The Limitations of "Carrying Capacity" Part I

The words "carrying capacity" have the aura of scientific precision and clarity about them. This impression is misleading. Since their first use by French and British colonial administrators in Africa before the Second World War, these words have carried with them a political agenda. As cash crops were introduced into colonial territories, the European rulers wanted to know how much land needed to be left to local residents for their food production. In the 1920s in former French West Africa whole communities had been driven to the point of famine by forced labor with inadequate provision for basic food. "Scientific" management of the colonial enterprise required more accurate determination of basic needs. Anthropologist Audrey Richards studied the cycle of production and consumption of the Bemba people under British colonial rule in the 1930s. Later in Northern Rhodesia (now Zambia) agronomists such as William Allan discovered what came to be called "normal surplus," recognizing that local residents planted enough so that in a year of bad rains they would still meet their needs. This strategy usually produced a "surplus" that the colonial state could tax in a normal or good year. Economist Margaret Haswell documented labor and land utilized in food production in the Gambia, identifying stress points known as "seasonal hunger." These studies were put together in the 1940s and 1950s into a series of simple formulas that allowed colonial planners to estimate the amount of land various groups of subject peoples needed to meet their food needs. Labor and land in excess of these minima could be safely taxed or used for export production.

Oversimplification at the Village Scale

The classic formulas for carrying capacity were very simple. Typically they considered only the number of people to be fed, requirements, average grain yields per unit of land, and the proportion of land that is "rested" each year in order to allow its fertility to recover.

Such an approach to human welfare and ecological sustainability (assuming for a moment that the use of the term carrying capacity today is less cynical than it was fifty years ago) is seriously flawed. The western-trained technocrat thinks of "the environment" as a geometrical container, a box, with "things" in it. Some of these "things" are useful to "man" and are called "resources." The very notion of "carrying capacity"- at the heart of arguments about population growth-is a derivative of such geometrical thinking. Land becomes a geometrical surface which "carries" people: the statistical expression is "persons per square kilometer" or "square mile." These simplified, highly pervasive mental images bear no relation to vernacular thought and action. Far from living out their lives on stages with such linear dimensions, rural people in the Third World create livelihood systems that depend as much on other people as on the flow of energy through natural systems. The shape of their world can change from season to season. There are likely to be both urban and rural lifelines. Mobility across space is common not only among the so-called "nomadic" people of Africa or Central Asia, but also among so-called "sedentary" cultivators and peasants. Many diverse pockets of soil, water, wild and cultivated annual plants, perennial grasses, and trees underpin livelihoods. Human needs for food, water, shelter, fuel, and health care interact with each other strongly and are satisfied within these constantly shifting networks of people and places. Livelihoods are woven together in a series of places as people farm, raise livestock, weave, brew beet, make pots and furniture, produce charcoal and gather forest products. In much of Africa, for example, the poorest "farmers" are not farmers at all, but gain more than half their income from many such "non-farm" activities that are seldom included in calculations of "carrying capacity."

The geometrical abstraction "environment" is more usefully conceptualized as "place." Places have physical characteristics. They also have long, complex human histories. They have stories. They are associated with joy and satisfaction as well as suffering, conflict and pain. The difficulty technocrats have in understanding traditional land tenure and management in the Andes or the great African plateau comes from the emptiness of the abstraction "environment." The human histories of places bond people to them as well as to each other in ways that influence access and land use. The spirit of ancestors dwell in and maintain the fruitfulness of these places. Children learn to honor these ancestors as they learn the details of things that have been done in specific places. For instance, in the flood-retreat irrigation systems of many parts of Africa, dozens of crops are planted as flood waters recede into dry season river banks and as seasonal lakes dry up. Variability in time and space is as central to the livelihood systems of Africa as is the continuity provided by the oral history of people-in-places and myths of creation.

Oversimplification at the Global Scale

The idea of "carrying capacity" misses the richness and creativity of human adaptation to specific places. "Carrying capacity" is too crude a lens through which to view the details of negotiations among people and between people and places. These words also distort our view when applied to the planet as a whole. In the 1980s and 1990s authors have used "carrying capacity" as a metaphor for the pressure of human numbers on planetary systems such as the atmosphere, marine bio-production, and biodiversity. Rough calculations are made by dividing essential resources such as fresh water and arable land by numbers of people in the world or a region of the world.

The deficiencies of this macroscopic use of "carrying capacity" are similar to those we have just criticized at the micro-scale. The complex negotiations among groups of people over access to resources are not part of such analysis. Over the past few hundred years these negotiations have produced a world where middle class citizens of industrial countries consume far more resources than others. A much more accurate expression for this state of affairs is the "ecological footprint," defined as the land area necessary to sustain current levels of resource consumption and waste discharge by a given population.

