Bioshere and Biomes
The biosphere is the zone where life is found. It extends 3m below ground and 30cm above ground and up to 200m deep in the oceans.
A biome is a very large ecosystem. The rainforests are one biome. Hot deserts are another. The world can be divided into nine major biomes these are:-
- Coniferous forest
- Temperate deciduous forest
- Temperate grassland
- Hot desert
- Tropical rainforest
- Tropical grassland (savannah)
- Other biomes (e.g. ice, mountains)
How climate influences the distribution of Biomes
The location and characteristics of each biome are mainly determined by climate. This is because climatic factors affect the growth of plants.
- Temperature is the most important factor. It varies with the seasons. The length of the growing season depends partly on temperature. Temperature gradually decreases as you move away from the equator. As latitude increase, so does temperature decreases.
- Precipitation is also important. A forest ecosystem with a large biomass, needs lots of rainfall. The rain must also be distributed throughout the year. Precipitation happens in low-pressure belts, where air masses converge (meet) and air rises. The pressure belts change with the seasons.
How local factors affect Biome distribution
As well as global factors such as temperature and precipitation, local factors affect plant growth:
- Altitude: temperatures decrease by 1 degrees for every 100 metres in height. So the top of Mount Kilimanjaro is covered in snow, although it is near the equator.
- Continentality is the effect of distance from the sea and is also important. (Diagram pg41)
- Nutrient-rich environments encourage the growth of ecosystems. Nutrients are supplied by the soil or the up-welling ocean currents. Geology, relief and drainage are also important.
Ways humans degrade the Bioshere
Deforestation: Commercial logging destroys forest unless sustainable forestry principles are used. It affects rates of flooding, soil erosion and humus formation. For example, logging in the rainforests of the Amazon and Indonesia.
Conversion to farmland or urban use:Commercial intensive farming destroys or alters the ecosystem. Urban sprawl destroys ecosystems and encourages wildfires. For Example, wheat farming in the American Prairies has removed natural grassland where bison once grazed, soya beans are grown for biofuels and the urban sprawl of Los Angeles.
Over-harvesting/Overfishing: Over-harvesting cause wild animals to be hunted to extinction and overfishing of some species such as krill, needed as food for fish farms, destroys food chains. For example, big game; such as Tigers (India) and Rhino (Africa) and the Krill population (Antarctica and North Sea) is now managed by quotas.
Mining and energy: Mining cuts away whole hillsides. Opencast mining destroys the surface and restoration is only partly successful, drilling for oil causes surface damage and oil tankers cause oil pollution. For example, the removal of forests for mining iron ore in the Brazilian Amazon, tin mining in Malaysia and oil drilling in Alaska – a very fragile environment.
Ways that Humans degrade the bioshere (continued)
Pollution: Water pollution from sewage, fertilisers and industry and toxic fumes emitted into the atmosphere, destroys species and damage ecosystems. For example, too much silt and nutrients kill fish or coral and acid rain kills forests.
Introduction of alien species: Sometimes we introduce new species deliberately. More usually they arrive by accident e.g. via ships or aircraft. Alien species often breed well and take over. For example, pheasants for shooting, rhododendrons are alien species which poison the soil that other plants won't grow there
Tourism and recreation: Eco-tourism has little impact. But high-density mass tourism in fragile environments disturbs wildlife. For example, the Galapagos Islands are under threat due to tourism.
Global Protection Plans
Countries can get together to develop wildlife conservation treaties. Two examples are:
- The RAMSAR convention on conserving wetlands, signed in 1971 and adopted by 147 countries
- CITES –the convention on International Trade in Endangered Species, signed in 1973 and adopted by 166 countries. The CITES treaty lists the endangered species. The aim is to stop the trade products such as elephant ivory or handbags made from crocodile skin.
International treaties, such as CITES are very difficult to manage, there are so many conflicting interests. However, they do provide a useful legal framework for conservation.
Local and National Protection Plans
National policies can be delivered in a local area, involving local people. For example, Biodiversity Action Plans (BAPs) protect natural vegetation in Great Britain. These plans act at local level. They arose from the Convention of Biodiversity at the 1992 World Summit in Rio de Janeiro.
At a national scale, governments can set up protected areas, which help to conserve, manage and restore biodiversity.
- National Parks in England and Wales: In the National Parks the demand of recreation are managed in some of the most attractive, yet fragile coastal and upland landscapes
- Community forests have been established to provide new areas of trees near major cities.
There are many different types of conservation area, all with different conservation aims.
Governments can also pay farmers to maintain and replant hedgerows and become more environmentally friendly.
- Sustainable – means a process that does no lasting harm to people or the environment
- Evapotranspiration – is when water evaporates from the pores of leaves into the atmosphere. This results in water being drawn up plant stems
- Pressure Belts – are regions of the atmosphere which run around the Earth. They are parallel to the Equator. Some are high-pressure areas. Others are low-pressure areas.
- Biodiversity – is the range of animal and plant life found in an area.
- Gene pool – genetic information contained in living organisms.
- Indigenous people – people who have originated in and lived in a country for many generations.
- Transnational companies – large companies operating in many companies
- Keystone species – species which has a particularly large effect on other organisms.