to have exposed most of Central and South America, and perhaps parts of North America, to a disease with a mortality rate of 30-70%. (Variola major kills 30% of those who catch it, V. minor 5%.) The people De Soto came near may have been killed by diseases carried by his pigs. Recurring epidemics of smallpox reduced the population of central Mexico 70% in the 30 years following the Spanish conquest, from 25 million to 6 million people. The population finally bottomed out at 700,000 people, a 97% reduction, after 100 years. By 1650 perhaps 5.5 million people were left in the Americas, with 1 million in North America. A hundred years later probably 90% of the native population of North America had been eliminated by successive waves of European diseases. These included smallpox, typhoid, bubonic plague, influenza, mumps, measles and whooping cough in the century after Columbus; typhus, yellow fever, scarlet fever, diptheria, malaria, amebic dysentery, later. Many of the diseases were childhood diseases in Europe, some of which had been affecting Europeans for thousands of years. Despite some immunity (some genetic, some passed on with mother’s milk), children in Europe suffered heavy mortality from them. (Until the 1780s the mortality of European children from childhood diseases was 10-30%.) But when such diseases affect adults who have no immunity to them, the effect on the population is much more severe, since the reproductive population collapses, and children and old people die without those in their vigorous years to support them. The result may have been that by the 1700s and 1800s the Americas were wilder (less managed by people) than for a long time; the forests in 1750 thicker and more extensive than they had been for 1000 years.

At the time of European contact, agriculture was a sideline for many tribes, but the new crops of corn, beans and squash were grown to the limits of their range, and traded further north. (The three were almost always grown together, in the same field, a tradition that may have developed from the observation that wild beans and squash often grow with Teosinte, the ancestor of corn.) That is, their cultivation was regarded as useful, even if they provided less than a third of a group’s calories or, because of poor growing conditions, were not always reliable from year to year. Because most North American tribes depended heavily on gathered and hunted foods, did not have state-like ambitions, did keep large herbivorous animals (goats, pigs, sheep, cattle), whose effects on forest reproduction and maintenance, as well as on wild animal populations, can be large, did not burn lime or brick to build monumental cities, and did not produce large agricultural surpluses, I would call them horticultural rather than agricultural. Their agricultural lands occupied only a tiny percentage of their territories. Eighteen million people in America north of Mexico is about 6% of the current population, 2 million (a current low estimate) less than 1%.

Horticulture, or agriculture, changes the effect of human occupation on the landscape. The adoption of agriculture begins a process that will eventually result in the elimination of the natural edible landscape, and its replacement with a more man-made one. At the northern limits of corn culture the Huron, an Iroquoian tribe, got an estimated 80% of their calories from cultivated crops, 65% of this from corn. (Corn constituted 50-75% of the diet of the southern New England tribes, also serious horticulturalists, in a similar climate.) The Huron lived along a major river drainage east of Lake Huron. Huronia consisted of an upland area of light arable soils surrounded by extensive wetlands, with cedar and alder swamps. The cedar lowlands were winter yarding areas for deer, and the wetlands sources of fish and of game birds, including migratory waterfowl, and of other animals such as muskrat and beaver; the amphibians that lived in them are the basis of several furbearer food chains. Euro-American settlement with its permanent fields, roads and ditches tends to lower water tables, and Huronia now is much drier and less productive of wild beings but more productive of housing and field crops than originally. In addition to crops, 10-15% of the people’s calories is thought to have come from fish, 5% from meat, the rest from gathered wild produce. Calories are not everything and that 15-20% of the Huron’s calories came from protein-rich wild foods is impressive for such a large, more or less settled population. The Huron were healthy, and much larger in stature than the Frenchmen who first contacted them. Since body size is an indication of dietary quality, one can assume their diet was better. (Native Americans were also cleaner. When the six-foot tall Osage of the Missouri River who bathed twice a day met the five-foot four Frenchmen who considered bathing dangerous, the Osage were appalled by the Europeans’ stink.) The Hurons’ population has been estimated at 20,000 before the smallpox epidemics of the 1630s, in a territory of 340 square miles (217,000 acres). About 7000 acres were in crops at any one time. Since fields were used for 10 years, about 3 times this was in long-term fallow. So about 13% of their land was “cultivated,” and 3-4% was under actual cultivation at any given time. Thirty years in fallow was the time the Huron thought necessary to renew the soil, which is similar to estimates in colonial New England or in tobacco and corn growing Virginia. The numbers yield a population density of 60 per square mile for Huronia, but this does not include all the area used for hunting. The fall hunt for deer, for instance, took place in the oakwoods of southern Ontario. It doesn’t include the watersheds of Huronia’s fisheries; or the faraway lands used for breeding and wintering by its migratory waterfowl. However the Huron were surrounded by non-agricultural tribes who also used parts of these territories, and so different peoples fished for the same fish and hunted the same waterfowl, either nearby, or during the animals’ migrations, or on their breeding and wintering grounds.

