Sustainability?

Sustainability ?

The idea of the balance of nature and of people’s sustainable use of nature are human notions that come from looking at nature from relatively short periods of time. They likely have limited application in the natural world.

After the last glaciation, the temperate world reassembled itself from seeds that arrived on foot, in poop, in beaks, in the stomachs of fish, or on the wind. Plants moved north, their seeds carried by birds, squirrels, ants, high winds, floods, accompanied by animals that ate them. People were part of these assembling landscapes. In Europe the closest relatives of Homo sapiens , the Neanderthal people, went extinct about 30,000 years ago, leaving modern people, with their spears and firesticks, along with mammoths, as the major influence on the biotic environment. The continental glaciers began to retreat about 20,000 years ago, and sea level rose (eventually by 360 feet), forcing people and animals inland, off the continental shelves. The climate moderated (and dried further south), forests moved north, and the hairy elephants found their habitat growing smaller, their predators more aggressive, life more difficult.

The primeval forests of temperate Europe and North America are about six thousand years old. Probably from the beginning, people burned them. Perhaps people were used to savannah and steppe. Australians burned to ‘clean’ the land and make travel easier, thus converting brushlands to grass and eliminating the food of many native animals. Burning northeastern American forests thinned the trees and pruned and invigorated the understory, which regrew, and whose new leaves, stems and berries fed many birds and animals, increasing by several times the abundance of game animals (grouse, rabbits, deer). Burning created forests of large old nut-bearing trees. Some North American landscapes—the grassy meadows with elk and buffalo in the forests of Kentucky, the scrub oak and berry barrens of New England, home of the heath hen, which disappeared as its landscape was converted to closed forest or farm—may have been burned continuously for several thousand years: people had inhabited these places before the forest was there. Oysters became abundant in northeastern estuaries about 4000 years ago, as the rise in the sea level slowed, and soon after became a major part of the native diet. Abundant fish and shellfish made coastal lands desirable and Native Americans ate a lot of both: the largest oyster shells and fish skeletons are found at the bottom of Indian middens. Fire could make some environments less ‘sustainable.’ The extensive longleaf pine forests of the coastal Southeast were maintained by human burning and without fire succeed to mixed oak and hickory forest—an environment more productive of game animals. Similarly the slash pine forests of Florida were produced by Indians using fire to drive deer, which became less abundant in those forests than in the mixed scrub that preceded them. (All the same, deer were phenomenally abundant in the aboriginal Southeast.) Red spruce, the signature tree of the uplands of New York State and New England for the nineteenth century loggers, became abundant in that northern hardwood forest relatively recently, just in time for their slow-growing trunks to produce the 2-3 foot thick logs whose sawn joists now hold up the floors of New York City apartments. Abundance in the forests and oceans was produced by chance, competition and time—that is, by the long history of these environments—and by the restriction of human tools for the most part to stone axes, digging sticks, bows and arrows, bone needles, fire. As more extensive agriculture began to replace foraging and horticulture, as animals were domesticated, and the use of iron and burned brick replaced renewable materials, people got shorter, less healthy and more abundant, and the balance between the civilized world and the natural worlds shifted.

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The idea of ‘the balance of nature’ comes from the typical J-shaped curve of population growth: populations of animals tend to level off after a period of exponential growth. Animal populations are limited by weather (in itself or through its effects on food plants), competition, parasites and predators. The effects of food supply, parasites, and microbial predators are often density dependent. The parasite that limits red grouse populations in Scotland is weather dependent and so the grouse population fluctuates irregularly. Red grouse would have more large predators (peregrine falcons, owls, foxes), which might or might not affect their populations, if they weren’t eliminated by gamekeepers. Icelandic ptarmigan are hunted by gyrfalcons and snowshoe hares in the Canadian arctic by lynx. Both prey animals follow regular 7-10 year cycles of increase and decline, that of the hare followed, at a remove, by the lynx. The large predators don’t cause the cycles, which are thought to be density dependent. Density dependent cycles are often controlled by the abundance of food plants (that is, by competition: thought to be the case in the hare) or by parasites, microbial or multicellular, probably the case with the ptarmigan.

