Our conclusions are

• If the present growth trends in world population, industrialization, pollution, food production, and resource depletion continue unchanged, the limits to growth on this planet will be reached sometime within the next one hundred years. The most probable result will be a rather sudden and uncontrollable decline in both population and industrial capacity.
• It is possible to alter these growth trends and to establish a condition of ecological and economic stability that is sustainable far into the future. The state of global equilibrium could be designed so that the basic material needs of each person on earth are satisfied and each person has an equal opportunity to realize his individual human potential

--The Limits to Growth, Abstract established by Eduard Pestel. A Report to The Club of Rome (1972), Donella H. Meadows, Dennis l. Meadows, Jorgen Randers, William W. Behrens III

All historical eras are shaped by the material and environmental realities of their time. Our own reflects the adjustments society and nature have made to accommodate the unprecedented 6.7 billion human beings now alive. And those changes are dramatic. The planet is warming dangerously as a result of the heat-trapping byproducts of our daily lives. Half of the primeval forests that existed at the end of the last ice age are gone. A mist of mercury and other toxic metals from coal combustion falls continuously on land and ocean, and to eat fish is to absorb these metals yourself. Half of us are now urban, rarely if ever meeting up with creatures wilder than crows, cockroaches, and, in some cities, packs of feral dogs....

What dominates our experience in the first decade of the third millennium are the technologies and institutions we have invented, disseminated, tinkered with, and improved over thousands of years to make human life on such scales possible. We've done well. Not only are more people alive than ever, but most of us live longer than our ancestors did. Quite a few of us spend our entire lives in comfort and with tools and toys that those ancestors never could have imagined.

--Population: What to Do When There Are Too Many of Us

"In 1990 the nonrenewable resources remaining in the ground would have lasted 110 years at the 1990 consumption rates. No serious resource limits were in evidence. But by 2020 the remaining resources constituted only a 30-year supply. Why did this shortage arise so fast? Because exponential growth increases consumption and lowers resources. Between 1990 and 2020 population increases by 50% and industrial output grows by 85%. The nonrenewable resource use rate doubles. During the first two decades of the simulated twenty-first century, the rising population and industrial plant in Scenario 1 use as many nonrenewable resources as the global economy used in the entire century before. So many resources are used that much more capital and energy are required to find, extract, and refine what remains.

"As both food and nonrenewable resources become harder to obtain in this simulated world, capital is diverted to producing more of them. That leaves less output to be invested in basic capital growth.

"Finally investment cannot keep up with depreciation (this is physical investment and depreciation, not monetary). The economy cannot stop putting its capital into the agriculture and resource sectors; if it did the scarcity of food, materials, and fuels would restrict production still more. So the industrial capital plant begins to decline, taking with it the service and agricultural sectors, which have become dependent upon industrial inputs. For a short time the situation is especially serious, because the population keeps rising, due to the lags inherent in the age structure and in the process of social adjustment. Finally population too begins to decrease, as the death rate is driven upward by lack of food and health services."

ENVIRONMENTAL AND NATURAL RESOURCE ECONOMICS, Tom Tietenberg; Harper Collins [p.p.132-134]