Where available, fish and shellfish were important supplemental foods for most of the more sedentary tribes. Some Pacific Coast tribes lived almost entirely on marine resources. (Thus they resembled the other peoples of the kelp belt that ran from Japan up the Siberian coast, along the Aleutians and down the North American coast to southern California.) Fish were taken with dip nets, bag nets, seines, weirs, hook and line, and with spears and torches. Freshwater mussels were abundant in aboriginal Middle Western and Southern rivers, many of which were wide and shallow, ideal for shellfish, and marine shellfish were abundant along the coasts. The Huron had settled along a major migratory fish path. They fished the spring spawning runs of walleye, sucker, pike, and sturgeon from March to mid-May, the fall spawning runs of whitefish, lake trout, and cisco in November, and for lake trout, perch and smelt under the ice in winter. The Iroquois confederacy of New York State (a related group) straddled the junction of two great river drainages, the Saint Lawrence and the Mohawk-Hudson, both inhabited by several migratory species of fish. A Jesuit living with the Iroquois in the 1640s reported that a man could spear a thousand eels a night in the waters of Onondaga; this was during the fishes’ fall migrations back to the sea. (One can find such statements about most early American rivers: a protestant missionary in New Jersey in 1680 observed that when the fish were migrating you could catch them with your bare hands in the pool below the Great Falls of the Passaic River, and colonists in Connecticut claimed you could walk across the rivers on the backs of the migrating fish.) A petroglyph of a large shad is pecked into a granite boulder on the headwaters of Meadow Brook, a tributary of the Winnepesaukee River in New Hampshire. Meadow Brook is far from the sea. The Winnepesaukee flows into the Merrimack River, which flows into the Atlantic north of Cape Ann. Shad made their way up to Meadow Creek to spawn. The natives of southern New England had several species of migratory herring, as well as Atlantic salmon, sturgeon and shad and the shellfish of the marine mud flats and river estuaries. A tidal fish weir 4000 years old was found during excavation for a building foundation in what was once Boston harbor (and is now landfill). The weir worked by leading fish coming in on a high tide into a complex of pickets from which it was difficult to escape when the tide fell.

Further west, on the edge of the plains, meat replaced fish as an alternative source of protein for the horticulturalists, though a few tribes netted fish from the prairie rivers. The Hidatsa supplemented the corn, beans and squash they grew along the floodplain of the Missouri with buffalo. They used their large, earth-covered pit houses in late winter, spring and summer. During the summer they grew their crops. The cool weather of fall and early winter were spent in tents on the Plains hunting buffalo. When they left for the hunt, the harvested crops were hidden in pits in the ground from their enemies the Sioux, who knew they would be away hunting buffalo, and would raid their stores. Many of the tribes in the lower Mississippi drainage and the southeastern United States were as agricultural as the Huron.

