The number of biological organisms in a given defined environment is a population. In the case of the 7 billion human population effectively confined as of to a small part of a biosphere on the planet earth this raises the issue of population control which is the greatest public health issue of the moment and may not be addressed before Malthusian solutions cause a great die back.
It is often assumed that the mathematical modelling of population change on the planet and at the country has been developed to a pretty accurate degree. In the case of official British population projections at least, this is far from the case
- ↑ Appleby J. Population projections: why they are often wrong. BMJ (Clinical research ed.). 349:g5184.(Epub)