In order to understand and evaluate the threat that human activity poses to the natural world we must first consider what the natural world consists of and how to describe it. This chapter sets the scene by introducing the term biodiversity and considering how our living heritage is quantified and distributed, both geographically and among taxonomic groups. The different ways in which we value natural resources are also considered to help us understand the need for their conservation.

By reading this chapter students will gain knowledge of how biodiversity has developed historically and how it is now distributed taxonomically and globally. They will also gain an understanding of some of the possible natural causes of these patterns and of the value of natural resources to human civilisation.

What have we got to lose?

Life has existed on Earth for around four billion years, constantly evolving to form the spectacular richness of our current living world. In fact the fossil record indicates that, on average, life has steadily increased in diversity and complexity over time to produce the richness we see today (Box 1.1). We have benefited from this natural richness in so many ways, we ourselves are products of it and we continue to benefit from it. How strange it would look, then, to any historian looking back in several thousand years time, that the most intelligent species on earth should, in such a short period, destroy and degrade the environment on which it depends to the degree we have, and continue to do.