The processes at work in the world produce landscapes where everything is in a constantly dynamic state. The competition for resources, the interaction of organisms with each other and with inorganic, physical processes, the cycles of carbon, nitrogen and water, together with a wide range of weathering and erosion activities, combine to drive the engine of the biosphere fuelled by the energy of the sun and of nuclear reactions deep in the earth. Out of this endlessly shifting cycle of growth and decay, a myriad of patterns is apparent, evolving at various rates into an uncertain future. Humans are part of this world and contribute to the patterns and processes to varying degrees.
This uncertainty is an important concept, as experience indicates that everything is determined by possibilities and probabilities: the likelihood of a fire burning a forest, of an avalanche burying some animals, of a Volcano erupting and covering an area with hot ash or a hard winter killing a late hatched brood of baby birds. Some of the events that alter the evolution of landscape are more predictable than others, in the sense that they are significantly more likely than unlikely to occur. Some are unexpected, only because we have not experienced them before. Others follow regular, or nearly regular cycles. Few are completely random.