The recognition of the influence of Life, landcover included, on the physical (temperature) and chemical conditions of earth has led to the development of the idea that the biosphere of Earth is acting as one organism. I personally do not subscribe to the Gaia Hypothesis, but I encourage you to read the two references provided because they are exciting and thought-provoking. Before you do, re-examine the image of the entire continent provided in the Dedication. It also is thought-provoking.

Because of this fundamental importance in Life-Support, any changes in landcover will have consequences for living organisms. These consequences can be either benign or detrimental and be influential in the short or long term.

Let us pursue this idea a little further by thinking across a range of scales.

It is easy to imagine that at local scales, ~10 km2, a rare organism that has a very restricted distribution can be rendered extinct by landcover (habitat) change such as clearing of vegetation for agriculture or urban expansion. Rare plants and animals are increasing endangered by this process as human actions expand in their extent and severity of influence.

There are many examples where landcover has been significantly altered on regional scales, ~10000 km2, and this has consequently reduced the abundance and distribution of both plants and animals. Most commonly, landcover modification on regional scales is the deliberate consequence of human activity such as clearing for agriculture.

In the last decade, many examples of regional landcover change have been reported that are the unintentional consequence of human action. The most severe and widespread examples of these have been because of atmospheric pollution, the acid rain of the industrialised countries of the Northern Hemisphere and its devastating influence on the forest ecosystems in particular.