Generally, agriculturalists modify their landscapes, especially their immediate landscapes, more than hunters and gatherers. Their effects reach further if they have grazing animals, or if populations grow rapidly or develop fuel-using technologies, such as pottery-making and metal smelting. At the time of European contact, agriculture in America north of the Rio Grande seems not to have supported large, organized, hierarchical, warlike states, like those in Mesopotamia, Mexico, or Peru. Some peoples came close, such as the Huron, or the Haudenosaunee Iroquois, the chiefdoms of the lower Mississippi Valley, the Hohokum and Anasazi of the Southwest, but the effects of their environmental manipulations were limited compared with those of other “high” civilizations. Except perhaps in the Southwest, agriculture was not extensive enough and not associated with sufficient population growth or craft use to be environmentally destructive on a large scale. Throughout most of the country, native use of hilled or ridged fields tended to keep soil on the site. In the Southwest, cleared juniper and pinion pine woodlands, once used for several generations to grow corn, might not regenerate. North America had no domesticated grazing animals, whose effect on the landscape can be dramatic. Two candidates, the horse and the camel, died out during the Pleistocene extinctions. Native agriculture had little or no apparent effect on fisheries, and little on sedimentation in estuaries, while Iron Age settlement in Europe had an immediate and lasting effect on both. Studies of river bottoms in the eastern United States indicate large episodes of erosion between 1100 and 1300, along with a disappearance of tree pollen in the sediments, signs that river bottomlands were being cleared to grow maize. The erosion ceased after 1300, though corn continued to be grown. Native Americans modified forests and grasslands by fire, but for the most part so as to maintain plant cover. Populations of some game animals were suppressed, for instance, the buffalo living near the corn cultures of the Mississippi Valley. In California, some marine mammals were hunted to extinction and in the Hudson Estuary and about Chesapeake Bay, the oystershells at the bottoms of 4000 year old shell middens are larger, so one could argue the oysters were (somewhat) over-harvested. (One sees such effects on harvested shellfish worldwide, from the Chesapeake to Denmark.) In areas such as coastal southern New England, population had probably reached its limits, in terms of the land-use strategies the people employed. Most hunting and gathering peoples limit their populations to 60% or less of the maximum an environment can support, perhaps a reasoned calculation of the landscape’s long-term carrying capacity; perhaps a response to the difficulty of harvesting a very high percentage of a landscape’s resources. The land of the New England tribes was nowhere near the state of Europe in 1650, where essentially all the cultivable land was occupied, and the remaining rough uncultivated landscape (the half-fearful wilderness) was subject to grazing and timber cutting, where riverine fisheries were reduced by sedimentation and dams, and wood shortages were common. The Native Americans still relied extensively on gathered and hunted foods and still lived in a whole, integrated landscape. Their burned woodlands, full of game and nut trees (some probably planted), with rivers full of fish, were another sort of cultivated ground: a forest and riverine horticulture. (Southern New Englanders had walnuts, hickory nuts, butternuts, chestnuts and five kinds of edible acorns.)

The effects of agriculture vary. In the American tropics, swidden or slash and burn farming encourages the return of the forest through the clearing and burning of relatively small plots and the planting of multi-layered gardens, including tree crops, which follow the crops of annuals and the beds of cassava. The ash from the burned vegetation provides an initial burst of fertility. The mix of crop plants keeps the ground covered and protected from sun and rain. People may return to a garden plot for 20 years to harvest tree fruits as the forest returns (longer if the trees are palms). Most of the nutrients in tropical forests are in the vegetation, and are rapidly recycled by the forests’ plants and animals; the soils holding up the forest are leached, acidic and poor. Weed pressure usually becomes too much to keep annual crops growing after a few years and yields also fall as nutrients are used up or erode away. Over sufficient time much of the area suitable for cultivation in the landscape may be cleared, more than once, in a very long rotation. Native Americans in the Amazon developed a method of improving tropical soils by adding charcoal, creating so-called black earths or terra prieta soils. (Some modern tribes also do this, making charcoal from plant waste with cool, slow-burning fires.) Charcoal provides a site for nutrients to attach, prevents leaching and encourages the growth of bacteria that increase the soil’s biomass. Black earth soils were enriched with plant wastes, human urine and manure, fish guts and bones, turtle bones, broken pots. Fields of black earth vary in size from 5 to 700 acres, with soil up to 7 feet deep, and remain fertile today. (The beneficial effects of charcoal may last 50,000 years.) While often found on the low bluffs that edge the Amazon floodplain, areas of black earths occur throughout the forest. Tree fruits, swidden gardens, and crops grown in black earths, along with fish, turtles and manatees, fed the large populations along the Amazon described by early explorers. Extensive swidden gardening may have been a recent development, that depended on the introduction of iron axes. Some estimate 12% of the forest cover in the lower Amazon basin has been altered, partly by repeated clearing, partly by the planting of useful trees, especially fruit-bearing palms. Others estimate that 25% of the Amazon basin was farm or agricultural forest at European contact. Peach palms, an apparent domesticate (the fruits vary in size) introduced by Indian farmers to the Carribean and Central America, produce an oily fruit high in proteins and vitamins that yields more calories per acre than rice or maize. The fruit can be dried to make a flour or fermented to make beer. In Central America perhaps 40% of the forest is second growth because of clearing for gardens, and much of the rest more or less modified. The Maya essentially remade a considerable part of the Yucatan lowlands. Much of the jungle there now is second-growth, 1000 years old. Parts of the southern Ontario woodland where the Huron went to hunt deer in the 1600s were wooded with even-aged stands of oak and white pine when the Europeans arrived. These woodlands may have been the result of fire, or they may have been cornfields in the 1400s, but they were likely human artifacts. Any evaluation of the ecological effects of the Eastern or Middle Western agricultural tribes is difficult, because their effects were relatively small, and because so many of them were so badly decimated by European diseases so early. When disease struck, 50-90% of a band might die, leaving a handful of adults. Cultures collapsed, tribes consolidated and their power relations changed. And killing animals for the fur trade distorted the natives’ ecological relations with their landscapes.

