10.3 Species Diversity and Human Activity

Question 1

Explain how agriculture has reduced species diversity.

Answer 1

The few species possessing desirable qualities are selected for and bred. Other species are excluded, as far as possible, by culling or the use of pesticides. This means that there are many individuals of a few species and so there is a low species diversity in that certain area.

Question 2

Do natural ecosystems have a high species diversity or a low species diversity?

Answer 2

High Species Diversity

Question 3

How does a natural ecosystem differ from an agricultural ecosystem?

Answer 3

• Natural ecosystems develop naturally over time, whereas agricultural ecosystems are controlled by humans.
• Natural ecosystems have a high index of diversity (high species diversity), whereas agricultural ecosystems have a low index of diversity.

Question 4

Why do farmers select a certain species to plant?

Answer 4

Farmers would often select species for particular qualities that make them more productive.

Question 5

Why does the number of these desirable species need to be large?

Answer 5

To be more econimic.

Question 6

Why does the amount of species present in that certain area decrease?

Answer 6

• Any particular area can only suport a certain amount of biomass so if most of the area is taken up by the most desirable species then there is a smaller area available for all the other species. These many other species have to compete for the little resources and space available. Many will not survive this competition and even if the species was to evolve to adapt to the changes, the population of the species would have significantly decreased.
• Pesticides are are also used to exterminate these species as they compete for the light, mineral ions, water and food required by the farmed species.
• = Reduction in species diversity = index of species diversity low in agricultural ecosystems.

Question 7

How has the increased production in the UK been achieved?

Answer 7

• Food production in the UK has doubled over the last 40 years.
• This has been achieved by the use of improved genetic varieties of plant and animal species, greater use of chemical fertilisers and pesticides, greater use of biotechnology and changes in farm practices, leading to larger farms and the conversion of land supporting natural communitiesinto farmland.

Question 8

Give 2 examples of practices that have directly removed habitats and reduced species diversity.

Answer 8

Examples:

• removal of hedgerows and grubbing out woodland.
• creating monocultures, for example replacing natural meadows with cereal crops or grass for silage.
• Filling in ponds and draining marsh and other wetland.
• Over-grazing of land, for example upland areas by sheep, thereby preenting regennation of woodland.

Question 9

Give 3 paractices that has had indirect effect on the removal of habitats:

Answer 9

• Use of pesticides and inorganic fertilisers.
• Escaple of sludge form the silage stores and slurry tanks into water courses.
• Absence of crop rotation an lack on intercropping or undersowing.

Question 10

Give 4 examples of conservation tecniques used to increase species and habitat diversity.

Answer 10

• Maintain existing hedgerows at the most beneficial height and shape. An A-shape provides better habitats than a rectangular one.
• Plant hedges rather than erect fences as field boundaries.
• Maintain existing ponds and where possible create new ones.
• Leave wet corners of fields rather than draining them.
• Plant native trees on land with a low species diversity rather than in species-rich areas.
• Reduce the use of pesticides - use biological control where possible or geneically modified organisms that are resistant o pests.
• Use organic, ather than inorganic, fertilisers.
• Use crop rotation that includes a nitrogen-fixing crop, rather than fertilisers to improve soil fertility.
• Use intercropping rather than herbicides to control weeds and other pests.
• Create natural meadows and use hay rather than grasses for silage.
• Leave the cuttin of verges and field edges until after flowering and when seeds have dispersed.
• Introduce conservation headlands - areas at the edges of fields where pesticides are used restrictively so that wild flowers and insects can breed.

Question 11

Why is it bad if biodiversity is reduced?

Answer 11

Because if biodiversity is reduced the global living system becomes increasingly unstable and we all rely on the global system for food and other resources.

Question 12

Explain why there is a reduction in species diversity when a forest is replaced by grassland for grazing sheep or cattle.

Answer 12

Because forests, with their many layers, have many habitats with many different species, i.e. a high species diversity. Grasslands have a single layer, fewer habitats, fewer species and lower species diversity.

Question 13

Suggest why the draining of ponds on agricultural land might have a greater effect on biodiversity than removing a hedgerow.

Answer 13

Ponds provide a habitat for a wide range of aquatic species that are unlikely to find alternative habitats as aquatic habitats are few and far between. Ponds may be a source of food and water for terrestrial species which may also not survive without them. Hedgerow species are likely to have a larger range of alternative habitats as most of the area around will be terrestrial with other sources of food and shelter and so fewer species are likely to be lost.