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4.6.4Genetics, Variation and Interdependence

Conservation and Farming — AQA A Level Biology 7402 Revision Notes & Topical Questions

5 min read 9 parts Lesson 36 of 46 1 quiz

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4.6.4 Conservation and Farming — AQA A Level Biology 7402 notes: Evaluate how farming reduces biodiversity and how farmers and conservationists can balance food production with conservation.Farming has transformed natural communities into managed ecosystems that are designed to g…

  • Monoculture
  • Removal of hedgerows and woodland
  • Pesticides
  • Herbicides
  • Fertilisers
  • eutrophication

Part 1 of 7How farming reduces biodiversity

Farming has transformed natural communities into managed ecosystems that are designed to give the largest possible yield of a few species. This lowers biodiversity in several ways:

How farming reduces biodiversity
Monoculture
Monoculture growing one crop over a large area reduces species richness and removes habitats and food sources.
Removal of hedgerows and woodland
Removal of hedgerows and woodland to make larger fields, destroying habitats and wildlife corridors.
Pesticides
Pesticides kill pests and also non-target organisms such as pollinators, and can build up along food chains (bioaccumulation).
Herbicides
Herbicides kill weeds, which are food and shelter for insects and birds.
Fertilisers
Fertilisers increase growth of a few species and cause eutrophication in nearby water, harming aquatic life.
Draining wetlands
Draining wetlands and ploughing grassland remove entire habitats.
Overgrazing
Overgrazing by livestock reduces plant variety and causes soil erosion.

Part 2 of 7Why conserve?

Reasons for conservation include ecological (stable ecosystems, food webs and pollination services), economic (sustainable resources, tourism, future medicines and crop genes) and ethical/aesthetic reasons. Conservation means maintaining ecosystems and the variety of species, and managing them so they can be used sustainably. Preservation is stricter and keeps an area untouched.

Part 3 of 7Balancing food production and conservation

Farmers need yield and profit, so conservation measures have to be practical. Examples:

Balancing food production and conservation
Maintaining or replanting hedgerows
, and leaving uncultivated margins, to give habitat and corridors.
Crop rotation
Crop rotation and intercropping, which maintain soil and reduce pests.
Biological control
Biological control and integrated pest management, instead of constant spraying.
Using organic fertilisers
Using organic fertilisers or applying inorganic fertiliser carefully, away from watercourses.
Not cutting meadows until seeds are set
, with grazing at a low intensity.
Restoring ponds and wetlands
Restoring ponds and wetlands and creating buffer strips by streams.
Setting aside
Setting aside areas of land (wildlife strips, woodland planting) and agri-environment schemes in which farmers receive payments for wildlife-friendly management.

These measures may reduce yield or raise costs, which creates a conflict that is handled by subsidies, consumer demand for sustainable products, and legislation.

Part 4 of 7Other conservation actions

1
National parks and nature reserves, protected by law.
2
Captive breeding, seed banks and re-introduction programmes.
3
International agreements, for example restrictions on trade in endangered species.
4
Education and involving local people, so that communities benefit from conservation.

Management often has to include controlling succession (for example grazing or coppicing to prevent grassland becoming scrub), since many species depend on a particular stage.

Part 5 of 7Evaluating evidence

Questions ask you to weigh economic factors against ecological ones, to interpret data on species numbers on conventional and conservation-managed farms, and to decide whether conclusions are valid (sample size, same conditions, control sites). Always make a balanced judgement and use the data supplied.

Part 6 of 7Case study and evaluation of data

A typical data question compares an organic or wildlife-friendly farm with a conventional farm.

Case study and evaluation of data
It may show that the conservation farm has more species of birds and bumblebees, and greater plant diversity, but a lower yield per hectare.
To evaluate, comment on the size of the difference, whether both farms had the same soil and area, how many samples were taken, and whether the farmer has an economic incentive.
Use figures in your answer, for example calculating a percentage difference.

Another case is woodland management by coppicing.

Case study and evaluation of data
Cutting trees on a rotation lets light reach the woodland floor, which allows flowering plants, butterflies and nesting birds to thrive, and it provides a renewable supply of wood.
If the woodland is left alone, the dense canopy shades out these species and diversity falls.
Grazing of chalk grassland
In the same way, grazing of chalk grassland prevents the invasion of scrub.
Case study and evaluation of data
Conflicts of interest are a theme.
  • Farmers, local people, governments and conservationists all have different priorities,
    • and decisions have to weigh short-term costs against the long-term benefits of sustainable use.
  • Examples of compromise include payments for habitat, certification schemes for sustainable products and educating the public.
Finally, note that reducing the use of fertiliser, in addition to benefiting wildlife, reduces the cost to the farmer and the risk of eutrophication.
A strong answer to an evaluation question gives a judgement, such as that wildlife strips are worthwhile where payments cover lost income, supported by data and by named benefits.

Part 7 of 7Exam-style questions

  1. Describe how modern farming methods can reduce biodiversity. [4]4 marks

  2. A farmer is paid to leave a 2 m uncultivated strip around each field. Explain how this may increase biodiversity but reduce the farmer's income. [3]3 marks

  3. Suggest why it is difficult to conserve a species-rich grassland if it is left unmanaged. [2]2 marks

Key terms

TermMeaning
ConservationMaintaining ecosystems and biodiversity through management for sustainable use.
MonocultureGrowing a single crop species over a large area.
EutrophicationEnrichment of water with nutrients leading to algal growth and oxygen depletion.
Agri-environment schemePayments to farmers for wildlife-friendly management.
Wildlife corridorA strip of habitat linking larger habitats.
Integrated pest managementUsing several methods, including biological control, to limit pests.
SustainableMeeting present needs without damaging future supply.

Avoid these mistakes

1
Saying that all farming is bad for biodiversity. Wildlife-friendly farming can maintain or increase it.
2
Confusing conservation (managed, sustainable use) with preservation (no use).
3
Describing eutrophication without the stepsnutrients, algal bloom, light blocked, plants die, decomposers use oxygen, animals die.
4
Forgetting the economic sideconservation measures have to be affordable for the farmer.

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