Wolves in Yellowstone Park seem to keep elk populations about 30% below what plants and the weather would allow, with benefits to the landscape (the recovery of aspen groves along streams, the return of beaver and many songbirds, aggradation of stream beds, healthier populations of trout). Declining elk populations can however be eliminated by wolves, as mountain lions are eliminating remnant populations of bighorn sheep in the California Sierra (keeping the terrified sheep above snowline in winter), or wolves reduce small populations of moose in Alaska. Insect populations often go through rapid increases, controlled only by a disease (as in gypsy moth caterpillars), a change in the weather, or the elimination of the food supply (as in spruce budworm outbreaks in mature balsam fir forests in Atlantic Canada, which end with the burning of the forest). Outbreaks are probably the result of weather conditions, along with abundant food. (The explosion of pine bark beetles that is killing million of acres of tree in the western United States, Canada and Alaska is probably caused by the significantly warmer winters and longer summers that allow populations of the insects to build up, as well as by a century of poor forest management that has left a population of vulnerable trees.) Insect populations may increase more than a million times over ‘normal’ and overwhelm their predators (wood warblers foraging on spruce budworm in Canada, for instance). With gypsy moth caterpillars, a virus eventually infects the expanding population and kills most of the insects. In between outbreaks, predation by white footed mice on gypsy moth egg cases is thought to control the population. Red tides in the ocean (populations of single celled dinoflagellates toxic to vertebrates that color the water red) occur where weather and nutrient supply are favorable (warm, nitrogen-rich seas: for instance, off the west coast of Florida). Red tides disappear when the nutrients are gone (though they produce more in tons of rotting fish), or when weather or currents disrupt them (a matter of ‘chance’).

The ‘balance of nature’ is an ideal formulation of a messy, chaotic natural world. ‘Control’ in nature is not the same as ‘control’ on a factory assembly line. The natural world changes, partly because of weather, partly because of its own internal dynamics and the trajectory its history has put it on, partly from the influence of solar irradiance and plate tectonics, and human influence on this world is only partly predictable.


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‘Sustainability’ competes with capitalist economics. The abundance of animals and trees in North America bewitched the Europeans but they lost no time into converting the landscape into something more marketable (logs, fish oil, salted meat, farms). No timber company or landowner is going to wait 300 years to harvest a mature red spruce or white pine, 150-300 to harvest mature red oak or sugar maple, 500 years for an eastern hemlock, 700 years for a coastal Douglas fir or redwood. No capitalist society is going to let enough of the natural landscape remain in forest, grassland or swamp (a reasonable number is 40-60%) to let that landscape function in a real way, with herbivores, predators, insects, amphibians, change, chance, fish, though over the long term such management may be more profitable. (Over that long a term we are all dead.) Sustainability in a coppiced medieval woodland meant the trees that sprouted from stumps could be cut every ten or fifteen years for fuel (the ‘sustained yield’) with some trees allowed to mature further for building timbers. Such forests are very different from native ones (for one thing, they produce very little timber and mast) but provide some habitat for birds, for deer and boar, mice, voles, frogs, mushrooms. The tree roots hold the soil and minimize erosion and (perhaps) loss of nutrients after a cutting cycle.

Formerly sustainable agricultural landscapes often depended on the health of the surrounding forest. Paddy rice in the Philippines and Indonesia depended on manure from water buffalo, which were fed on forage harvested from the forest. Tropical soils are in general poor. The fertility of the rice paddy came partly from the forest (through water and manure), partly from nitrogen fixing Azolla plants growing in the paddy’s water, partly from insects and plankton recycled through the fish that colonized the paddy. The mineral content and seasonal availability of the water that fed the paddy depended on the health of the whole forested watershed, which also produced fuel, nuts and fruits, medicines and building material. Logging the forest destroyed the water source and removed the forest’s other fruits. So the paddy was sustainable within limits. Too many people, or too much demand put on the forest for other income, destroyed the system.

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Like large old trees, Atlantic salmon were once abundant in northeastern rivers. (Shad and river herring were more so and their ranges extended south, into the Middle Atlantic states.) When the Europeans arrived in the 1600s Atlantic salmon had been fished for several thousand years by settled populations of Native Americans, though ones in which salmon outnumbered people by 1000 to 1. For the last several hundred of those years many of the natives were farming peoples (horticulturalists). The European settlers of the 1600s and 1700s were also farmers, but they grew crops for market as well as for subsistence, and changes in the rivers caused by their more extensive and intensive use of the landscape reduced the landscape’s suitability for fish. Fishing for subsistence and to sell reduced the numbers of fish. Dams cut off rivers to fish migration, siltation shallowed them and covered spawning gravels with mud, cutting trees along their banks let the water warm in summer. Without the forest, summer water levels were lower and without trees to fall into them, rivers lost their deep pools. High rates of fall and winter runoff from cleared ground scoured out fish nests. The logs in spring log drives killed fish directly. The economic outlook of the Europeans, the pattern of European settlement, the density of settlers, made their settlement (as far as the rivers were concerned) ‘unsustainable.’

