Agriculture and food productionIB MYP Biology: Revision notes

Intensive farming aims to produce as much food as possible from a small area of land. It uses large amounts of fertiliser, pesticide and machinery, and often grows animals or crops in large numbers. It can feed more people and keep food cheaper, but it can damage the environment.

Crops take minerals such as nitrates, phosphates and potassium from the soil. When the crop is harvested these minerals are removed. Fertilisers replace them, so plants grow faster and give higher yields.

The environmental cost is eutrophication. When rain washes extra fertiliser into rivers and lakes:

1. Nitrates make algae grow rapidly (an algal bloom), which blocks the light.
2. Plants below die from lack of light.
3. Bacteria that decompose them use up the oxygen.
4. Fish and other animals suffocate.

Pesticides kill pests that damage crops: insecticides kill insects, herbicides kill weeds and fungicides kill fungi. They increase yield and the quality of the crop.

Problems:

• They also kill non-target organisms such as bees and ladybirds, reducing biodiversity and pollination.
• Pesticides can pass along food chains and harm animals at the top, such as birds of prey.
• Pests with natural resistance survive, breed and pass on resistance, so the pesticide stops working.

Monoculture is growing a single type of crop over a large area, year after year. It makes planting, spraying and harvesting efficient and cheap because machines can do it all.

It has costs: a monoculture provides few habitats and food sources, so biodiversity is low. One disease or pest can spread quickly and destroy the whole crop, and the same minerals are taken from the soil each year, so more fertiliser is needed.

Biological control uses living organisms to control pests instead of chemicals. Examples are ladybirds that eat aphids, and parasitic wasps that lay eggs in caterpillars.

Benefits: it targets the pest, leaves no chemical residue and the control organisms breed, so it lasts.

Drawbacks: it is slow, rarely removes the pest completely, and an introduced species may harm native wildlife or become a pest itself.

Greenhouses trap heat and let farmers control temperature, light and carbon dioxide, so crops grow faster and all year round. Pests can be kept out, so less pesticide is needed.

Hydroponics grows plants with their roots in a solution of mineral nutrients instead of soil. It uses much less water because the solution is recycled, avoids soil pests and can be used where soil is poor, such as in deserts.

Costs: the set-up is expensive, heating, cooling and lighting use a lot of energy, and mainly vegetables and fruit can be grown.