7.1 Introduction

For the last several billion years nature has nurtured the planet evolving complex eco-systems (the biosphere) that conserve and recycle energy and materials. Much is to be learned from the study of mature climax eco-systems which demonstrate complex web-like integration, conserving energy, all of which is ultimately derived from the sun as it flows through the system and materials which are constantly recycled, the waste from one natural metabolism being the input of another.

Plants and animals live together in mutually interdependent ways that become increasingly specialized, developing mechanisms for regulation preventing overgrowth or dominance. The wonder of nature is the complexity of this interdependence and how extremely efficient it is at recycling the nutrients essential to life.

Occasional aberrations are triggered climatically, by fire, cataclysmic events or in some other way. Species are wiped out (as were the dinosaurs) and new species or groups of species appear to take over. In the past, however, the biosphere has always come back to a balance characterized by complexity and integration but this can take thousands and sometimes millions of years.

Along came humans. In the last hundred years or so, and for the first time in geological history, we have become masters of the destiny of the unique blue-green planet we live on. We are like no other cataclysmic event, yet we are responsible for many of the changes affecting the geosphere-biosphere from salinity, deforestation and pollution to the global carbon dioxide balance.