The Natural World – Revision Notes

1. The Natural World – Revision Notes

2. What Is the Natural World? • This unit comprises three major concept areas. Weather, Climate and Ecosystems • Weather is the day to day changes in the state of our atmosphere and consists of changes in pressure, temperature, humidity and wind. • Climate is the average weather over a long period of time (e.g. over 30 years) • An ecosystem is a collection of plants and animals that live in the same geographic region adapted to certain climate characteristics (e.g. Tropical Rainforests, Grasslands, Temperate forests)

3. Air Masses and the UK • Air Masses are large bodies of air that have relatively uniform temperature and humidity characteristics. They pick up these characteristics from their source region (where they come from) and the land or sea they travel over when they travel to the UK. • Polar air masses bring cold temperatures to the UK • Tropical air masses bring warmer weather to the UK • Continental air masses pass over land hence are dry • Maritime air masses pass over water hence bring moist air to the UK • What weather would the five air masses on the map opposite bring to the UK?

4. Relief Rainfall • Relief rainfall occurs where moist air is forced to rise over a physical barrier such as a mountain range. • Warm air is carried to the West coast of Britain by our prevailing (dominant) winds, the westerlies. • On the diagram, this air encounters the high land at the Lake District and the Pennines and it is forced to rise above this barrier. • Second, as it rises, the warm air cools with height at a rate of 1°C per 100m. As the air cools water vapour condenses to form clouds and eventually it rains over Britain's highland areas. • As the air descends to the East coast of Britain it warms slightly and there is less rainfall. • This results in a rainshadow on Britain’s east coast • It is for this reason that the West coast of Britain is wetter than the East, Blackpool receives 950mm of rainfall per year, The Pennines 2000mm+, and Newcastle 700mm.

5. Convectional rainfall • This type of rainfall occurs in summer months for the UK and brings heavy rainfall and violent thunderstorms to our country. • Short wave radiation arrives at the earth’s surface and is converted to long wave HEAT energy. • This heat energy heats the air above it. • The now warmed air has more energy and rises through our atmosphere and away from the Earth’s surface in THERMALS which rise as fast as 25m/second. • As it rises, the warm air cools with height at a rate of 1°C per 100m • As the air cools water vapour condenses to form CUMULONIMBUS clouds and eventually it rains over the UK. • These events occur mainly in summer and in the south east of the country.

6. Depressions • These storms affect the UK throughout the year and bring wet and windy weather to the UK. • Warm air (™) migrating north from the tropics meets cold dense air (PM) migrating South from the Polar region. • The warm air is undercut by the advancing cold air and because it has more energy and is less dense is forced to rise upwards at a COLD FRONT • Ahead of this, warm air advances into cold air and is also forced to rise above this denser cold air at a WARM FRONT. • At both fronts air is rising so cooling and condensation take place which eventually results in rain AT BOTH FRONTS.

7. The Weather in a Depression • Here you can see the weather a depression brings to the UK. Note that this is a cross section through the depression. As this storm passes from the West of the UK to the East what changes would occur in our weather?

8. Anticyclones • Anticyclones are areas of HIGH PRESSURE where air is descending. Air is sinking to the earth’s surface in an anticyclone, so condensation does not take place and therefore skies are clear. Winds are very light in an anticyclone and ISOBARS (lines joining areas of equal pressure on a weather map) are far apart. • In WINTER anticyclones bring very cold settled weather to the UK. • In SUMMER anticyclones bring very hot settled weather to the UK, as witnessed in the heat wave of 2003.

9. Interpreting Synoptic Charts (weather maps) What is this weather feature here? What would the weather be like here? Why? What is happening to the air molecules here? What is this feature here? What would the weather be like here? Why? What is happening to the air molecules here? What symbols are there on the map? What do they mean? What are these lines on the map? What can they tell you about the weather on this map? What will this weather system eventually bring to the UK? Where do it’s air masses come from?

10. Maritime and Continental Climates • Kiev and Plymouth are both on the same line of Latitude (50°N) so should have very similar climates. • Looking at the graphs opposite you can see that Kiev is warmer in summer and colder in winter than Plymouth. • In addition, Plymouth receives more rainfall that Kiev, and Kiev has a summer rainy season in contrast to a winter rainy season in Plymouth. This proves they have different climates. • The reason for the different rainfall is that Plymouth is surrounded by ocean water so has more available moisture, hence it is wetter than Kiev. • Winter Depressions bring Plymouth most of its rainfall, in contrast to convections ate Kiev in the summer, hence the different rainy seasons. • Temperature is different because Plymouth is surrounded be water and Kiev is in the middle of a continent, surrounded by rock. Water retains its heat in winter warming coastal temperatures in Plymouth. A warm ocean current called the North Atlantic Drift , also warming Plymouth in Winter. Kiev is surrounded by rock which loses its heat in winter quickly, causing Kiev to be cold. In summer the rock heats quickly, giving Kiev high summer temperatures.

