We can distinguish two types of economies: candle-type economies and forest-type economies.
The flame of a candle is a dissipative system. It is a dynamic system preserving its shape by dissipating energy. Obviously a candle-flame is a non-sustainable dissipative system: it is using up a finite amount of wax and then goes out.
A forest is also a dissipative system. It receives energy from the sun. Unlike the candle, it is a sustainable system. Solar energy is absorbed and used by the plants and eventually emitted as diffuse, disordered heat radiation. All the materials in the forest are recycled. Some forests have lasted for millions of years.
Our current economy is of the candle type. It is using up a limited amount of resources. Obviously, the whole system is shrinking. When economists are talking about the growth of the economy, they mean (in the candle model) that the candle will shine brighter. This can be achieved by adding another wick. The light intensity will grow. As a result, the wax is used up more quickly.
Economic growth, we learn, means an increase in the speed of using up our resources, i.e. the speed of economic shrinkage. Economists are used to look at the flames in isolation, instead of looking at the whole candle. They think and tell us and the politicians that the flame must be as bright as possible. The brighter it is, the richer we are. It is like taking money out of your savings and calling it income. The more money you take out, the richer you get. That is the logic of economists.
If you understand that our economy is of the candle-type, you will easily understand that growth is not the solution to any problem, it is the problem. What the economists call growth of the economy (and are always trying to maximize) is the growth of the speed of the destruction of our planet.
The other possibility is a forest economy. The energy comes from the sun. The sun can be used as a source of energy as long as earth remains inhabitable, which would be for several hundred million years if we would not destroy it earlier. All the materials (water, oxygen, carbon, nitrogen, minerals) are recycled. There is some growth (trees and other organisms are growing, species may become more numerous) but organisms and species might also die. There are always many species and many organisms and the growth of each single organism is limited. When a tree dies, the minerals stored in it are absorbed by fungi and returned back to other trees. There is no net growth. The total amount of biomass remains more or less the same over time.
An economy following these principles could be sustained for hundreds or thousands of years. There would be not “economic growth”. Single businesses could grow up to a limit, but there would also be processes to limit their growth and dissolve them again in the end. All raw materials would be recycled completely. All energy would come from renewable sources.
A civilization with a forest-type economy can survive for hundreds or even hundreds of thousands of years. A civilization of the candle-type will be extinguished after a short time.
We have two possibilities: either we change our economy and civilization to the model of a forest, or we will go into oblivion. That is scientist’s logic. It is as simple as that.
(Pictures from http://commons.wikimedia.org/wiki/File:Candle_02.jpg,