ABSTRACT
We all depend upon ecosystems for the food and natural resources that sustain our lives. Most of the resources are renewable because ecosystems supply them on a continual basis. People use the resources and return them to the ecosystem as waste such as sewage, rubbish or industrial effluent. Ecosystems renew the resources by processing the waste so it is once again available for use by people (see Figure 8.1). A continuous supply of energy from the sun is required to do this. Solar energy fuels the cyclic movement of materials through the ecosystem providing all animals, including humans, a supply of renewable natural resources and a repository for their wastes. Human use of renewable resources and return to the ecosystem as waste https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9781849776028/a0066d20-e3f0-4ebc-bc69-502fe74f54ae/content/fig8_1_B.jpg" xmlns:xlink="https://www.w3.org/1999/xlink"/>