Much the same thing has happened in the oceans. Postwar fishery biologists mistook the ability of fish populations to recover from fishing. It was thought that catching a large percent of the population yearly would, by reducing competition, let the young fish grow faster and produce a larger number of fish indefinitely. But taking most of the large fish has an evolutionary effect on a population of fish. The fish that breed at earlier ages, when they are smaller, produce more young, and begin to dominate the population. But smaller female fish produce fewer and less viable eggs, so the population becomes less able to reproduce itself. Weather also strongly affects the survival of juvenile fish. A population of poor breeders reduced by bad weather finds it harder to recover. Predation on fish eggs and larvae by other fish and invertebrates have a larger effect. Trawling for fish also destroyed the bottom habitat, turning the coral and invertebrate forests of the seafloor into muddy plains. Development and nutrient runoff reduced the quality of breeding and nursery habitat in the estuaries where most marine species breed and grow to maturity. The forage fish on which large predatory fish feed were fished for food for farmed fish and for chicken and pigs. So over time, settlement and fishing pressure also made the marine fishery ‘unsustainable’. The continuing development of fish farming and the exploitation of new stocks of wild fish means fish will be available until (like oil) one day they aren’t.

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Energy flows through living things, letting them grow and maintain themselves, and ends up lost to space as heat. Without a continuous source of energy the unlikely combination of matter that is life on earth would not be possible.

The sun powers life on the surface of the earth, though a not inconsiderable biosphere deep below the surface (warmed by the radioactive decay of the earth’s interior) is powered by the energy in chemical compounds. Biological life is ‘sustainable’ in that the sun will keep shining for another 500 million years. Life also depends on large, chemically unstable, biogeochemical pools of minerals like carbon, nitrogen and phosphorus. These biogeochemical pools are maintained (more or less) by living things. For instance, carbon enters the atmosphere from chemical reactions deep in the earth through the vents of volcanoes. It is incorporated into living tissue of plants through photosynthesis, into animals and fungi when they ‘eat’ (break down) plants, and into predatory animals when they ‘eat’ the plant eaters. Carbon from plants that was stored as coal, oil and natural gas also enters the atmosphere through fires, from warming bottom muds of oceans or thawing tundra, from the subduction of continental plates (and then once again through deep ocean vents or volcanoes). Nitrogen is a major constituent of the atmosphere and is put in a usable form by lightning and nitrogen fixing bacteria, some of which are allied with the roots of higher plants. That caught in the biological pool is recycled many times before escaping back to the inert form of the atmospheric gas. Phosphorus is cycled between land and sea. Sulfur, iron and potassium have their own cycles. The minerals necessary for life are ‘sustainable’ in that the pools are large. But there are limits. The growth of land plants is often limited by the supply of nitrogen, of riverine plankton by phosphorus. Iron is a limiting nutrient in the oceans and in tropical forests. Sulfur can be a limiting nutrient in tropical soils. All nutrients become limited at the sea surface and are renewed by upwelling from below, which explains why some areas of the sea, where nutrient rich cold currents meet warmer waters, are so productive. Before human intervention in the nutrient pools, nutrient-limited habitats (coral reefs, most forests) had developed recycling techniques that (where climate permitted) allowed for a great abundance of living things (many species of plants and animals) and a large standing biomass (of trees, prairie grasses, buffalo). But this abundance of wildlife or trees was often easily eliminated by over exploitation and might then take a great time to re-establish itself (if it would do so, the ecosystem having been put on a new trajectory by human intervention). At present, thanks to the combustion of fossil fuels and the use of fertilizers, people have doubled the amount of available nitrogen and greatly increased that of phosphorus. The more available nutrients tend to simplify former habitats, turning, for instance, perennial grasslands into annual ones, and favoring early seral species over trees of the primary forest.

