11.6 Factors affecting biodiversity

Question 1

Human influence on biodiversity

Answer 1

• To create enough space for housing, industry, and farming to support the increasing population, humans are severely disrupting the ecology of many areas. The main problems are occurring as a result of:
  1) deforestation: the permanent removal of large areas of forest to provide wood for building and fuel (known as logging), and to create space for roads, building and agriculture.
  2) agriculture: an increasing amount of land has to be farmed in order to feed the growing population. This has resulted in large amounts of land being cleared and in many cases planted with a single crop (monoculture)
  3) climate change - there is much evidence that the release of carbon dioxide and other pollutants into the atmosphere from the burning of fossil fuels in increasing global temperatures
• Other forms of pollution result from industry and agriculture, such as the chemical pollution of waterways

Question 2

Deforestation

Answer 2

• It directly reduces the number of trees present in the area
• If only a specific type of tree is felled, the species diversity is reduced e.g. rosewood is often extracted from rainforests, but less useable trees may be left intact
• It reduces the number of animal species present in an area as it destroys their habitat, including their food source and home
• Animals are forced to migrate to other areas to ensure their survival.

Question 3

Agriculture

Answer 3

• Deforestation: to increase the area of land available for growing crops or rearing animals
• Removal of hedgerows: as a result of mechanisation, farmers remove hedgerows to enable them to use large machinery to help them plant, fertilise and harvest crops. It also frees up extra land for crop growing.
• Use of chemicals such as pesticides and herbicides. Pesticides are used to kill pests that would eat the crops or live on the animals.
• Herbicides are used to kill weeds. A weed is any plant growing in an area where it is not wanted. Weeds are destroyed as they compete with the cultivated plants for light, minerals and water.
• Monoculture: many farms specialise in the production of only one crop, with many acres of land being used for the growth of one species.

Question 4

Climate change: Key findings

Answer 4

• The warming trend over the last 50 years is nearly twice that for the previous 100 years
• The average amount of water vapour in the atmosphere has increased since the 1980s over land and ocean
• Since 1961, the average temp of of the global ocean down to the depths of 3km has increased. The ocean has been absorbing more than 80% of the heat added to climate system, causing seawater to expand and contributing to sea-level rise
• The global average sea level rose by an average of 1.8mm per year from 1961 to 2003. There is high confidence that the rate of observed sea level rise increased from the 19th to the 20th century
• Average Arctic temperatures have increased at almost twice the global average rate in the past 100 years
• Mountain glaciers and snow cover have declined on average in both hemispheres. Widespread decreases in glaciers and ice caps have contributed to sea-level rise
• Long-term upward trends in the amount of precipitation have been observed over many regions from 1900 to 2005

Question 5

Climate change: effects of global warming

Answer 5

• The melting of the polar ice caps could lead to the extinction of the few plant and animal species living n these regions
• Rising sea levels from melting ice caps and the thermal expansion of oceans could flood low-lying lands, reducing the available terrestrial habitats
• Higher temps and less rainfall would result in some plant species failing to survive, leading to drought species becoming more dominant .
• Insect life cycles and populations will change as they adapt to climate change as they adapt to climate change. Insects are key pollinators of many plants, so if the range of an insect changes, it could affect the lives of the plants it leaves behind, causing extinction.