BIOSPHERE

Where are the world’s major biomes?

This map shows where these biomes are found around the world:
http://www.bbc.co.uk/schools/gcsebitesize/geography/ecosystems/biomes_rev2.shtml

Biome characteristics

• Tropical forests are found near the equator in Central and South America, parts of Africa and Asia. They are hot and humid and contain a huge variety of plants and animals - around half of all the world's species. The trees are mostly hardwood. The climate is called equatorial.
• Savannah or tropical grasslands are hot and dry, dominated by grass, scrub and occasional trees. They have two distinct seasons - a dry season when much of the vegetation dies back, and a rainy season when it grows rapidly. They are found in central Africa (Kenya, Zambia, Tanzania), northern Australia and central South America (Venezuela and Brazil).
• Desert is the driest and hottest of areas. The world's largest desert is the Sahara in North Africa. Areas of scrub land that border the desert are called desert scrub.
• Mediterranean climates are not too hot or cold. They are found around the Mediterranean Sea, near Cape Town in South Africa and Melbourne in Australia.
• Temperate grasslands are dominated by grass and trees and large bushes are scarce. They have a temperate continental climate - the weather is mild with moderate rainfall. Grasslands include the Puszta in Hungary, the Veldt in South Africa, the Pampas in Argentina and the Prairies in the USA.
• Temperate deciduous forests contain trees that lose their leaves and are found across Europe and USA. The weather is mild and wet. The climate is called temperate maritime.
• Coniferous forests, containing evergreen trees, are found in Scandinavia, Russia and Canada. They have a cool climate with moderate rainfall called cool temperate.
• Mountain areas can be very cold at night and during winter. The growing season is short and at higher levels trees will not grow.
• Tundra surrounds the North and South poles. They have an extremely cold climate, with limited numbers of plants and animals able to survive there.

Human uses of rainforests

Humans intervene in tropical rainforests in order to bring real or imagined benefits to themselves or the local population.

Case study: human intervention in the Amazon

The short-term benefits of clearing rainforest areas include:

• land for agriculture, houses and roads
• jobs for local workers in road building, logging, agriculture, mining and construction
• the generation of income (often in valuable foreign currency) for the LEDC when wood, minerals, and other resources are sold
• scientific investigation into rainforest plants may provide new food sources and medicines

A village in a cleared area of rainforest

These benefits, however, come at a cost. Clearing rainforest threatens the survival of many plant and animal species and can lead to serious environmental degradation. Widespread deforestation damages the whole biosphere (the balance of living and non-living things) with serious long-term consequences.
The case study of human intervention in the Amazon looks at some of the issues around rainforest development.

Positive impacts of human intervention

• Improved transportation - new roads and airports. Better transportation means easier access to raw materials like minerals and timber. Rainforest resources can be transported away and sold.
• Infrastructure, hospitals and education can be improved from the money gained from selling natural resources.
• Profits from selling resources can be used to improve a country's infrastructure. For example, profits from the sale of rainforest resources can be used to build schools and hospitals.
• Raw materials, eg tropical hardwoods such as ebony and mahogany, can be sold for a good price abroad.
• Mineral deposits in the Amazon include bauxite (the main constituent of aluminium), iron ore, manganese, gold, silver and diamonds. Minerals can be sold for high profits.
• Large-scale farming brings money into the country and provides food and jobs for the country's growing population.
• Small-scale farming provides food for rainforest communities and the landless poor of Brazil.

Problems of human intervention

Commercial logging activity

• New roads divide up parts of the rainforest and can cut off connections between different biotic and abiotic systems. For example, a road can stop monkeys such as the golden lion tamarin from travelling to gather food and, in turn, distribute seeds to re-sow plants in the forest.
• Land clearance for farming, transportation and mining can lead to deforestation. Hardwood trees take many years to grow so can be difficult to replace.
• Fertile soils that make farming possible are quickly washed away when the forest is cleared. If soil ends up in rivers, this can lead to flooding.
• Loss of animal habitat occurs when trees are cut down. Hence, deforestation can result in endangering animals and plant life, or even causing them to become extinct.
• Profits from large-scale farming and selling resources often go back to MEDCs or large companies and don't benefit the rainforest communities.

Shifting cultivation

Shifting cultivation is a traditional, sustainable method of agriculture which has been practised by indigenous tribes for centuries. It occurs in areas of the Amazon rainforest, Central and West Africa and Indonesia. Along with other aspects of their culture and traditional way of life, it is under threat from large-scale clearance of the forests.

A burning section of the Amazon in Para State, Brazil

• A small area of land is cleared and the vegetation burned, providing a source of nutrients from the ash.
• For a few years the soil remains sufficiently fertile for the tribe to grow crops.
• When the soil's fertility is exhausted, the tribe moves on and clears another small area of forest.
• The original area is regenerated, as it receives nutrients and seeds from surrounding vegetation.
• As no lasting damage occurs, this method of agriculture is sustainable.
• It is sometimes called 'slash and burn' agriculture.