With the help of limitless energy from fossil fuels over the last century and a half, we have also introduced many new minerals into the pools of biologically active compounds. Chlorine is usefully reactive. The modern chemical industry is largely based on the chemistry of chlorine and so many of the new compounds are chlorinated hydrocarbons, such as DDT. DDT slowly breaks down (sunlight, bacterial action) into more toxic daughters. Along with other chlorinated hydrocarbons, it is raised by storms from the bottoms of lakes and seas, into which it has been washed or dumped, or onto which it has settled from the air. Once in the water column, chlorinated hydrocarbons are adsorbed on the fatty surfaces of living material and taken up by plankton, cycled through zooplankton, small fish, larger fish, sea birds, sea mammals, all the time becoming more concentrated in fat, and also drifting down towards the sea bottom, in fish poop or the fat in dead seals and whales, from which storms will raise them once again. Many chlorinated hydrocarbons are hormone mimics and disrupt embryonic development in vertebrates (especially those that spend much time exposed to them in water), lower the functioning of immune systems and (probably partly through those two mechanisms) are implicated in many types of cancer, in many animals and humans. The brominated hydrocarbons are similar. Such compounds, new to the microbial world, are only slowly broken down (that is, torn apart for the energy in their chemical bonds) by microorganisms.

We have also greatly increased the biogeochemical pools of heavy metals, such as lead, cadmium and mercury, some of which have known and deleterious effects on living things. Lead concentrations in the modern atmosphere are several thousand times that of the Paleolithic background. Lead and mercury are neurotoxins. The atmospheric concentration of mercury continues to rise, like carbon dioxide, by about 2% per year.

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Against this background, a sustainable society is one in which we stay out of the way. Sustainability implies sufficient ‘natural landscapes’ (Eugene Odum said 40% of any landscape) to let the natural world work and adapt to longterm changes. In many landscapes (the urban and suburban landscapes around large lowland cities) this is no longer possible but might be more so one day as rising seas and higher rivers make abandoning many settled lands necessary. Such ‘wild’ landscapes should be connected and (ideally) would blend into suburban lands with sufficient native plant cover to support some wildlife (especially insect and amphibian life). Wild landscapes should include all ecosystems and subecosystems but be concentrated where they do the most good: along streams and rivers to allow floods to spread out (floodplains provide essential habitat for many species of fish), and to soak up silt, pollutants and nutrients running off developed land; on aquifer recharge areas (ditto); along migratory pathways and in nesting and wintering areas of birds, mammals and invertebrates; along coasts, to allow for storm surges and the alongshore movement of sand. If the massive movement of human populations climate change will cause turns out to be orderly, much of our pattern of settlement could be revised: cities and roads could be located above (rather than on) river floodplains, coastal cities live surrounded by their natural wetlands. Old growth would climb up the banks of salmon streams.

Sustainable agriculture would focus on the agricultural landscape as well as on crop production. Meadows and woods amidst cropland would catch nutrients and silt running off the fields (already reduced by crop rotation, strip cropping and less use of manufactured fertiliser). Such lands would also recharge water tables and streams; provide habitat for populations of native pollinators and bats; for predatory and parasitic insects that help control crop eating insects; for insects that feed on weeds (such as the larvae of the American painted lady butterfly on Canada thistle). Wild lands would also provide habitat for mammals and birds (foxes, owls, falcons) that prey on mammals and insects that damage crops. Some of the herbivores of these wild lands (say, the corn and alfalfa eating white tailed deer in Wisconsin dairy country) would have to be controlled by people, since it is doubtful that people will willingly coexist with mountain lions and wolves (as Italians—for the most part unknowingly—do with Eurasian wolves in Tuscany). Forestlands would be managed for their animals, nuts, mushrooms and fish as well as their timber. Some landscapes, like the short grass plains, might be managed communally as semi-natural pasture for their native grazers (the idea of the ‘buffalo commons’). In this case a corporation of landowners replaces the organization of the medieval village or the tribe; and mule deer, elk, bighorn sheep, coyotes, wolves, prairie dogs, and grizzlies share the grasslands with the buffalo.

Riverine fisheries and marine estuaries would be major beneficiaries of such a resettlement of the landscape.

The industrial world would abandon the chemistry of chlorine for less toxic alternatives. (Carpets made by the Steelcase Corporation are compostable and recyclable. No toxic materials are used in the manufacturing process.) Chip factories would degrease with ethyl lactate, carbon dioxide or steam. Demolished buildings would be taken apart so their materials could be reused. Dumps would be mined. The wastes of one industry would become the raw materials of another. Water use by power plants and paper mills would be cut by 90% or more (doable now) making it possible to locate paper mills in cities, where waste paper is a major resource (and cleaned sewer water another), and reducing the effects of both on rivers (power plants are the greatest industrial users of water). Energy use will fall as buildings are better insulated, cooled and lighted. More electricity will come from the sun or geothermal heat, house heat or coolness from the ground. Our impact on the global cycles of water, carbon, nitrogen and phosphorus will lessen. The human population will slowly fall as women become better educated and able to control their destinies.