Suppose we look at a tribe like the Onondaga of central New York State. It is thought the Onondaga comprised 8-10,000 people (a high estimate) in a territory of approximately 17,500 square kilometers (about 4.25 million acres). This comes to 1 person per 450 acres or about 1.3 people per square mile. An acre of cultivated ground yielded 15 to 20 bushels of shelled corn for an Iroquois cultivator, plus beans and pumpkins. (Other estimates indicate an acre supported from 1 to 5 people.) Farmers growing local strains of corn in Oaxaca, Mexico, today get about 1000 pounds an acre, a comparable amount. A limit is imposed by the amount of land the female members of the family (the farmers) can cultivate. If we take a middle figure of 2 people per cultivated acre (the Huron may have supported 3), the Onondaga had 4-5000 acres of land under cultivation at any one time. This is a negligible percentage of their landscape. Fields were used for 10 years, more or less, and might be used longer if they continued to bear. The Onondaga had been farming the upland areas of their landscape for about 800 years at European contact. When they started to cultivate corn, the people who became the Onondaga moved their villages out of the river valleys of central New York and into the uplands, where the soils were lighter and warmer, and where they built large, palisaded settlements near year-round creeks. Abandoned fields in the northeastern United States return to forest quite quickly (the Huron would have had a forest of four to six inch thick saplings after 30 years), first passing through a berry-and-browse-producing stage, which is useful to both people and game animals. Primary forest returns in 150 to 300 years. Such tracts are identifiable as fields for some time, because of the even age of the trees, and the dominance of so-called pioneer species, but in time windthrow and the movement of more shade-tolerant species into the canopy (beech, hemlock, and sugar maple in the Northeast) will create the more characteristic pattern of early and late successional trees in an old growth forest. Over 800 years, 80 ten-year periods, the Onondaga would have farmed 320-400,000 acres of their upland, that is, something less than 10% of their total homeland, but a much greater percentage of the land they found suitable for farming (perhaps most of it). Slope, aspect, drainage and soil quality were important considerations in locating fields. Villages had to be near water; they also had to be defensible. During 800 years of agriculture some fields were undoubedly cleared more than once, and a considerable percentage of their woodland would have shown the effects of former cultivation.

The effect of a village was not limited to cultivated fields. Firewood was gathered daily. For some years the girdled trees in the fields provided much of it. Shortage of wood was another reason for moving a village. Some New England Indians thought the Pilgrims had come because of a shortage of wood in their country, an idea reinforced when the newcomers began splitting trees into clapboards to ship home. Iroquois villages were palisaded. A village of 2000 people occupied three acres (at a minimum), with a perimeter of 1300 to 1400 feet and so required 1300 to 1400 foot-thick logs, twice that if the palisade was doubled. The tops and branches of these trees would have been another source of firewood. Birches and elms were stripped of their bark to cover longhouses, leaving them standing dead in the forest. Such buildings, which could be 100 or more feet long, took a lot of material. One writer claims that a Huron longhouse needed 450 poles 10 to 30 feet long, 7 to 8 large interior posts, and 4500 square feet of bark covering. A Huron village of 1000 people required 36 such longhouses, on six acres, and 600 acres of cultivated cropland, or about a square mile, for 1000 people. Early writers report Iroquois villages in central New York surrounded by 6 to 8 square miles of cropland. Sometimes the whole cultivated area was enclosed by a palisade: four miles of posts. Birch bark was also used to make canoes and vessels. Like the Onondaga, the Chippewa of the central Great Lakes made maple syrup. A Chippewa woman would store several hundred bark vessels with their spouts in a bark shed in her sugar bush, near the framework of the hut her family would inhabit during sugaring season. Basswood trees were also stripped of bark, the bark soaked in water, the inner part stripped off to make twine. Black ash trees were cut down and pounded with clubs to separate the annual rings; these were cut into strips and used for basketry. A village of 2000 people also produces a considerable amount of faeces and urine (about 10,000 pounds a day), which was apparently distributed haphazardly about the area.

