The economies of the planet are limited by the availability of natural resources, and the ability of nature to provide services that make the planet habitable.

A recent study on ecosystem carrying capacity and nature's services was released in late March 2005. It is available here.

Historically, any society or culture that has exceeded the carrying capacity of its local environment, has suffered an impoverished decrease or completely collapsed. The statues on Easter Island stand as stark reminders of the consequences of a society overexploiting its resources - competition for the biggest, most impressive statue led to high demand for scaffolding and building materials, and the little island was deforested in no time. (See Ronald Wright, A Short History of Progress for more on this and other examples.) Even through the vast majority of people live in abject poverty, the excessive consumption of the few wealthy nations is more than sufficient to outstrip what resources we have on the planet.

We can only ultimately survive as a culture, or even live well as a species, if we reach a steady state economy that does not use up renewable resources at a rate faster than they can be recreated. This will require some harsh reviews of our cultural values (e.g. the religious sanctity of life in an overpopulated world) and our economic precepts (e.g. that continuous growth is necessary).