What of global scales? Are there examples of landcover changes that have had global impacts? The answer is most certainly, Yes.

The best understood example of global change took place some 60 million years ago when a large asteroid collided with the Earth. One repercussion of this unimaginably violent event was the injection of billions of tonnes of dust high into the atmosphere where it was spread by the winds to envelop the entire globe. So dense was the cloud, it significantly reduced the amount of sunlight reaching the Earth's surface. The temperature fell, and the photosynthetic capacity of the plant life must have been dramatically reduced. All ecosystems on Earth must have been affected. There was a great and dramatic extinction of plant and animal life. The dramatic extinction of just one group of organisms, the dinosaurs, has been known for almost a decade. The sequence of events - a dramatic change in landcover caused by a rare collision - was not understood until early in the last decade.

This dramatic event was used by scientists to convince the world's political leaders that their strategy of achieving national security by stockpiling nuclear weapons was madness. A group of researchers using computer simulation models demonstrated that, if a nuclear war between the opposing super-powers ever began, there would be no winners, only losers. The great extinction would be re-enacted by human folly. Nuclear warfare would, like the colliding asteroid, inject massive amounts of dust and soot into the atmosphere to produce a Nuclear Winter; a dramatic and sustained drop in temperatures and sunlight level that would persist for years. The landcover of the Earth would be all but destroyed, and massive extinctions of plants and animals would follow.

The demonstration that Nuclear Winter is a highly probable consequence of a nuclear war was a critical turning point for all Life on Earth. It was the convincing presentation of the impacts on global landcover, and the flow-on effects for all living organisms, that laid the foundation for the wholesale nuclear disarmament that is proceeding today.

Nuclear Winter is the most extreme example of how changes in landcover can affect living organisms at the global scale. This book is not about such extreme changes. Nonetheless the landcover changes that we are concerned with are significant.

With the words and images I present, I have to convince you that landcover is important to you, no matter where you live or what you do. I want you to finish this entire book with an understanding of the state of the landcover of your home continent and that of the entire world.

Moreover, I want to encourage you to have a raised awareness of the significance of landcover change, both locally and globally. The type, rate and location of landcover change should be of concern to you. If you ignore it, it will be to your detriment.

That is my personal conviction and why I wrote this book.