There are many examples that demonstrate the scale of our activities. One is the extent of croplands. Around 1700, croplands were basically limited to a few areas in Europe and Asia.

Today, cropland have not only increased in global extent to North and South America and Australia, but also intensity, as is illustrated by the transition from light gray to dark grey and black in many areas all over the world.

With the development of croplands and the extension of other acricultural use in to new areas, the need for irrigation increased, and today, irrigation is a major human intervention in the pre-human mass transport in the global water cycle. In many case, irrigation has had positive side effects, but there are also numerous examples where the diversion of water for irrigation purposes has led to environmental disasters, economic problems, and social conflicts.

With the increased activity of humanity we also see increased impact, side effects, so to say. Let us look at some of the very obvious examples.