Carrying Capacity

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Different species with different resource requirements impose loads of different magnitude upon their environment. For any given species, an environment’s carrying capacity is the maximum load it can support indefinitely—i.e., without reduction of that environment’s suitability for continuing to support that kind of load.1

Humans, as truly as any other type of creature, impose a load upon the environment they inhabit, because any organism needs to withdraw sustenance materials therefrom and, after making life-sustaining use thereof, to dispose of materials metabolically transformed. Because of this, carrying capacity is a concept too essential to remain confined within the occupational jargon of pastoralists and range managers.

Although withdrawals and disposals made by any one individual of a particular non-human species do not much differ from those of another member of that same wild or domesticated species, among Homo sapiens per capita loads vary enormously between different societies. Each million people in industrial societies impose a vastly greater load than imposed by a million hunter-gatherers.

Our ancestors lived in a world where political leaders did not yet need to know the carrying capacity concept. We now live in a world drastically changed. Truly ethical leaders must, as US President Theodore Roosevelt declared a century ago, protect posterity’s interests. For our descendants to have a future, carrying capacity must become part of the working vocabulary of office-holders at the highest levels of all governments.


Varying resource demands

Per capita resource demands, and per capita environmental degradation, are hugely different in developed countries compared to developing countries. With modern equipment, people engage in prodigious amounts of exosomatic metabolism, or garbage. Devices we use have appetites for fuel and raw materials, and excrete more abundant and varied effluents than are produced by endosomatic conversion of food into sewage. Resource demands of modern people have been technologically magnified. So have their waste streams requiring disposal—becoming contaminants of land, sea, or atmosphere.

A human carrying capacity surplus was a fundamental condition of pre-industrial Earth, capable of accommodating increasing numbers of humans seeking more abundance. Humans multiplied, and the New World today is more densely settled than was the Old World when it began sending excess people to colonize what were perceived as virgin lands. Moreover, many of us, equipped personally or collectively with mechanical extensions, have become colossal in our per capita resource demands and disposal needs. We’ve overloaded our planet.

Carrying capacity deficit

Twentieth-century industrial growth raised standards of living and seemed wonderful—with no consideration given of whether it was sustainable. It converted the former surplus of human carrying capacity into a serious and deepening twenty-first-century carrying capacity deficit. The carrying capacity deficit’s effects can be seen (a) locally in traffic congestion, such as that which obliged several of America’s national parks to substitute shuttle-bus service for visitor-driven automobiles on park roads,2 (b) nationally in the devastating practice of mountain-top removal for access to coal to feed our voracious furnaces, (c) globally in the many perils of climate change due to what we fossil-energy-users have done to Earth’s atmosphere.3

Inhabitants of a planet with a carrying capacity deficit, cannot live as people did in a time of carrying capacity surplus. Political leaders who fail to recognize this will grievously mislead, making bad situations worse—even with the best of intentions.4


1 Catton, William R. Jr. 1980. Overshoot: The Ecological Basis of Revolutionary Change. University of Illinois Press, p. 4.

2 National Park Service Looks at Transit to Reduce Environmental Impacts of Increased Visitors

3 Karl, Thomas R., Jerry M. Melillo, and Thomas C. Peterson (eds.). 2009. Global Climate Change Impacts in the United States. Cambridge University Press

4 Catton, William R. Jr. 2009. Bottleneck: Humanity’s Impending Impasse. Xlibris Corporation.

See also


Author: William Catton