That is all that needs to be said about climate driven landcover change. The dynamics of this type of global landcover change are repetitive in time but very diffuse in space. For example, the greenness change for the Australian continent follows a general pattern each year but the variation between years is quite noticeable.

The patterns of greenness change can be related to the physiological activity taking place in the landcover. Over time scales of months, the observed changes are closely related to the flow of solar energy and water; the predominant climate factors of temperature and precipitation.

Over time scales of years, trends in these landcover changes can be related to the biogeochemical cycling of Carbon, Nitrogen, Oxygen and so forth, between the surface and the atmosphere.

Together these flows represent the functioning of a complex but regulated system. The patterns of greening are thus indicators of the condition or health of the Earth. The climate-driven dynamics of landcover condition uniquely captured by space data, can now be closely monitored for trend.

Is it possible to detect a response of the entire Earth system to the changes in the concentration of greenhouse gases generated by humankind? If so, are these changes deleterious or benign, and are they reversible?

These are significant questions for all who travel on spaceship Earth.

While these images of the whole of Earth are fresh in our mind, let's continue with this global reasoning and discuss the other type of landcover change.

Unlike the climate-driven seasonal change in landcover activity discussed above, this type of change is disjunct in time and space and is entirely and directly generated by human action.

It is not just a change in function and activity. Rather it is a change in structure and floristic composition fromwhich flows altered function and activity. In this type of change, landcover is transformed by landuse almost always in an rreversible way. Forests become grasslands; woodlands and savannas become croplands; and grasslands become deserts.

This type of landcover change is the focus of this book. It will put the remaining chapters in perspective if we continue to think about this topic on a global level.