3.1 How ecosystems function & 3.2 Ecosystems under threat

http://www.bbc.co.uk/schools/gcsebitesize/geography/ecosystems/

Ecosystem An environment in which living (biotic) and non-living (abiotic) things are linked togetherBiome A large scale ecosystem with similar vegetation & climate throughoutBiotic Living things (& things that have been alive) e.g. producers, decomposersAbiotic Non-living e.g. sunlight, rockProducer Plants e.g. treedPrimary consumer Eats producersSecondary consumer Eats primary consumerBiodiversity A wide range of living things in an areaDecomposers Break down organic matter e.g. bacteria breaking down leaf litterFood chain Energy passed from producers to primary & secondary consumers e.g. grass eaten by

caterpillar, caterpillar eaten by a birdFood web A network of food chainsNutrients Substances that provide nourishment for growth e.g. minerals, chemicalsHumus Decomposed organic (biotic) matterDeforestation Humans clearing away woodland areasOvergrazing Animals grazing land so much that the grassland is damaged or destroyedDesertification Fertile land turning into desert e.g. due to over grazing or deforestation

Energy & nutrient stores & flows A food web

Savanna biome (semi-arid grasslands)

Climate Wet & dry season. Over 20oC all year round

Soil Thin porous soils that drain easily. Thin humus layer

Plants & animals

Adapt to hot climate & dry season e.g. baobab tree stores water and shallow roots to collect water, wildebeest migrate to graze on seasonal grass

Human use of the semi-arid grassland

How over grazing can cause desertification:

1. Population increases.

2. Herds increase in order to meet the needs of growing population.

3. Larger herds of goats graze on more grass and vegetation.

4. Roots die and no longer bind soil together.

5. Grass dies over a larger area as in cannot regrow.

6. Wind blows topsoil away.

7. Area turns into desert.

How does deforestation cause desertification in the semi-arid grassland?

Removing trees leads to less shade, so soil dries out easily

Supply of organic material is lost e.g. falling leaves, animal waste

No interception by leaves and branches – rain can cause soil erosion

Roots no longer bind the soil together – risk of soil erosion

The Machakos Miracle – successful management of the savanna (semi-arid grassland)

Location Kenya, SE of NairobiPopulation 1930 – 240,000 1987 - 1.3 millionSlope terracing 70% of land in Machakos is terraced. The steps on the slopes reduce surface runoff and

help store waterAfforestation Planting trees provides shade, protects the soil, helps bind the soil and provides a supply of

woodAnimal manure & compost

Used to add nutrients to the soil for free

Selling produce Fruit & vegetables sold in Nairobi. Coffee & tea exported. Money can be invested e.g. fertilisers

Irrigation Pipes used to supply stored water directly to crop

Tropical rainforest ecosystem

Climate Hot – over 25oC all year. Reliable rainfall all year round (low pressure & convectional rainfall)Soils Thin layer of nutrients at soil surface. Rainwater can dissolve and leach away nutrientsPlant & animal adaptations

Adapt to hot, wet climate. Trees have wide buttress roots to make trees stable and collects nutrients from wide area. Epiphytes grow on other trees, drawing moisture from humid air. Spider monkeys have adapted to climb in the canopy

How the tropical rainforest is damaged by human activity

Brazil is world’s leading beef exporter & earns $4bn from exports. Rainforest is cleared for cattle ranches

20% of the world’s oxygen is provided by Amazon rainforest – a global impact of deforestation

HEP dams (e.g. Xingu River) floods rainforest. This kills rainforest and displaces indigenous tribes e.g. Kayapo

20% of Amazon rainforest has been lost in last 40 years

Deforestation damages soil. No shade. Roots don’t bind soil. Soil erosion. Loss of organic matter from e.g. leaves, animal waste

Impacts on climate. Rainwater is no longer intercepted & stored. Less evaporation reduces rainfall (convectional rainfall)

Virunga National Park - conservation and management of tropical rainforests

Location Democratic Republic of Congo (DR Congo)Facts Established 1925, 7800km2, UNESCO World Heritage Site, most biodiverse national park in

Africa, habitat for 220 rare mountain gorillasPlanting trees Over 40,000 saplings planted to preserve ecosystem and preserve mountain gorillasManaging poachers

Electric fences, bloodhounds to track poachers

HEP power Free electricity for schoolsVirunga Alliance Project

Improving lives of local people e.g. 64 new schools, improved clean water access, 23 new health clinics

Mikeno Luxury Lodge

Ecotourism e.g. investment to preserve rainforest, employing local people

UK small scale ecosystem – Spurn Point – a sand dune ecosystem

Spurn Point location East Yorkshire coast, coast of North Sea, Humber EstuaryFormation Long shore drift transferring material southwards from Holderness CoastBenefit to people Nature reserve – wildlife in the sand dunes and salt marsh

RNLI lifeboat station Humber pilots base

Threats to ecosystem Coastal erosion – storms from North Sea erode spit and sand dunes Damage to sand dunes by human use Difficulties of living on an isolated ecosystem

Managing Spurn Point Nature reserve to preserve sand dune and salt marsh ecosystems Groynes & rock armour to reduce coastal erosion ‘Block tile’ road – flexible road on shifting sands