Past, current and projected future population growth is outlined. Barring a calamitous pandemic, a further increase in the world's population from 7 to between 8.8 and 10 billion by mid-century is unavoidable. This increase is driven by high fertility in sub-Saharan Africa whose population is forecast to more than double in the next 40 years and by a modest rise of 23 % in Asia's huge population. Beyond mid-century, the range of plausible demographic destinations widens; much depends on fertility rates in the next few decades because they will determine the number of potential reproducers in the second half of the century. Vigorous promotion of family planning, particularly in Africa, is crucial to achievement of population stabilisation. Unchanged fertility implies a global population of 25 billion by the end of the century. In the next few decades the contribution of human population growth to global environmental change is moderate, because nearly all growth will occur in poor countries where consumption and emission of greenhouse gases is low. The implications for food production, and thereby water consumption, are greater. Much of the future need for food will be driven by increased numbers rather than changing diets. Loss of bio-diversity and natural habitats, degradation of fragile eco-systems due to over-exploitation and aquifer deletion are likely consequences. © 2013 Springer Science+Business Media Dordrecht.