Ecosystems and Biomes
Biosphere- The part of the Earths surface inhabited by living things.
Ecosystem - a grouping of plants and animals that interact with each other and their local environment.
Biome - a large ecosystem - a grouping of plants and animals over a large area (world scale). The world can be divided into 9 major biomes, each with its own type of vegetation and wildlife. The location and characteristics are 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 slightly on the temperature.
- Precipitation is also important. A forest ecosystem with large biomass, needs lots of rainfall. The rain must also be distrubeted throughout the year.
- Sunshine hours determine the amount of light available for photosynthesis.
- Humidity controls rates of evapotranspiration.
Evapotranspiration: Water evaporates from the pores of leaves into the atmosphere. Resulting in water being drawn up plant stems.
Average temperature is the main factor affecting plant growth.
It gradually decreases as you move away from the equator, as latitude increases temperature decreases.
In the tropics, the suns rays are at a high angle in the sky for the whole year. These rays are concentrated over a smaller area than at the poles.
Concentrated rays mean alot of heat and sunlight.
Plants grow well so there is dense vegetation in the tropics.
In polar areas the suns rays are less concentrated. The lack of heat and light limits vegetation growth. Plants are stunted and low growing.
Precipitation happens in low pressure belts where are masses converge and air rises.
The 2 main areas of year round rainfall occur at the equator and at mid latitudes e.g. the UK. Forests grow in both of these areas.
In polar and dessert areas high pressure zones occur causing very dry conditions.
The whole pattern of pressure changes with the seasons. Mediterranean and tropical areas sometimes become low-pressure zones and experience rainy seasons for nearly half the year.
Local factors effect plant growth:
Altitude: Temperatures decrease by 1 degree C for every 100 metres in height.
Continentality: The effect of distance from the sea. The sea cools nearby land in the hot season and warms it during the cold season. This increases annual temperature range and reduces precipitation.
Nutrient rich environments: encourage the growth of ecosystems. Nutrients are supplied by the soil or from upwelling ocean currents.
Geology, relief and drainage are also important.
Distribution of biomes
Tropical Rainforests: Mostly in a band either side of the Equator as the sun’s rays are concentrated here and there is heavy rainfall.
Deserts: found close to the Tropic lines, sun’s rays are concentrated but the air is dry.
Deciduous: Grows in higher latitudes e.g. UK where the sun’s rays are less concentrated and cooler winter temperatures encourage trees to loose their leaves.
Coniferous: found 60° north where temperatures are so cold that trees have evolved pine needles to reduce moisture loss.
Tundra: found at the Arctic Circle where the sun’s rays have little strength and temperatures remain mostly below freezing.
Role of the biosphere
What the biosphere does for us...
- It regulates the gases that make up the atmosphere - plants absorb carbon dioxide and produce oxygen for us to breathe. (photosunthesis)
- It regulates the water cycle - plants slow the flow of water to rivers and filter water to make it clean.
- It keeps soil healthy for plants to grow - new nutrients are provided by rotting plant material.
Good provided by the biosphere:
- Food: Meat, fish, fruits, nuts and berries.
- Medicines: Vitamins, plants used to make medicines.
- Raw materials: Timber, bamboo, rubber, water.
Due to the large populations our Earth has, the pressure to feed these people has meant that natural vegetation has been replaced with farmland to grow crops. Very few communities survive solely from food the biosphere would naturally produce.
Uses of the biosphere
Different 'players' want to use the rainforest in different ways.
Genetic uses: New strains of crop.
- Gums, resins and oils
Ecological uses: Flood landslide prevention, climate and weather regulation.
- Fuelwood and charcoal
- Building poles and housing
- Fruits and nuts
- Green medicine
Threats to the biosphere
Degradation of the biosphere by human activity.
Direct human impacts:
- Over fishing
Indirect human impacts, pollution and climate change causing:
- Sea temperature rise
- Sea water acidification
- Melting of polar ice caps
- changes in amounts of rainfall
- Stress within ecosystems due to rapid change.
Reasons for rainforest destruction:
- Deforestation: Timber used for buildings, furniture and fuel. Exploited by transnational companies.
- Land needed for agriculture such as growing crops or grazing animals. e.g. ranching for poor-quality hamburger meat.
- Mining and quarrying of minerals for construction industry, jewellery, etc.
- Transport routes
- Building human settlements
- Building dams and power stations to provide power.
- Nutrients lost from soil, surface soil washed away, blocking rivers and reservoirs. Rapid surface run off leads to flooding.
- Loss of wildlife to due habitat destruction. No roots holding soil together, landslides occur.
- Water muddy and unsuitable for drinking.
- Short term economic gain.
Indirect causes of rainforest destruction
Rapidly expanding population: People use fuelwood, more needed.
Economic development: e.g. China and India, further need for industrial raw materials, people consume more food and fuel as living standards improve.
- Global warming too rapid for species to adapt.
- Habitats broken up.
- Habitat change due to rising temp, changing rainfall and rising sea levels.
- Extreme weather events e.g. storms, flood and droughts more commom.
- Species ectinct as they can't migrate fast enough.
- Pests and diseases thrive in rising temperatures.
RAMSAR convention on conserving wetlands. Signed 1971 by 147 countries.
Conserves 2.05 million km2 of wetlands around the world.
Why? Wetlands provide a rich biodiversity with many rare species.
How it is threatened? population growth means wetlands are drained for farmland, also vulnerable to climate change. Management type:international treaty protects important wetlands by law.
National parks UK
What it conserves: areas of natural beauty in the UK - 22,000km2 in 15 parks. Why: important for people's leisure, enjoyment and culture and to preserve wildlife and environment How they are threatened: any development that would degrade the ecosystem, e.g.: mining Management type: each park has its own authority controlling any new development.
Lalo Loor Dry Forest Reserve
What it conserves: 500 acres of tropical rainforest Why: almost untouched rainforest, home to large numbers of animals and plants How it is threatened: clearance for soya production Management type: owner of the land has agreed a conservation deal, volunteers care for the land, run reforestation schemes and sustainable tourism to raise funds.
Biosphere management tensions
Sustainable biosphere management:
- Conserving the biosphere for future generations, by ensuring it isn't used faster than it is renewed.
- Local peoople, so the biosphere still provides them with resources.
- Schemes to educate local people, so they can be involved in decision making.
- Helping local people living in poverty. Sustainable schemes allow local people to make a living from ecotourism, or by carrying out activities in the buffer zone.
- Being environmentally friendly. Hravesting is selective, only large trees logged. Only adult fish are caught.
- People and communities will want to make money
- This will often involve using the biosphere.
- Tensions will arise because they will most likely damage the biosphere in the long-term.
- This would mean it's not sustainable economically either, and it would compromise the lives of people living now and future generations
- Everyone needs to benefit and not at the expensive of another person for something to be socially sustainable, including future generations
- Socially sustainable also means consulting people on an equal basis.
- There may also be economic tensions as some businesses may flourish at the expensive of others.
- To be environmentally sustainable involves not harming natural resources so they are unable to regenerate or continue long-term.