A brief history of the impact of humans on the earth's biosphere and a description of the more serious of these lead into a description of a method of quantifying the overall contemporary impact. The world's available biological resources - assessed by global footprinting data published by the Global Footprinting Network in October 2008 - are compared with the demand for more and more energy by the high, medium and low income group countries. The inescapable conclusion is that, without fossil fuels, the planet cannot support the current population of 6.8 billion, except at significantly lower average levels of consumption. As the population is projected to grow to 9.4 billion by 2050, by which time available energy and earth's biocapacity will have diminished due to the adverse effects of global warming, there is an urgent case for encouraging people to limit family sizes to two or fewer children to avoid the worst effects of the intrinsic resource-consumption mismatch. Examples of countries which have already recognized the problem nationally are described to show that such actions are not only possible and successful, but are becoming increasingly necessary.