Slowing the rapid growth of human population through strengthened voluntary family planning services would powerfully and inexpensively contribute to improvements in food security and the reduction of the greenhouse gas emissions that cause climate change. A confluence of long-term environmental and population trends is undermining world food availability and driving climate change. These trends include quickening climate changes and difficulty adapting to its effects; widespread depletion of water, soils and fisheries; increased diversion of grains from human consumption to bio-fuel production and livestock and poultry feed; rapid population growth, particularly in sub-Saharan Africa and South Asia; and increasing affluence in middle income countries.