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"Population, The Elephant in the Room" by Paul Chefurka Stampa E-mail

Peak Oil, Carrying Capacity and Overshoot:
Population, the Elephant in the Room


At the root of all the converging crises of the World Problematique is the issue of human overpopulation.  Each of the global problems we face today is the result of too many people using too much of our planet's finite, non-renewable resources and filling its waste repositories of land, water and air to overflowing.  The true danger posed by our exploding population is not our absolute numbers but the inability of our environment to cope with so many of us doing what we do.

It is becoming clearer every day, as crises like global warming, water, soil and food depletion, biodiversity loss and the degradation of our oceans constantly worsen, that the human situation is not sustainable.  Bringing about a sustainable balance between ourselves and the planet we depend on will require us, in very short order, to reduce our population, our level of activity, or both.  One of the questions that comes up repeatedly in discussions of population is, "What level of human population is sustainable?"  In this article I will give my analysis of that question, and offer a look at the human road map from our current situation to that level.

As I have mentioned
elsewhere, the concepts of ecological science are the most effective tools for understanding this situation.  The crucial concepts are sustainability, carrying capacity and overshoot.  Considered together these can give us some clue as to what the true sustainable population of the earth might be, as well as the trajectory between our current numbers and the point of sustainability.


A sustainable population is one that can survive over the long term (thousands to tens of thousands of years) without either running out of resources or damaging its environmental niche (in our case the planet) in the process.  This means that our numbers and level of activity must not generate more waste than natural processes can return to the biosphere, that the wastes we do generate do not harm the biosphere, and that most of the resources we use are either renewable through natural processes or are entirely recycled if they are not renewable.  In addition a sustainable population must not grow past the point where those natural limits are breached.  Using these criteria it is obvious that the current human population is not sustainable.

Carrying Capacity

In order to determine what a sustainable population level might be, we need to understand the ecological concept of carrying capacity.  Carrying capacity is the population level of an organism that can be sustained given the quantity of life supporting infrastructure available to it.  If the numbers of an organism are below the carrying capacity of its environment, its birth rate will increase.  If the population exceeds the carrying capacity, the death rate will increase until the population numbers are stable. Carrying capacity can be increased by the discovery and exploitation of new resources (such as metals, oil or fertile uninhabited land) and it can be decreased by resource exhaustion and waste buildup, for example declining soil fertility and water pollution.

Note: "Carrying capacity" used in its strict sense means the sustainable level of population that can be supported.  This implies that all the resources a population uses are renewable within a meaningful time frame.  An environment can support a higher level of population for a shorter period of time if some amount of non-renewable resources is used.  If the level of such finite resources in the environment is very high, the population can continue at high numbers for quite a long time.  Though some ecologists may cringe, I tend to think in terms of "sustainable carrying capacity" and "temporary carrying capacity".  In this article I just use the single term "carrying capacity" to indicate the population level that can be supported by the environment at any moment in time.  While not strictly correct, this does simplify and clarify the discussion.

An increase in the carrying capacity of an environment can generally be inferred from a rise in the population inhabiting it.  The stronger the rise, the more certain we can be that the carrying capacity has expanded.  In our case a graph of world population makes it obvious that something has massively increased the world's carrying capacity in the last 150 years.  During the first 1800 years of the Common Era, like the tens of thousands of years before, the population rose very gradually as humanity spread across the globe.  Around 1800 this began to change, and by 1900 the human population was rising dramatically:


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