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ECOSYSTEMS

What are ecosystems?Coniferous forestClimate:Low rainfall all year (less than 500 mm),cool summers and below freezingfor the winter months.Vegetation:Trees are evergreen with needles.

Temperate deciduous forestClimate:Rain all year (500–1500 mm),low teperature range,cool summers (15–20°C), mild winters above freezing.Vegetation:Deciduous trees that lose their leavesin winter, shrubs and grasses.

TundraClimate:Very low rainfall (less than 250 mm),short cool summers (6–10°C),long cold winters well below freezing.Vegetation:It is too cold for trees to grow. Grasses, flowers, mosses and lichens.

30°N

30°S

Equator

Tropic of Cancer

Tropic of Capricorn

0 2000 km

Tropical rainforest

Savanna

Polar and high-mountain iceDesert

Mediterranean

Temperate deciduous forest

Coniferous forestTemperate grasslandTundra

Key

DesertClimate:Very dry all year (less than 250 mm/yr rainfall), very hot temperatures in summer (over 40°C), can be very cold at night.Vegetation:Very few plants can survive, only those specially adapted such as cacti, and those with very deep roots.

SavannaClimate:A dry season with several months of very little rain and a wet season with high rainfall,hot in the summer (30°C),warm winters (20°C).Vegetation:Deciduous trees that lose their leaves in winter, shrubs and grasses.

Tropical rainforestClimate:High rainfall all year (over 2000 mm/yr),constant high temperature all year(26–27°C).Vegetation:Very tall trees, high density and great variety, layers of forest with continuous canopy.

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The world’s major ecosystems.Figure 5.22

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An ecosystem is a natural system in which the living parts (animals and plants) and non-living parts (water, air, sunlight, soil and rock) interact and interrelate.

Ecosystems vary in size from a small pond to vast grass plains. They also vary in their type, from barren deserts to complex tropical rainforests. The climate is a major infl uence on the plants and animals that live in an ecosystem. Rain provides water and sun provides heat, which are both essential for photosynthesis and therefore for plant growth.

Energy fl owThe sun provides energy which, along with water and CO2, is made into new plant material by the process of photosynthesis. Where there is plenty of rainfall and sunlight, ecosystems are very productive, for example in the tropical rainforest. However, when they are in short supply – for example, where the conditions are very dry or very cold – there is little plant growth.

Photosynthesis can only take place when the temperature is over 6ºC. However, plants can adapt to survive in these harsh conditions. For example, in desert seeds can lie dormant or inactive until there is a sudden rainstorm and then come to life and quickly fl ower. Baobab trees in the savanna store water in their massive trunks to last them through the dry season.

When new plant growth happens, the energy is passed along the food chain. Herbivores eat green plants and carnivores or predators eat the herbivores or other, smaller carnivores. In reality this happens through quite a complex food web, as plants are eaten by a number of herbivores and carnivores eat several different animals.

Nutrient cyclingNutrients are chemicals that are needed by plants and animals. Rocks are broken down by weathering to form the basis of soil, and this provides some nutrients. Others are added from the breakdown of dead animals and plants by decomposers: fungi, bacteria, worms and other insects. Nutrients dissolved in rainwater are taken up by plants, through roots. The nutrients then become part of the living plant tissue and eventually pass into animals along the food chain. To complete the cycle, when the plants and animals die their nutrients return to the soil by decomposition (Figure 5.23).

Carnivore – an animal that eats other animals, also known as a predator.

Herbivore – an animal that eats only plants.

Nutrients – chemicals used in plant growth.

Photosynthesis – a process by which green plants turn sunlight into plant growth.

key TeRms

1 Write a sentence about how these parts of an ecosystem are linked:

a climate and plants

b animals and plants

c animals and decomposers

d soil and plants

e climate and animals.

2 Plants are specially adapted to their environment. Find out how one plant is ideally suited to each of the six major ecosystems in Figure 5.22.

3 Find examples of two herbivores and two carnivores that live in each of the world’s major ecosystems.

4 What is the major ecosystem in the UK? Are there any examples of this near where you live?

aCTiViTies

Nutrients become part of plant material

Leaves and branches die and fall to the ground

Fungi, bacteria and soil organisms such as worms break down dead plant material and nutrients are released into the soil

Nutrients dissolved in water are taken up by plant roots

The nutrient cycle.Figure 5.23

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ECOSYSTEMS

Why are ecosystems an issue?Ecosystems have been affected by human activity for thousands of years, as people have destroyed the natural vegetation in order to use the land for other activities. In the last 100 years, as the human population has increased, the demand for the Earth’s resources (and the technology to access them) has also increased, and most of the world’s ecosystems have become under threat.

