Biosphere Contents

2. Diversity

Increasing concerns about the loss of biodiversity in ecological systems reflect a recent awareness of the effects of human activities on the planet

Global climate change and the rapid loss of tropical rain forests are just two factors that have increased the profile of biodiversity concerns in recent decades. Earlier generations of humans also had a dramatic impact. The early human occupation of North America coincided with the extinctions of mammoths and other megafauna, while the spread of Polynesians across the Pacific may have resulted in the extinction of over 2,000 species of birds, almost one fifth of all bird species. Increasingly in this century these effects have been seen world wide, and on an ever increasing scale. Whether the loss of a given species matters to the effective functioning of ecosystems, and to the services that ecosystems provide to humanity, is unclear. Different theories suggest that there may or may not be considerable redundancy in natural systems. Certain species are likely to be especially important ecologically, due to their strong relationships with many other species within the ecosystem. These are referred to as 'keystone species'.

A diverse plant community: a poppy field

Fig trees are keystone species in some tropical rain forests

Can you list some of the threats to biodiversity from human activity?