3. Causes of pollution

Two main trends are correlated with pollution levels:

• the development of technology, which has led to significant disruption of natural energy flows, and then to disruption of the materials cycle, producing increasing quantities of non-recyclable waste;

• the demographic explosion: it took more than two million years for the human species to reach one billion individuals, a figure it reached in the 19th century (table 1 ). It took just 120 more years to reach the second billion, thirty more for the third billion, fifteen for the fourth billion and twelve for the fifth. In 1999, humanity reached 6 billion people, six times more than at the beginning of the 19th century, and 6.1 billion by the end of 2000. 7 billion people are expected by 2012....