Ecosystems provide people with a variety of goods and services, such as food, clean water, clean air, flood control, soil stabilization, pollination, climate regulation, spiritual fulfilment, and aesthetic enjoyment, to name just a few. Most of these benefits are either irreplaceable or the technology necessary to replace them is prohibitively expensive.

For example, potable freshwater can be extracted by desalinating sea water, but only at great cost. The rapidly expanding human population has greatly modified the earth's ecosystem to meet its increased requirements of some goods and services, particularly food, freshwater, timber, fibre, and fuel.

These modifications have contributed substantially to human well being and economic development. The benefits have not been equally distributed. Some people have actually been harmed by these changes.

Moreover, short-term increases in some ecosystems' goods and services have come at the cost of long-term degradation of others. For example, efforts to increase the production of food and fibre have decreased the ability of some ecosystems to provide clean water, regulate flooding, and support biodiversity.