7.9 - Food Security

Food security and increasing yields

• The world's human population is rising quickly.
• To keep feeding everyone, the amount of food produced globally must rise as well - so that each person still has enough food that is safe to eat and has the right balance of nutrition.
• Food security - Reliable access to enough safe, nutritious food for everyone.

Why farmers focus on raising yield

• There is a limited amount of land available for farming, and it isn't possible to keep clearing more and more land for crops and livestock.
• So the main way to produce more food is to raise the yield - the amount of food produced from a given area of land in a given time.
• Farmers use a range of techniques to increase the yield of their crops and animals, producing more food from the same area without simply taking over more land.

Fertilisers

• Plants need mineral ions from the soil to grow properly:
  • Nitrogen - For making proteins
  • Phosphorus
  • Potassium
• When a crop grows, it takes these mineral ions out of the soil, leaving the soil short of them for the next crop.
• Farmers add fertiliser to replace the missing mineral ions, or to provide extra - this boosts plant growth and so raises the crop yield.

Natural and artificial fertilisers

• Natural - Such as farmyard manure, slurry or compost. They release nutrients slowly and improve the soil.
• Artificial - Made industrially and usually rich in nitrogen, phosphorus and potassium (NPK). They're easy to apply and their mineral content is easy to measure accurately.

Problems caused by fertilisers

1. If too much fertiliser is applied and it rains, the soluble mineral ions are easily washed off the fields.
2. They leach into rivers and lakes, where the excess nutrients can lead to the death of aquatic organisms.

Pesticides and bioaccumulation

• Pesticides are a form of chemical pest control - sprayed onto crops to kill the pests that damage them.
• Fewer plants are lost, so the yield rises.

Types of pesticide

• Insecticides - Kill insects
• Herbicides - Kill weeds
• Fungicides - Kill fungi

Drawbacks of pesticides

• Often poisonous to humans, so they must be used carefully to keep the amount left in food below a safe level.
• Many harm wildlife that aren't pests, such as bees and ladybirds. This can leave less food for animals higher up the food chain.

Bioaccumulation

1. Some pesticides are not broken down and persist in the bodies of organisms that take them in.
2. When a sprayed plant is eaten, the pesticide passes into the animal, then into whatever eats that animal.
3. At each stage up the food chain, the concentration of pesticide in the organisms increases.
4. Eventually organisms at the top can receive a lethal dose.
5. This build-up of a toxic substance in living organisms along a food chain is called bioaccumulation.

Reducing chemical use - Biological control and GM crops

• Farmers can cut down how much chemical pesticide and fertiliser they need to use in more than one way.
• Two approaches are biological control and growing genetically modified (GM) crops.

Biological control

• Biological control - Using other living organisms to reduce the numbers of a pest.
• This is done in two ways:
  1. Encouraging the pest's natural enemies that are already present
  2. Introducing new natural enemies
• Because no chemicals are involved, the crop is protected from pests without the pollution and food-chain build-up that come with pesticide use.

GM crops

Crops can be genetically modified in ways that reduce the chemicals a farm needs:

• Insect resistance - The crop resists insect pests, so the farmer needs to apply less pesticide.
• Efficient nutrient uptake - The crop takes up soil nutrients more efficiently, so the same yield can be grown with less fertiliser.

In these ways, GM crops act as an alternative to pesticides and a way of reducing the fertiliser a farm needs.