The ecological footprint for an average North American works out to be between 4-5 hectares when all of the land required to produce food, energy, wood and paper is taken into account, in addition to land degraded by the mining and fabrication of metals, production of petrochemicals and plastics, and land dedicated to the disposal of waste. Just as the "place" discussed earlier is the site of numerous, shifting and interacting processes, the "ecological footprint" allows us to see more clearly the ecological implications of our lifestyle as a whole, not just our consumption of water, or land, or energy.

An additional problem with the notion of "carrying capacity" when used at the global scale is that it gives the impression that this "capacity" is rigidly set and unchangeable. This is far from the truth. As urban gardening explodes around the world, new "capacity" is being created in the rubble of urban civilization. Ecological restoration is also transforming lands laid waste by over-grazing, soil erosion, clear cutting, contamination of waterways, and strip mining.

Just as colonial scientists distilled their limited understanding of "carrying capacity" into simple formulas, current authors have tried to reduce human pressure on the global environment to an expression with the veneer of mathematical precision: I = P x A x T, where "I" is the impact of human pressure, "P" is population numbers, "A" is the level resource consumption, and "T" is the technology used for consumption. One critic, Patricia Hynes, has noted that two critical issues escape this formulation completely. First, as just noted, societies - including even the poorest people - have evolved numerous ways of restoring and conserving nature. She argues that not only is this big "C" missing from the positive side of the "I-PAT" equation, but that much of the modernization that has gone on under the flag "development" since the Second World War has actually undermined the ability of local residents to carry out traditional conservation. Secondly, Hynes argues that impact of military industries and war worldwide make a significant dent in the "capacity" of the earth to sustain life, and that this big "M" for the impact of the military missing from "I-PAT."

One only has to think of the land surrounding the eighteen nuclear weapons processing plants in the U.S. (Savannah River, Rocky Flats, Hanford, etc.) or the large areas of the world where some one hundred million land mines make it impossible to resettle and farm (Afghanistan, Cambodia, Angola, etc.) to appreciate the validity of Hynes' amendments.

The More Difficult but More Fruitful Alternative

The phrase, "carrying capacity," has been so thoroughly misused, that it is useless. It has been distorted first by myopic scientists in the service of colonialism fifty years ago, and more recently by powerful interests in defense of the "American way of life" against the demands by most people for a fair share of the earth's resources. I would urge everyone to take a careful look at the two recent works I have mentioned here, Our Ecological Footprint and Taking Population Out of the Equation. These give a much better handle on the relationship between people and nature. Detailed inquiry is necessary whenever the long-term consequences of human activities are in question. In each community in the world where we may be working, it is possible to identify the rich and the poor, and to understand the livelihood strategies of these groups. It is also possible to trace the regional and global linkages that connect them with powerful corporations and ordinary citizens in other parts of the world. Local conservation and restoration practice and military impact are also easy to document once we look for them. The patterns that emerge are not as simple as the simplistic notion of "carrying capacity," but even though we will have to deal with a more complex picture, at least our vision will not be distorted by oversimplification.

Here is a final illustration to ponder. The coastal mangrove vegetation along the Bay of Bengal is disappearing due to the construction of thousands of salt water ponds for shrimp farming. Asia produced 556,500 tons of cultured shrimp in 1990 - 80% of worldwide production. This occupied 820,000 hectares of coastal land in Asia. Stripped of their protective mangrove forests, these coasts are more vulnerable to the impact of cyclones and erosion. Local farmers are losing rice land to the encroachment of "high value" shrimp ponds owned by absentee landlords. Salt and chemicals used in the ponds, and the shrimps' waste contaminate ground water, making it unfit for irrigation or human drinking. Women complain of having to walk long distances to find the family's water. In the long run the source of shrimp seed may disappear if natural breeding grounds among the roots of the mangroves are completely destroyed.

At first glance this seems to be a good example of decreasing "carrying capacity." Indeed, there is no denying that in the long run land and water resources are being degraded. However in the short run, farmers are able to earn income as laborers on the shrimp farms. Indian transporters and packing factory laborers earn a daily wage. What drives this system? The answer is shrimp consumption in high-income Asian countries (Japan, Taiwan, Singapore, Korea), Europe, and the United States. In this case, then, whose "carrying capacity" is being affected? Shouldn't this situation be thought about in terms of a set of "ecological footprints" rather than simply in terms of local "carrying capacity?" The "ecological footprint" of the family in Boston who cooked up some shrimp cocktail for guests this Christmas extends as far as the Sundarbans in West Bengal. The ecological footprint of Indian investors in Calcutta also reaches out into these coastal communities. Approaching production, consumption, conservation, and restoration in this way is messier than the simple answers produced when we use the idea of "carrying capacity," but in the end we gain insights into the way that our lives are interconnected. We are reminded of the importance of mindful consumption as well as empowerment of local people to choose how they use the land they live on.