What are sustainable limits? This article has three simple guidelines that define the sustainable limits to material and energy use.

Sustainable limits

The economist Herman Daly suggested three simple guidelines that define the sustainable limits to material and energy use:

For a renewable resource – such as soil, water, forest, fish – the sustainable rate of use can be no greater than the rate of regeneration of its source. (For example, fish are harvested unsustainably when they are caught at a rate greater than the rate of growth of the remaining fish population.)

For a non-renewable resource – fossil fuel, high-grade mineral ores, fossil groundwater – the sustainable rate of use can be no greater than the rate at which a renewable resource, used sustainably, can be substituted for it. (For example, an oil deposit would be used sustainably if part of the profits from it were systematically invested in wind farms, photo-voltaic arrays, and tree planting, so that when the oil is gone, an equivalent stream of renewable energy is still available.)

For a pollutant the sustainable rate of emission can be no greater than the rate at which that pollutant can be recycled, absorbed, or rendered harmless in its sink. (For example, sewage can be put into a stream or lake or underground aquifer sustainably no faster than bacteria and other organisms can absorb its nutrients without themselves overwhelming and destabilizing the aquatic ecosystem.)

Sustainable limits