DESERTS

Deserts are areas with fragile and limited resources. Despite the harsh conditions people live in desert areas, but their need for food and water presents many challenges.

Human uses of the desert in MEDCs

Case study: Las Vegas and the Mojave Desert

Las Vegas is an example of a city which is built in a desert area.
Las Vegas is a fast-growing city - the population is expected to double in 40 years. It is located in the Mojave desert - one of America's smallest and driest deserts, which has 15-25 cm of rain per year.
To cope with the population's demand for water, Las Vegas diverts the water supply from Lake Mead on the Colorado River.

Map of Mojave desert with key locations and states marked

650,000 people live in the desert. In addition the Mojave desert is used by:

• tourists - visiting areas such as Death Valley
• military, as they test out airplanes and train troops
• hikers and rock climbers
• off-road vehicles - including quad bikes and motorcycles making use of the varied terrain
• solar and wind energy generation
• film makers, attracted by the scenery

The Mojave Air and Spaceport

The way deserts are used presents many challenges. The off-road vehicles damage the sensitive desert ecosystem. The growth of urban areas threatens the desert area, and pollutes the air. The demand for water increases. The city officials have encouraged the use of recycled waste water and the removal of water thirsty lawns.
Fibre optic cables are routed through the desert connecting urban areas - disrupting the fragile ecosystem and allowing weeds to grow.

Human uses of the desert in LEDCs

Case study: Thar Desert, India

The desert has a population density of over 80 people per km². (Other deserts have population densities below 10 per km²). There are many mobile sand dunes, and sandy hills.

The Indira Gandhi Canal helps irrigate the land in the Thar Desert

Subsistence farming

The desert area is not very fertile. Soils are quickly drained, and contain few nutrients.
The farming is limited, typically a few animals on more grassy areas and fruit. Most is subsistence farming.

Commercial farming

Commercial farming has been possible since the building of the Indira Ghandhi Canal. This irrigates an area near Jodhpur. Wheat and cotton can be grown. The canal also supplies drinking water.

Mining and industry

Resources such as limestone and gypsum (for making plaster) are found in this desert - and are valuable for the building industry.

Tourism

Tourism is a growing industry, and locals can act as guides and provide transport – such as hiring out camels.

Soil erosion and salinisation

There are many issues when humans use deserts and their surrounding areas.

Soil erosion

This is a problem which affects many areas. When the soil is left bare, the wind can pick up speed due to the flat land and blow away the unprotected soil.

The effects of drought in Africa

The effects of drought in Africa

• The soil is exposed and vulnerable to erosion as a result of the removal of vegetation and overgrazing.
• Trees, which provide protection from the wind and rain, are removed to be used as fuel.
• Nomadic tribes have become more sedentary, which puts pressure on the land where they settle.
• When soil is blown away the land becomes useless for grazing and crops and causes desertification. This is a problem in the Sahel region of Africa. This problem is worsened when restrictions are placed on the movement of nomadic tribes.

Salinisation

Salinisation occurs when the water in soils evaporates in high temperatures, drawing salts from the soil to the surface. These salts are toxic to many plants and make the land unusable. This has consequences such as low yields, poor profits and even starvation. Irrigation of land - when water is brought to land that is naturally dry - can cause salinisation on desert margins.
It is not just physical geography which is affected when humans use desert environments. Culturally, when tourists and new migrants come in culture may be diluted or new languages picked up.

Population pressures

With a growing population there is more demand for food and water. This puts pressure on fragile and limited resources. Overgrazing and overcultivation to provide enough food are two problems caused.

People use deciduous woodlands as a source of timber, for recreation and conserving wildlife. Woodland managers have to maintain a balance between conservation and human activity.

Uses of deciduous woodland

Humans use woodlands in a variety of ways:

• as a resource - wood is used for fuel (firewood) or as timber for buildings
• for recreation - for example for deer hunting or walks
• for conservation

Case study: Epping Forest

Epping Forest is an example of a deciduous forest. It is located in north-east London.

The forest is used by visitors and looked after to help maintain the wildlife and its historic landscape.
Recreational activities here include:

• walking
• horseriding
• cycling
• fishing in the larger ponds and lakes

There are also 60 football pitches and an 18-hole golf course in Epping Forest.

The management of temperate deciduous woodland - Epping forest

A pollarded tree

The City of London Corporation has overall responsibility to manage the forest, which is a site of special scientific interest which protects the trees by law. The management has to balance conserving the land with keeping it open to the public. This is difficult to do.
Traditional management techniques include pollarding. This technique encourages new growth, and maintains the trees for future generations. It is a form of sustainable management in the woodland. Pollarding also encourages birds to nest.
Dead wood is left to rot. Rotten wood is food for fungi and encourages wildlife. Some grassy areas are left uncut to encourage wildlife like butterflies.
The recreational areas for biking and horse riding are marked out. This reduces damage to other areas of the forest.