Hunting pressure on small game and some sorts of gathering were greater the nearer one was to the village. Many effects varied with distance. One writer postulates a hierarchical use of fire by horticulturalists like the Iroquois, the Huron and the Cherokee. Fire was used to clear fields near the village; suitable woodland within easy walking distance was burned often (every few years, sometimes every year) to promote the growth of nut trees and berries, and to produce firewood; more distant areas were burned periodically to promote forage for game animals; and even more distant areas were burned occasionally (every 15 to 30 years) in hunts. Fire surrounds for deer were used by the Delaware, the Huron, and also in the southeastern United States, where burning by the Florida natives in their pursuit of game converted the natural oak prairies of Florida to pinewoods, which supported fewer deer. Whether the Onondaga burned their landscape so extensively isn’t certain, but is likely, since burning, by mineralizing the nutrients in soil litter, increases the quantity and quality of forage available to game animals by several times. But except for an occasional burning and periodic gathering and hunting, the great bulk of the landscape of 4.25 million acres was left more or less alone. Lightly burned temperate forests remain forests. The Onondaga’s collecting of bark, building materials and firewood resembled a light selective cut of a small part of the forest, done by hand. The standing dead trees left after their bark was stripped became part of the forest architecture. Indian fields were essentially large gardens. By late July the squash leaves had grown sufficiently dense to protect the soil from erosion. Dead growth was left on the fields over the winter and then burned off in the spring, mineralizing the nutrients in the dead vegetation for use by the new crop. The winter cover helped against erosion, and the use of permanent hills to plant into also tended to keep the soil on the fields. Any soil that eroded off the hills was hoed back into them in the spring. The effect of the hills was to increase the depth of topsoil for the crop plants; they may also have warmed their soil, allowing for earlier planting; whether this was intentional isn’t known. In the upper Midwest flat lakeside soils were turned into ridged fields. The ridges would extend the growing season for up to two months, partly because of cold air drainage off their tops, partly because they warm up more on a sunny day, partly because of the heat storage capacity of the wet earth, or water, in the trenches between them. The Onondaga’s overall effect on the hydrologic cycle, was small, though not quite nothing. Iroquois farmers settled near Crawford Lake, Ontario, in 1268 and built a village near the lakeshore in 1325. The nutrient run-off from their fields, and probably from the village itself, were enough to make the lower levels of the lake anoxic. In 1486 the Iroquois left and the nutrient input dropped, but the water at the Lake bottom remained anoxic for several centuries. Crawford Lake however, is extremely susceptible to small amounts of nutrient disturbance.

The effect of human material lives on the environment runs along a continuum. Aboriginal horticulture and fire modified ecosystems, but they didn’t much affect their nutrient-conserving qualities. Fire had some effect: one of its purposes is to speed up nutrient turnover. The level of use, as well as the cultural practices themselves, were very different from the largely cleared landscape, with its more or less permanent fields, many kept bare over large parts of the year (a good farmer plowed up his cropland in the fall, to be ready for harrowing and seeding in the spring) that European settlement would bring. By 1930, after a hundred years of Euro-American settlement, Onondaga County (the heart of the Onondaga homeland) was 90% deforested; and Onondaga Lake one of the most polluted bodies of water in the country, perhaps in the world; polluted with both industrial waste and sewage. The industrial particulates in the air produced beautiful sunsets. Much of the farmland in Onondaga County couldn’t compete with Middle Western lands, and forest cover amounted to 20% in the 1950s, when I first saw the county. But the influence of Indian settlement was not negligible. One writer speculates that the elimination of 90% of the native peoples of the Americas by European diseases after 1492 allowed sufficient forest regrowth to cause climatic cooling in Europe, that is to say, the cooler centuries of the Little Ice Age. The regrowing forests in the Americas perhaps absorbed enough carbon to bring the atmospheric concentration of carbon dioxide down several parts per million and lower temperatures in northern Europe by 1º- 2º C. in winter, part of a degree in summer.

