Food security means having enough food to feed a population. Several biological factors threaten food security, and sustainable methods must be found to feed all people on Earth.
An increasing birth rate threatens food security in some countries, because there are more people to feed. In developed countries, changing diets mean that scarce food resources are transported around the world. New pests and pathogens that affect farming can destroy crops and animals and reduce the food produced.
Environmental changes also matter. If the rains fail, widespread famine can occur in some countries. The cost of agricultural inputs, such as seed, fertiliser and animal feed, affects how much food farmers can afford to produce. Conflicts in some parts of the world can affect the availability of water or food.