11. Global Distribution of Forest Ecosystems • Tropical forests are found between the Tropics of Cancer and the tropic of Capricorn. Within these two lines of Latitude are found the Amazon forest in South America, Western central Africa, Indonesia and Northern Australia. They are exposed to average temperatures of 30°C which vary little and it rains a lot (over 2000mm per year). • Taiga (temperate coniferous forests) are found in a wide band between 50°N and the Arctic circle. They stretch across Canada, northern Europe (Scandinavia) and the Russian area of Siberia. There are no coniferous forests in the Southern hemisphere because of the lack of land at that latitude. These forests are adapted to cold temperatures. • Temperate Deciduous forests are found between 30°N and 60°N of the Equator in Europe, Asia and North America. They are adapted to areas with a small temperature range, and reliable rainfall. They do not occur in continental areas of Europe because it gets too cold in winter.

12. Adaptations of Taiga forest to their environment • These forests contain species such as Douglas Fir and Scots pine, and can grow to heights in excess of 30m. Each forest contains only one type of tree and has little vegetation on the forest floor because it is dark and the soil is acidic. • Trees are evergreen so can photosynthesise when temperatures rise above 3°C so maximise available sunlight. • Leaves are needle shaped and therefore have a small surface area and are waxy. This reduces moisture lost by transpiration, important as these areas receive little moisture (less than 500mm) • The conical shape of trees give them stability in high winds. • Bendy trunks also guard against high winds. • Branches slope downwards so they do not snap under the weight of snow. • Seeds are protected against cold in cones. • Trees have wide spreading roots in shallow soils. Soils are shallow because of slow rates of decay.

13. Adaptations of Tropical rainforests to their environment • Examples of adaptations of plants to the climate. • Leaves have drip tips to allow the vast quantities of water to run off without damaging the leaf. • Trees grow tall to reach the sunlight. • Lianas and vines hug trees to take advantage of nutrients and sunlight and maximise use of space. • Trees have wide roots and thick trunks to support their size – called buttress roots. • Mosses and ferns grow on the forest floor and can live on low levels of sunlight.

14. Threats and solutions to tropical rainforests This is Papua New Guinea, it is covered in Tropical rainforest. It has over 9000 species of plants, 250 species of mammals and 700 species of birds. It has a really rich biodiversity but this ecosystem is threatened. The population are very poor, there are low levels of literacy (70%) and only 1 doctor for every 12,500 people. The government has allowed widespread use and exploitation of the forest in the past.

16. Threats and solutions to tropical rainforests • Causes of deforestation • Cattle Ranching -where large tracts of land are cut down to make way for low quality grazing land for cattle. The land loses its nutrients very quickly and becomes infertile. • Lumbering/Logging – where the rainforest is cut down to collect high quality hard woods such as Mahogany and teak. The lumberjacks have to clear large areas of forest to access these valuable trees, which are few and far between. • Mining – In the Carajas region of the forest vast quantities of Iron can be found and huge mines have been developed to exploit this valuable resource at the expense of the trees. The rail links needed to transport the iron have also resulted in deforestation. • Effects of deforestation • Increased flooding because trees do not catch the rain any more. • Loss of habitat for the millions of species that live in the forest resulting in extinctions. • Alters the water cycle. • When the trees are burnt down they emit Carbon Dioxide which can contribute to global warming. • Trees emit Oxygen, less trees means less Oxygen for us to breath. • Medical plants and cures are lost. • Indigenous tribes of Amerindians are moved on. • Rare plant and animal species are lost. • Soil erosion is increased.

17. Solutions to rainforest destruction • Solutions/ Alternatives • Shifting cultivation – farmers cut down and burn the vegetation in a small area of land and farm it. When the lands nutrients are used up the farmers move on to another plot of land. This allows the initial farm plot time to recover and for the natural vegetation to grow again. • Use Helicoptersto lift logs out of forest – less damage caused. • Encourage tree planting programmes • Sustainablefarming – planting crops between the forest trees and collecting the forests natural resources through rubber tapping. • Switch to fast growing soft wood trees such as pine.