In most of the United States, fire modified the landscape more than agriculture. The mesic hardwood forests of the eastern United States are susceptible to manipulation by frequent light burning. Low intensity fires volatilize few nutrients and in general increase nutrient mobilization (making them more available to plants) and soil fertility. Fires also increase a landscape’s heterogeneity—its mix of plants and forests in different stages of succession. Europeans found wooded open parkland with oaks, chestnuts, pines and much grass in southern New England, the Chesapeake region and central Mississippi; and thousands of acres of grasslands (so-called barrens) along the Rappahannock River, the Potomac, in the Shenandoah Valley, in western Kentucky, eastern New York, Alabama and Missouri. In the eastern United States grasslands imply frequent burning. Light burning can increase the yield of browse and herbaceous forage in decidous forests by 3 to 7 times, the animal biomass by 4 times. At the time of European contact, the tribes in southern New England were burning their woods in spring and fall on regular rotations. Burning tended to favor oaks and chestnuts, useful for their nuts, which were also eaten by game animals, and created an open grassy landscape of large nut-bearing trees, with pines and whatever other species could tolerate the fires or sprout from stumps. Burning regenerated browse (for game) and berry plants (for game and people). It expanded areas of shrubland (created naturally by river flooding, beaver meadows, windstorms and wildfires), habitat for birds like the yellow-breasted chat, brown thrasher, indigo bunting, chestnut-sided and mourning warblers, birds which were less common in less manipulated natural forests. (Audubon saw a chestnut-sided warbler, a common species of the forest edge today, once.) Only parts of any landscape were suitable for burning. Beech and maple forests tended to be too wet. The conifer forests of the higher elevations or more northern latitudes of New England and Canada were also too wet, and when they burned, burned catastrophically, setting regeneration back to zero. (The Cree occasionally burned them, sometimes by mistake. When not too wet, the boreal forest might be intentionally burned. It was burned along trails and traplines to help access or improve the habitat; areas of dead trees or blowdown might be burned to clear away the trees; blueberry barrens were burned every two or three years to improve the crop.) The extensive cedar swamps of New England were deer yarding areas.

Pollen studies of pond sediments indicate that forests in the Cumberland Mountains of Tennessee began to be burned over about 3000 years ago, some time after people in that area had begun domesticating native plants. In the Cumberlands burning both altered and partly cleared the forest, changing a forest of cedar, hemlock and mixed hardwoods to one of oaks, chestnuts, pines, and sugar maples, with many sunny openings. In the same period, 200 miles southeast of the Cumberlands, people were firing the upper slopes of the Blue Ridge mountains in spring and fall to create a similar forest of widely spaced chestnuts, oaks, and hickories, whose nuts and acorns were useful as food and also attracted elk, deer, bear, turkeys, perhaps buffalo (which crossed the Mississippi heading east about a thousand years ago). Such manipulation altered the tree composition of the forest and changed its nutrient cycles. Some nitrogen and carbon would have been volatilized, and the nutrient cycles speeded up. A frequently burned landscape was a mosaic of young and old trees, with small clearings. The burning that produced such landscapes was periodic and light.

Populations of birds, amphibians, and soil organisms in the burned-over areas changed, some reduced, some made more abundant. Much of the landscape was left unaltered and so able to take up what nutrients were released. Human settlement was concentrated in the alluvial valleys of large rivers and on lakeshores with their good soils (and thus more abundant game) and fish and shellfish. While such regions were managed relatively intensively for hunted and collected foods, and for horticulture (though much less intensively than the Europeans, whose landscapes would support 10 to 100 times more people), much of the landscape was little used. In frequently burned landscapes old trees predominated, with their large crops of nuts. If Native American cropland supported 2 people per acre, then a population of 5 to 10 million people in what is now the eastern United States had 2.5-5 million acres of cropland at any one time, plus as much as 150-200 million acres of young successional and maturing second growth forest. These figures are probably over-estimates, since many tribes in the Mississippi drainage farmed river bottoms, where their lands were renewed by floods, and so used the same fields for long periods of time (there was no need to rotate them into forest). Cropland in the eastern United States today amounts to 278 million acres, all of it in use at once; commercially cut forestland, where old trees are rare, constitutes much of the forest (that is, much of the remaining landscape that is not developed for settlement).

