B18.1 The human population explosion

Biodiversity and why it matters:

Biodiversity is a measure of the variety of all the different species of organisms on Earth, or within a particular ecosystem. In general, a high biodiversity ensures the stability of ecosystems. It reduces the dependence of one species on another for food, shelter, and the maintenance of the physical environment. As you have already seen, if there are relatively few species in an ecosystem and one is removed in some way, it has a dramatic effect on other species. If there are lots of different types of organisms, the loss or removal of one species has a limited effect because others take its place. 

Scientists now realise that the future of the human species on Earth relies on us maintaining a good level of biodiversity. Unfortunately, many of our activities are reducing biodiversity, and we have only recently started attempts at halting this reduction.

Human population growth:

For many thousands of years, people lived on the Earth in quite small numbers. There were only a few hundred million people. They were scattered all over the world, and the effects of our activities were usually small and local. Any changes could easily be absorbed by the environment where they lived. However, in the past…