Herman Daly, in his 1977 book Steady-State Economics, created the idea of the steady-state economy.  Many environmental activists have taken an interest in this theory, and have sought to use it to further their cause.

Basically, Daly said that there was an absolute limit of efficiency in the use of natural resources and energy supplies.

This idea contrasted highly with the traditional economist's view of the environment.  In the past it had been assumed that even as the population grew, advancements in technology as well as resource substitution would allow people to continue to use natural resources.

Daly challenged that theory, and in doing so, implied that population growth and increases in natural resource use would eventually not be supportable economically.  He felt that the traditional theory of economists was dangerous and arrogant.

To deal with the problems Daly feels will arise in the future, he offers a plan to resolve these difficulties.

First, Daly urges the government to adopt policies that would result in zero population growth.  Second, the government should set a level of goods to be produced.  This level would be based on what resources the environment will allow to be consumed for the purpose of making and repairing these goods.  The government will have to find a level where environmental resources will not ultimately be depleted.  Third, the government should limit the amount of wealth and income any one citizen could have.

Steady-state economics bears many similarities to the idea of sustainable development.  It wants people to understand the limits of natural resources so that the environment is not totally consumed before it is too late.