The California tribes may have modified their landscape the most. In the better-watered coastal ranges, 1000 people might inhabit a village of wooden-sided pit houses. Villages were inhabited for centuries. As among the natives of the Northwest coast, there was some division of the population into elites, ritual specialists, craftspeople and ordinary people. California remained the great exception in the Americas, in that the people grew no crops in a climate in which they could have. Californians lived on acorns and marine resources. The combination had the advantage that droughts, which would reduce the acorn crop, were usually associated with upwellings of deep water along the coast, which increased the supply of fish and shellfish. California has a Mediterranean climate of winter rains and summer drought and so is more suitable for the winter grains of the Old World than for the summer crops of corn and beans of the New World. The Californians could have grown corn on the flood plains of receding rivers, as the Mohave did along the banks of the lower Colorado, or practised irrigation like the Pima of Arizona, or ditched wetlands like the corn-growing Middle Westerners. They certainly would have been aware of such practices. The Europeans began to cultivate the margins of seasonal lakes that were formed by spring snowmelt from the Sierras, as soon as they realized the possibilities. One example was the lake created by the Kern River, near present-day Bakersfield, California. Soon the new people dammed the Kern, making the whole of the lake bottom cultivable, and spreading out the irrigation water over the summer. When all the land and water was used for agriculture, a wonderland for waterfowl was eliminated. (In modern times, irrigated lands created by similar projects in Africa have generally been much less productive than the wetlands destroyed by the dams, where farmers planted rice on the banks of receding rivers and lakes, herders used the new grass, fishermen caught the fish that bred in the former wetland.) Perhaps the Californians didn’t see the need for additional supplies of carbohydrates; they had several species of oaks with edible acorns scattered over the uplands and in the gallery forests along the rivers that crossed the Central Valley. They may have domesticated a walnut, a thin-shelled form of which grows about former villages. In the high deserts, pinion pines were managed for their nuts. In the Mohave Desert mesquite trees were pruned and cleared, and desert fan palms, which produce an edible fruit, maintained by burning and clearing. The palms themselves may have been dispersed by people. California was relatively crowded, with well over a hundred tribes. It may have held 10% of the Native American population north of Mexico. Population densities along the north coast, with plentiful rainfall and a varied habitat, reached 6 people per square mile. The landscape included grassland that supported deer and elk (and antelope in the Central Valley), chapparral (more deer pasture), rivers with salmon and other fish and crayfish, and several species of oaks with edible acorns. Acorn yields went as high as 700 pounds per acre. Such yields, if fully exploited, would have supported 50 times more people than were in the area when the Europeans arrived. Acorns are laborious to process; the shelling, pounding, leaching and boiling required to process five pounds of acorn meal (enough for several days) would take a California woman seven hours. In some tribes the right to harvest certain trees or groves was inherited. Oaks would continue to bear for centuries.

Six people per square mile is high for a gathering people. The Cree landscape supported one person per 75 square miles (0.013 people per square mile); the Onondaga 1.3 people per square mile (for the whole occupied area). The woods of Maine were supposed to have supported 0.4 people per square mile, the corn growing land of southern New England almost 3 people per square mile. Twentieth century Americans considered one person per square mile the density of the frontier. An early version of the Homestead Act allotted 160 acres, 0.25 square mile, to a family. For a family of 5, that comes to 20 people per square mile; but for a market, not a subsistence, economy. In aboriginal California (not a market economy) perhaps the oaks, deer, wild grass seeds, marine mammals, salmon, and other fish and shellfish made crops unnecessary, from the point of view of the native population.

Fire was the major tool of landscape management in California. Light annual fires kept Douglas fir from invading the oak savannahs and increased the productivity of the native bunch grasses, whose seeds were harvested for food and which were grazed in winter by antelope, elk and deer. The Yurok and Karok burned to increase the productivity of huckleberries, hazelnuts (for nuts; and the stems for basketry), bear grass (a lily), grass seeds, acorns, and wild tobacco. The Chumash burned grasslands after the seed harvest to promote new seed growth and to hunt rabbits. In the Willamette Valley of western Oregon burning encouraged the growth of camas, bracken and nettles (all food plants) and the grassland (the animal pasture) in which they grew. By speeding up the turnover of nutrients, burning increased the yield of oaks. Grasslands and chapparral were usually burned in the fall. Chapparral would be burned only once every several years. Firing chapparral increases the number of deer it can support by a factor of 3 to 4, from about 30 per square mile in unburned scrub to 98 in the first year following burning, to 131 in the second year, after which the numbers slowly fall. Fire drives were also used in hunting. An estimated 1.5 million antelope inhabited the Central Valley and its wetlands were a winter home for 60 million waterfowl. (In the early 1900s householders in the Los Angeles Basin still shot passing waterfowl from their porches.) Bunch grasses could also be burned in late winter or spring to lure grazing animals, such as antelope. Bunch grasses do not survive continuous grazing pressure (deer, elk and antelope are browsers as well as grazers) and cattle grazing has eliminated much of the native grassland of California. Salmon, along with shellfish and marine mammals, were also a basis of the California diet. If the rivers allowed, salmon were caught with weirs. A good weir will catch a great many of the fish. So one could say the fishery was managed. Different tribes generally inhabited different reaches of a river, and the tribe downstream could have taken most of the fish. But, probably under threat of retaliation, they left fish for the upstream people; and everyone left fish to spawn. Some writers claim the Californians reduced the populations of deer, elk, some shellfish and sturgeon. They killed mostly female and young seals and sea lions and over time eliminated the nurseries of these animals on the mainland. They hunted the kelp-grazing sea cows to extinction.

