Biodiversity Flashcards
Agriculture
Selective breeding: done to select for certain favourable characteristics reduces genetic diversity.
Destruction of hedgerows: Makes large farms with large fields are cheaper and more efficient to run by easing the moving machinery and harvesting. Hedgerows provide habitats for at least 30 species of trees and shrubs, 65 species of nesting birds, 1500 species of insects and 600 species of wildflowers. These in turn provide food for small mammals. Hedgerows also act as wildlife corridors, allowing animals to move safely between woodlands.
Monoculture: increases the productivity by growing the best crops, which can be sowed and harvested quickly using dedicated machinery. This increases yield and reduces labour costs. It reduces genetic diversity and renders all crops in a region susceptible to disease. Reduces animal species diversity, because there are few niches.
Fertilisers: maintain soil fertility, but they can pollute surrounding groundwater causing eutrophication and killing aquatic animals.
Pesticides: are sprayed on crops to prevent attack by insects and other invertebrate animals, but many pesticides have a broad spectrum, killing a wide range of animals and so reducing diversity.
Herbicides: kill competing plants (“weeds”) that might reduce crop yield.
Deforestation
The Two main reasons humans clear forests are:
To use the land for agriculture, housing, mining or reservoirs
To use the timber for fuel, charcoal, paper or building materials.
Forests have a high biodiversity because a mature forest has many different species of plants in several layers; each adapted to their own conditions of light and nutrient availability. The different plants have different animals feeding on them and living in them; and the different primary consumers have different secondary consumers feeding on the. So forests contain complex food webs with high diversity.
By contrast, a field of crops has very low diversity with very few plants (often just the crop and a few weeds) and so few animals. Deforestation therefore reduces biodiversity.
As the diagram shows, forests have a deeper and more extensive root system, so binding the soil together.
Without this root system, soils can be eroded, leading to desertification (fertile land becomes desert). Forests also have a high productivity: i.e. there is a lot of plant material produced per square meter of land, and a lot of photosynthesis takes place. So deforestation reduces the rate at which carbon dioxide is removed from the atmosphere and so increases the greenhouse effect and global warming.
