2.4 Human impact on biodiversity

Define biodiversity

What agricultural practices promote biodiversity?

• Polyculture versus monoculture

• Crop rotation

• Hedgerow conservation and maintenance

• Using predator strips at field margins

• Integrated pest management

• Biological control versus pesticide use

What is monoculture?

Growing only 1 crop species in a particular area

What are the disadvantages to monoculture?

• Species have particular mineral requirements- soil can quickly be depleted

• Specific pests can be established in large numbers

• Replaces diverse habitat- reducing biodiversity

What is Polyculture?

Planting a variety of crops through:

• Intercropping (range of crops at the same time)

• Crop rotation (different crop species in an area over a number of years)

What are the advantages of crop rotation?

• Supports species diversity

• Lower chance of soil becoming depleted in a mineral

• Can prevent the completion of a pest life cycle- harder for populations to become established

What are hedgerows?

Barriers in farms to restrict movement

Why are hedgerows important?

• Act as wildlife corridors- facilitating movement & dispersal if many species

• Provides a natural habitat

• Protects soil

• Provides food for animals

How to conserve and maintain hedgerows:

• Allow it to grow to maturity at intervals- variety of niches

• Trimming every 2-3 years- maintains nesting sites. allows berries to be produced for food

• Trimming during Jan/Feb- avoid destruction of nests & allowing berries in autumn

• Maintaining range of heights & widths (staggered trimming)- wide range of habitats & allows light in some areas

What is biological control?

Use of specific predators/parasites of the pest to reduce pest population

Release of sterile males which ‘mate’ with females but no offspring are produced

Advantages of biological control

• Very specific

• Won’t harm biodiversity

• No pesticides

Disadvantages of biological control

• Must be carefully researched to not destroy the ecosystem

What are predator strips?

An ungrazed margin of grassland at field perimeters

• Provides a habitat for a range of predators (eg beetles)

Name advantages & disadvantages of predator strips

• Natural predators used rather than pesticides

• Increases biodiversity

• Money lost due to lack of space often is returned as less pesticides are used

• Less space for crops- so less money

What is integrated pest management?

More than one element of pest control in order to balance pest reduction with care of the environment

Chemicals used sparingly

Biological control managing the bulk of the pest population.

Name the methods used in IPM

• Biological Control

• Crop rotation

• Occasional use of narrow spectrum pesticides (target specific pest)

• Growing crops with better pest/disease resistance (through GM/selective breeding)

• Sterile males of pest species so no offspring produced

Advantages of pesticide use

• Cheap

• Easy to use

Disadvantages of pesticide use

• Destroys biodiversity

• Kills species other than target species

• Enables pest resurgence is natural predators killed

• Killing weeds can affect those further down food chain

• Non biodegradable ones build up in food chains- bioaccumulation

• Pest resistance

Name intensive agricultural practices & their effect

• Monoculture

• Increased use of artificial fertilisers

• Remove of hedgerows (for more space for efficient farming)

• Increased dependency on pesticides

Increased food production, as well as economic benefits, but have biodiversity costs

What do fertilisers do?

Whis Biological Oxygen Demand?

The amount of oxygen required by bacteria to metabolise the organic material in a sample of water.