Would such landscapes have appeared pristine to our eyes? In many cases their vegetation was altered by burning. Since the fires were periodic and light, much of this might only have been apparent to an acute observer. Audubon however remarked on the intense smokiness of the autumn air in the Mississippi valley in the 1820s; and John Wesley Powell mentioned that in a summer spent among the foothills of the Rockies in the 1880s, months entirely among the mountains, he never saw a mountain peak because of the smoke in the air. Fires naturally burned millions of acres annually in the dry grasslands and forests of the West and more fires were set by the native inhabitants. It is now thought that the open stands of longleaf pine once characteristic of the southeastern United States were a fire subclimax of the eastern deciduous woodlands. Fire triggers a growth spurt in longleaf pine seedlings but kills most young deciduous trees. Modern longleaf forests that are no longer burned are invaded by oak-hickory forest. To keep oak from dominating, the woods must be burned every 2 to 5 years in the spring; both the time of the burn and its frequency are important. So these forests, which covered millions of acres (and are almost all gone, replaced by fields of corn and soybeans), were probably human artifacts. In the Northeast a more subtle effect on forests may have been caused by heavy hunting of white-tailed deer. Browsing by deer differentially effects the survival of tree seedlings, and so the future trees of the forest. Thus reducing the density of deer changes the composition of the future forest. Similar effects would have occurred wherever large herbivores were reduced in numbers. Such reductions are not necessarily negative and were not universal. It has been proposed that the no-man’s lands between tribal territories functioned as sanctuaries where game animals increased in number and from where they repopulated the areas in which they were hunted more heavily.

Near villages, forests would have shown the effects of the gathering of firewood, bark and building materials. The Nootka, one of the salmon tribes of the Pacific Northwest, built timber-framed houses sided with red cedar planks. The planks were split from living trees. A set of house planks represented considerable effort on the part of the owner and were carried between summer and winter dwellings by canoe. (Several trips must have been required.) Old-growth red cedar are large trees, 6 to 8 feet in diameter above the root buttress. To get a plank from one, a man cut a groove at the bottom of the tree deep enough to form the bottom of the plank, and then another groove at the top, 20 to 60 feet up the trunk, depending on the length required. A split was opened at the top cut and a long pole worked into it, and the pole left in place for the movement of the tree in the wind to split off the plank. Once free, the plank would be cut loose and squared up with an adze. (Nineteenth century travellers remarked on the “nibbles” made by native adze-heads of copper, stone, or bone.) A house required many planks and a village had tens of houses. So a walker in the woods in Nootka country would have come across stands of strangely deformed cedars, many of which would probably stand for centuries after such mutilation. Of course, since the trees stood, and if alive produced seeds, and if dead still constituted part of the architecture and nutritional status of the forest, such “mutilation” was much less harmful to the woods than modern logging. Such use would only have affected accessible stands of trees, and only some of those.

At the time of European contact, while human use would have affected the appearance and biological structure of much of the North American landscape, human effect on the overall ecological functioning of that landscape was still small. As a collection of nutrient-recycling ecosystems, the landscape still worked well. One can see this in its abundant fisheries, songbirds, and game animals, all of whose populations collapsed after European settlement, as the landscapes were altered and the native beings replaced by crops and by domestic and introduced animals. This is why the extinction of the Pleistocene big game, which unquestionably coincided with the spread of people, and which was probably largely caused by them, seems such an anomaly. Perhaps big targets are tempting; and perhaps the climatic changes of the Pleistocene were more abrupt and severe in North America, whose shape (a north-south plain between mountain ranges) tends to amplify swings in temperature. Extinctions caused by people are common on islands. The Maori, and the egg-eating Pacific rats they brought with them, killed off the large flightless birds of New Zealand within a few hundred years of settlement. The unwary birds were easy to kill and the rats increased in numbers quickly. With the moas went the world’s largest eagle, Haast’s eagle, which weighed 30 pounds, had a wingspan of 9 feet (short for its weight), and approached the size limits for powered flight. The eagle depended on the large moas, which were 15 times its size, for prey. It killed them by striking them in the head.