Biome case studies (WJEC Eduqas GCSE Geography B): Revision Note

Specification Link

The notes on this page cover 3.2.2 of the WJEC Eduqas GCSE B Geography.

3.2.2 - How are ecosystems damaged by human activity?

• How hot semi-arid grasslands and one other ecosystem have been damaged by human activity.

• How processes within the ecosystem have been affected

• The effects of the damage at the local scale, to include the effect on biodiversity, and at the global scale.

Case study: hot semi-arid grassland

Case study: tundra

• 'Tundra' comes from the Finnish word 'tunturi', meaning 'treeless plain'

• There is permanent darkness in winter

• During the summer, the sun never sets

Location

• The biome is found mostly in the northern hemisphere, along the Arctic Ocean's edge in North America and Eurasia, and around Greenland

• Small areas of tundra are found in South Georgia and the Antarctic Peninsula in the southern hemisphere

Annual precipitation

• Precipitation is low, under 380 mm

Annual temperature range

• Winter temperatures can fall to -50°C, while summer temperatures hit 10°C

• The average temperature is between -6°C and -12°C

Food chains and webs in the tundra

• The tundra biome has low biodiversity

  • The tundra biome has about 400 varieties of flowers, but only 48 different animals

• Lichens and mosses dominate the biome

  • These are the producers in the ecosystem

  • No trees grow in permafrost, but small trees appear in warmer, sheltered spots

  • The growing season is short

• The lichens and mosses are eaten by insects and grazing herbivores (primary consumers) such as caribou and hares

• The herbivores are then eaten by carnivores (secondary and tertiary consumers) such as wolves and polar bears

Adaptations

• Plants in the tundra need to adapt to wet summers and dry winters:

  • Summer: The top layer of soil thaws, producing boggy and waterlogged land

  • Winter: Frozen soil and long, dark winters

• Animals need to adapt to cold, dry and snowy conditions, as well as wet summers

• Some animals hibernate to conserve energy and survive the winter

  • For example, the Arctic ground squirrels hibernate for 7-8 months of the year

    • They can survive even if their body temperature drops below freezing

• Animals are well-insulated, and this reduces the amount of energy they have to use to keep warm

  • e.g. thick fur like polar bears or blubber like seals

• Many birds migrate to warmer areas during winter

  • Arctic terns live in the Arctic during the northern hemisphere summer, then fly to Antarctica for the southern hemisphere summer

• Many animals have white coats in winter for camouflage; the colour helps predators sneak up on prey and allows prey to hide in the snow

  • Arctic hares are white, which makes them harder for predators to spot against the snow

• Many animals have physical adaptations, such as short legs, round squatting bodies, layers of fur, and insulating blubber

  • The Musk Ox grows two layers of fur

  • The shorter layer traps warm air

  • The longer layer is over 60 cm long

  • Its hooves are large and tough, allowing it to break the ice and drink the water beneath

• Most plants become dormant to survive the cold, dark winters

• Plants are small and round-shaped to protect them from the wind

• Most plants have shallow roots because the permafrost prevents any further growth

• Leaves are generally small, and this limits moisture loss

  • The caribou moss has hollow stems and will become dormant until the next rainfall

• The warmer, wetter summer is brief, so most plants have adapted to a growing season of just 50–60 days

• They are usually very bright and vibrant to attract as many insects as possible for pollination

• Many plants use underground runners or bulbs instead of seeds to reproduce because the growing season is so short

Interdependence in the tundra

• Living and non-living things in the tundra are closely linked

• If one part changes, the others change too 

• They are 'inter-dependent' on each other for survival

• The cold, dry climate has low biodiversity, making this interdependence fragile and easy to disrupt or damage

• Herbivores, such as reindeer, depend on plants like mosses for survival

  • They also enrich the soil with nutrients through their dung after eating the plants

  • Plants depend on herbivores for reproduction because animals spread seeds in their dung and on their fur

• Carnivores, such as wolves, follow herbivores in their search for vegetation 

• In the summer, the tundra has more plant cover

  • This helps surface plants absorb heat from the sun and keeps the permafrost below from thawing

• Permafrost gives water and nutrients to plants

  • Damage to permafrost causes it to melt, which leads to flooding and halts plant growth

• When the permafrost thaws, it releases trapped greenhouse gases like methane, which increases global warming and alters the climate in the tundra

  • This impacts the plants and animals in the tundra

Nutrient cycle

• Stores in the tundra are quite even

• There is a short growing season

• Decomposition is slow due to the low temperatures

• Uptake of nutrients is restricted to the short growing season

  • Leaching and weathering are low due to low precipitation

• The soil is rich in nitrogen and phosphorus

  • It contains large amounts of biomass and decomposed biomass

  • The soil is infertile even with high levels of nitrogen and phosphorus because these nutrients are trapped in frozen organic matter

Impact of humans on the tundra

• Human activity can have a significant impact on the tundra biome

  • Cold environments are fragile and take a long time to recover if damaged

  • Plant growth is already very slow: If plants are damaged (e.g. by vehicle tyres), they take even longer to regrow, if at all

  • As species are already highly specialised, they would find it difficult to adapt to further change

• Permafrost melt

  • Climate change is one of the main threats to the tundra, causing permafrost to melt, releasing greenhouse gases

  • Permafrost is also melting at an increasing rate due to buildings heating the land, especially around big urban centres

• Oil and gas

  • There are many oil fields in areas such as those around Prudhoe Bay

  • The Trans-Alaska oil pipeline links the oil fields to Valdez, where the oil can be shipped out

    • The pipeline impacts the migration patterns of animals such as caribou

  • Oil drilling increases the risk of oil spills, such as the Exxon Valdez in 1989

    • Wildlife populations took many years to recover from the oil spill by the tanker in Prince William Sound

• Mineral resources

  • Gold, silver, iron ore and copper ore are mined, particularly in the Tintina gold belt region

  • Mining leads to:

    • Damage from heavy machinery

    • Long-term soil and water contamination

    • Infrastructure like roads and pipelines can destroy habitats and impact animal migration.

• Tourism

  • Tourists are attracted to the tundra's wilderness scenery

  • Over 2 million tourists visit Alaska each year

  • Tourists can impact the tundra by:

    • Increase pollution

    • Trampling vegetation

    • Disturbing wildlife

    • Increased infrastructure

    • Erosion and soil compaction