Britain’s ecosystem: what has changed?In 7000 BC, 80 per cent of the UK was covered by a temperate woodland ecosystem: woodland made up of the native species of trees such as oak, ash, elm, beech, lime and alder. Now only 6 per cent of the ancient woodland remains, as woodland has been cleared for farming, industry, roads and settlements. There are still threats to the natural woodland today.

Building a by-passThe A57/A628 connects Manchester with Sheffield and it passes through the villages of Mottram and Hollingworth. The high volume of traffic, including large numbers of heavy goods vehicles, causes long delays and congestion for traffic during peak hours. There is noise, visual intrusion and an unpleasant environment for residents, as well as a high accident rate.

Suggest some alternative strategies to building the by-pass that could result in solving the traffic problems of the Mottram and Tintwistle area. The Campaign to Protect Rural England (CPRE) has suggested some ideas, and you could also see the Save Swallowswood campaign website.

ReseaRCh Link

SwallowsWood

Sheffield

Manchester

Glossop

HadfieldStation

Mottram

Hollingworth

Hadfield

Tintwistle

MottramMoor

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LinkRoad

Peak DistrictNational Park

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A 5.6-km by-pass has been proposed that would go around the villages and link the M67 to the A628 Woodhead Pass (Figure 5.24). The route would pass through Swallow’s Wood. Swallow’s Wood is a nature reserve containing woodlands, meadows, ponds and marsh areas. There has been a long campaign against building the by-pass. However, many people are very keen for it to be built.

Swallow’s Wood contains many species of trees, including beech, birch, oak, and lime, flowers such as orchids and iris, animals such as badgers, voles, bats and hares, and birds such as jay, kingfisher and cuckoo.

Figure 5.25

The proposed route of the by-pass. 1.3 km of the road would pass through the Peak District National Park and also pass through green belt.Figure 5.24

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The Tundra ecosystem: what’s changing?The Arctic tundra is a very inhospitable environment, but its fragile ecosystem is under threat as people are demanding more resources that are found in these areas. Look at Figure 5.22 on page 228 to locate this ecosystem.

Mining in NorilskNorilsk, in Siberia, is one of the northernmost cities on the planet. The average temperature is approximately −10ºC, and can be as low as –50ºC. The city is covered with snow for over 250 days a year. The polar night lasts from December through mid-January, so that the people of Norilsk do not see the Sun at all for about 6 weeks.

Norilsk is situated on some of the largest mineral deposits on Earth and has become the centre of a region where nickel, copper, cobalt, platinum, palladium and coal are mined and smelted. Norilsk is now one of the 10 most polluted cities in the world. A major pollutant is sulphur dioxide, which combines with water in the atmosphere to form acid precipitation, which often falls as yellow acid snow that has been recorded at pH3. As a result there is not a single living tree within 48 km of the nickel smelter.

Much of the reindeer pastureland has been lost; this is because the mosses and the lichens have become poisonous. Some areas are like deserts; the

vegetation has gone and the soil is badly eroded. The lakes in the surrounding area are becoming polluted by streams contaminated by the smelters. People are also affected; the life expectancy of a worker in Norilsk is 10 years less than for the average Russian.

Norilsk is a very remote area. The world needs metals such as nickel and the Russian people need to earn money. Does it matter what happens to the tundra? How could the industry in Norilsk reduce its impact on the ecosystem?

Think abouT iT

1 What are the advantages of building the by-pass in Figure 5.24? What groups of people would support the building of the by-pass?

2 What are the disadvantages of the proposed by-pass? What groups of people would be against the proposal?

3 Do you think it matters if woodland areas such as Swallow’s Wood have roads through them?

4 Describe the tundra food web using the terms ‘plants’, ‘herbivores’ and ‘carnivores’. How does pollution pass along the food chain? Give some examples.

5 Find a map that shows the location of Norilsk, and annotate it to show the characteristics of the ecosystem and how this is being damaged by the industry of Norilsk.

6 Why does the Russian government tolerate the smelter at Norilsk?

aCTiViTies

Watch the fi lm about Norilsk Nickel and study its environmental policy on the company website. Does that change your opinion about nickel smelting in Norlisk?

ReseaRCh Link

People Arctic fox

Reindeer Lemming Arctic hare

Snowy owl

Mosses and lichens

Grasses andlow bushes

Key: Energy flow

The tundra food web is quite simple and very fragile. It is a diffi cult environment for plants and animals to survive in.Figure 5.27

Twenty-four hours a day, 7 days a week, the chimneys of the nickel ore smelter at Norilsk pump out a toxic cocktail of pollutants, causing acid rain and smog.Figure 5.26