The WHO projection would make perfect sense if the REST of the earth’s living community remained stable. Unfortunately, it is NOT remaining stable. In order to sustain a human population of 6 billion humans the rest of the living community is losing upwards of 200 species a day—70,000 species a year.
It is well recognized that we are in a period of mass extinction, for which the vastness of the human population is directly responsible. This fact alone assures us that a human population of 6 billion is not sustainable; the living community (of which we are a part) simply cannot indefinitely sustain a loss of 200 species a day. As our population grows, the number of extinctions will increase, probably geometrically.
At a human population of 12 billion, the number of extinctions might be a thousand a day or ten thousand a day. The fact that OUR population might be stable at 12 billion would not mean that the REST of the living community would be stable—and our survival depends absolutely on its survival.
The “experts” you speak of are still possessed of the ancient (and biologically ridiculous) idea that humanity is a species that is separate from the rest of the living community—and can live independently of that community.
updated: 18 Dec 2003