The word “environment” is on everyone's lips at the moment, although, if pressed, few people might be able to explain what is meant by that term. Apart from a general feeling that concern for the environment is a “good thing”, there seems to be little awareness of the conflicts that lie behind the attention now being directed towards a wider understanding of the changes that are taking place in that thin layer of the planet earth in which life is possible, and especially the role that man plays in modifying the biosphere.