Farming and conservationAQA A-Level Biology: Revision notes
Section 1
How farming affects biodiversity
Farming turns diverse natural habitats into land that produces a few crops or animals. Modern intensive farming has therefore reduced biodiversity. The main techniques that do this are described below, together with the reason each one has this effect.
Section 2
Habitat loss and monoculture
- Removing hedgerows to create bigger fields destroys habitats, nesting sites and the corridors animals use to move between habitats.
- Monoculture means growing one crop over a large area. It supports few plant species, so there are fewer niches and fewer food sources for insects and other animals.
- Draining wetlands and filling in ponds removes aquatic habitats, so species such as amphibians and dragonflies are lost.
- Clearing woodland for farmland removes habitats for woodland species.
Section 3
Chemicals and grazing
- Herbicides kill wild plants (weeds), so insects lose their food and habitat.
- Pesticides kill insects, including harmless ones, so insect-eating birds and other animals have less food.
- Inorganic fertilisers favour a few fast-growing plants, which outcompete other wild plants and reduce plant species richness.
- Overgrazing and trampling by too many animals remove plants before they can flower and set seed, reducing plant diversity.
A fall in plant species leads to a fall in the animal species that depend on them, because food chains are shortened.
Do not just write that farming 'kills animals'. Explain the chain: the chemical or change removes a food or habitat, so the dependent species decline.
Section 4
Conservation measures on farms
Farmers can reduce their impact while still farming:
- leaving uncultivated field margins where wild plants grow
- replanting hedgerows and restoring ponds
- using crop rotation and growing a variety of crops
- reducing pesticide and fertiliser use and using biological control
- reducing stocking density, so grassland is not overgrazed.
Section 5
The balance between conservation and farming
Food production is essential to feed the population and provide farmers with an income. Conservation protects biodiversity, which is valuable for ethical, ecological and economic reasons. The two can be balanced:
- Payments and grants compensate farmers for the area or yield they lose.
- Only small areas need to be set aside, so most land is still used for food.
- Wildlife helps farming: pollinators and the natural predators of pests can raise yields or reduce costs.
A good answer gives points on both sides and ends with a justified conclusion.
That's the notes covered.
Carry on to the next subtopic.
Exam questions on Farming and conservation
- A farmer removes the hedgerows that divide several small fields, creating one large field. The whole field is sown with wheat every year, and the farmer sprays it with a herbicide and an insecticide.Explain how spraying the field with a herbicide and an insecticide would reduce the biodiversity of the farmland.2 marks
- A hill farmer increased the number of sheep on a grassland from 2 to 12 per hectare. The farmer also began applying inorganic nitrate fertiliser every spring to increase grass growth.Suggest why a fall in the number of plant species on the hill could lead to a fall in the number of insect species.2 marks
- A farm manager joins a government scheme that pays farmers to leave uncultivated margins around the edges of their fields, to replant hedgerows and to stop spraying insecticide near the hedges. The margins will take up 5% of the farm's cropland.Explain how the measures in the scheme would increase biodiversity on the farm.3 marks
Written by the Exaim team, led by Shaun Daswani (Head of Upper Secondary, Improve ME Institute; MSc Financial Mathematics, Imperial College London; BSc, UCL) and Jason Daswani (operational lead, Improve ME Institute; LSE).