Food production and sustainable resources

Last time

Before we start: last time, in Greenhouse gases, plastics and water pollution, you learned these points. Here they are again on one card. Keep them in mind, because today builds on them.

Feeding eight billion

The world needs more food every year, from the same amount of land. Farmers use fertilisers, pesticides and intensive methods to raise yields. But these have costs for the environment. Today: how food production is increased, the problems it causes, and how forests and fish can be used sustainably.

Raising crop yields

Chemical fertilisers add nitrates and other minerals, so crops grow better and the yield rises. Herbicides kill weeds, which reduces competition for light, water and minerals. Pesticides kill pests that eat the crop. Glasshouses control temperature and light, and can add carbon dioxide, so photosynthesis is faster.

Monocultures

A monoculture is growing a single crop on a large area of land, year after year. Advantages: higher yields, and machines can sow, spray and harvest efficiently. Disadvantages: less biodiversity, more pests and disease spread easily, and more fertiliser and pesticide is needed.

Why disease spreads

In a monoculture the plants are genetically very similar, so they have the same weaknesses. If a disease can infect one plant, it can infect all of them, and the whole crop may be lost. Growing a mix of crops, or rotating them, reduces this risk.

Intensive livestock production

Animals are kept in large numbers indoors, with controlled temperature and plenty of feed. They grow fast, and the cost is lower. Disadvantages: diseases spread quickly, antibiotics are used a lot, and animal welfare is poorer. Large amounts of waste can pollute water, and cattle produce methane, a greenhouse gas.

Food chains and food

Energy is lost at each step in a food chain, so eating plants directly gives more energy than eating animals. It takes many kilograms of grain to make one kilogram of meat, so meat needs more land. This is why a vegetarian diet can feed more people from the same area.

Sustainable resources

A sustainable resource is used so that it is not used up and is available for the future. Forests: cut only some trees and replant others, protect forest areas, and use recycled paper. Fish: set quotas on the catch, use a minimum mesh size so young fish escape, and have closed seasons so they can breed.

Biological control

Instead of chemicals, farmers can release a natural predator of the pest. Ladybirds, for example, eat greenfly. This reduces chemical use, so less pollution, and the pests are not harmful to other organisms. But it is slower, and the predator may also eat other species.