5.2 Agriculture and foodIB Environmental Systems and Societies SL: Revision notes

Land is a finite resource, and the human population continues to increase and need feeding. Marginalised groups are more vulnerable if their needs are not taken into account in land-use decisions.

World agriculture produces enough food to feed eight billion people, but it is not equitably distributed and much is wasted or lost in distribution. Food security is the physical and economic availability of food, allowing all individuals to get the balanced diet they need for an active, healthy life.

Agricultural systems vary because of different soils and climates, and farmers' choices are influenced by many factors. These differences have economic, social and environmental sustainability implications.

Nomadic pastoralism and slash-and-burn agriculture are traditional techniques that have sustained low-density populations. Both need large areas of land, so they cannot feed large, dense populations.

The Green Revolution (Third Agricultural Revolution, 1950s and 1960s) used breeding of high-yielding crop plants with increased and improved irrigation, synthetic fertiliser and pesticides to increase food security.

It has been criticised for its sociocultural, economic and environmental consequences, for example debt for small farmers, falling water tables, pollution and loss of traditional varieties.

Synthetic fertilisers are needed in many intensive systems to keep high commercial productivity, at the expense of sustainability. Sustainable agriculture uses other methods to improve fertility, such as crop rotation, manure and compost.

A variety of techniques conserve soil, with environmental, economic and sociocultural benefits. Examples include terracing, contour ploughing, cover crops, shelterbelts and agroforestry.

Humans are omnivorous. Diets lower in trophic levels are more sustainable, because energy is lost between trophic levels, so more land is needed per unit of food energy from meat.

Current global strategies for a sustainable food supply are to reduce demand and food waste, reduce greenhouse gas emissions from food production and increase productivity without increasing agricultural land area.