GCSE Geography | Small-scale Ecosystems (Ecosystems 3)

Examples of small-scale ecosystems are deciduous woodlands and freshwater ponds.

Freshwater pond ecosystem

A freshwater pond ecosystem is made up of a number of smaller habitats - for example at the centre of the pond there are fish where the water is deep, at the edges in shallow water there will be lots of plants, and on the surface there will be small insects and wildfowl. Around the edges reeds will grow in the water, and grasses, bushes and trees will grow on the banks.

The pond ecosystem is dependent on oxygen and light - and levels of these affect the wildlife found there. At the bottom of the pond there is little light or oxygen, but rotting plants provide shelter so decomposers and scavengers live there; in the middle depths fish breathe through their gills and are the main predators - animals rise to the surface to find food; on the pond surface there is plenty of oxygen, light and food and animals either breathe through their gills, lungs or skin; and above the pond's surface birds and animals breathe oxygen and find food either on the water's surface or on the edges of the pond.

Deciduous woodland ecosystem

Deciduous woodlands are high in biodiversity with thousands of species, including native tree species, such as oak and ash, shrubs such as holly and hazel, ferns and bracken, brambles and hundreds of species of moss and lichens. There are also many species of mammals, birds and insects, along with fungi.

All species in the deciduous woodland are interdependent - the trees have broad leaves which maximise photosynthesis during the summer, and they lose their leaves in the winter in order to conserve their energy. During autumn the forest floor gets covered in a thick layer of leaf litter, which has usually disappeared by spring due to decomposition, returning nutrients from the leaf litter back to the soil, which are then taken up by plant roots and used for growth.

How does weather and climate affect small-scale ecosystems?

The characteristics of the ecosystem itself are dependent on a number of factors such as soil and climate - the vegetation is dependent on weather and climate conditions, for example trees in deciduous woodlands lose their leaves in the winter when there is less sunlight for photosynthesis in order to conserve their energy, and areas further north or at higher altitudes, tend to have coniferous woodlands, where trees have needles instead of leaves, which can withstand the cold and wind more.

Extreme weather events such as heatwaves and droughts can cause devastation to small-scale ecosystems, for example, ponds may dry out. Forests can be damaged by storm events, such as the Great Storm of 1987, which wiped out 15 million trees across England. Flood events can lead to waterways being contaminated by raw sewage which damages marine habitats.

How do humans affect small-scale ecosystems?

Woodlands may be deforested to make way for housing developments, road construction, or to use as timber products, affecting habitats, food chains and the nutrient cycle.

Farming affects small-scale ecosystems in a number of ways...

• Water may be taken from ponds for irrigation, which could lead to depletion of water, killing aquatic plants, fish and other marine life.
• Chemical fertilisers can cause eutrophication which causes algae to grow rapidly, which can starve waterways of oxygen and kill fish.
• Hedgerows are often removed to increase field size to make farming more profitable, which can destroy habitats and alter the balance of food webs.