The population of Earth is expected to reach between 8 and 10.5 billion between the years 2040 and 2050.
As the population of the planet increases, the demand for resources grows with it, as does the production of waste and pollution.
Population growth has levelled off in the highly developed countries over the past few decades; but these industrialised states are now supporting the maximum numbers that can be sustained in the short term, and the citizens consume around 30 times as much energy and resources as those of the developing world.
Wealthy, but densely populated countries such as in the UK, depend on overseas imports to feed everyone. People have argued that waste and over consumption by richer countries are more of a problem than population growth itself - if resources were shared more equitably, there would still be enough for everyone's survival.