The discussion of ecology is based on the concept of biocoenoses, the association of different organisms making up a community. Any change in one component will effect change in the others. Man has manipulated nature since prehistoric times, often for the good of an area, but many of man's actions cause pollution and damage, sometimes on a planetary scale, e.g. the hole in the ozone layer. Attempts to put right the damage caused by human activities has often been piecemeal, dedicated to one aspect of the natural world. But the fact that the individual sectors of the environment are intimately related means that only an integrated approach will be effective. The example of acid rain is used to show the integrated nature of the environment and pollution.