Il apparait de plus en plus clairement que nous avons dépassés la capacité de la planète. Les principes écologiques de ce phénomène sont bien connus.
[TheOilDrum] Some of us who examine and discuss environmental matters are constantly puzzled and frustrated by the seeming inability of elected officials, environmental organizations, and environmental and political writers to “get” the nature of our ecological plight. Could it be they’re simply unaware of the ecological principles which enable one to understand it?
- A finite earth can support only a limited number of humans. There is therefore a global “carrying capacity” for humans. A basic definition of carrying capacity is “The maximum number of people, or individuals of a particular species, that a given part of the environment can maintain indefinitely.”
- It is an axiom of ecological science that a population which has grown larger than the carrying capacity of its environment (e.g., the global ecosystem) degrades its environment. It uses resources faster than they are regenerated by that environment, and produces waste faster than the environment can absorb it without being degraded. Some definitions of carrying capacity include this element of environmental degradation. Such a population is said to be in “overshoot.”
- Al Bartlett sometimes writes, “A SELF-EVIDENT TRUTH: If any fraction of the observed global warming can be attributed to the activities of humans, then this constitutes positive proof that the human population, living as we do, has exceeded the carrying capacity of the Earth.” The same can be said of much of the rest of the extensive and growing human-caused ecological degradation we see today, including the breakdown of the web of life indicated by the ongoing Sixth Extinction. It is symptomatic of having exceeded the earth’s capacity to sustain our current numbers for the long term. It is, in fact, proof that under current conditions we have done so.  
- It’s axiomatic, as well, that a population can only temporarily overshoot carrying capacity. It will subsequently decline in number, to return to a level at or below carrying capacity. That is, though a population may grow in size until it is too large for existing resources to sustain it, it must subsequently decline.
- Because it degrades it’s environment, a population in overshoot erodes existing carrying capacity so that fewer members of that species will be supported by that habitat in the future.
- Our extraction of nonrenewable resources such as oil and coal has allowed us temporarily to exceed the earth’s carrying capacity for our species. As these supplies are drawn down, our numbers continue to increase, and ecological degradation progresses, the number of humans will, of necessity, come down. Whether we have a hand in voluntarily and humanely bringing them down, or simply let nature manage the whole thing for us, is up to us.