Discuss the relative importance of physical and human factors in accounting for changes to vegetation over time within ecosystems in the British Isles (40 marks)
The British Isles can be found in the Northern Hemisphere where deciduous forest is the main biome. Here physical and human factors have accounted for changes to the vegetation for many years. Human factors can include tourism, agriculture, urbanisation, interception and deforestation. Physical factors can be such things as natural disasters, succession and diseases.
The human factor of interception can vary between many situations. For example, humans can intercept and alter the vegetation through predator control. By reducing the predators which feed upon that particular vegetation encourages the flora to grow and provide habitats or food for another species. This takes place in the Lake District where at times too many sheep graze upon the heather which reduces the amount of food for nesting birds such as Lapwing, Curlew and Merlin. As a control humans intercept by limiting the amount of sheep within the areas and even with other animals such as foxes that are also reducing and altering the vegetation to the area by either culling them or simply removing them. Humans may also stabilise sand dunes as a method of interception allowing vegetation such as Marram Grass to thrive. This factor overall can be very positive; predator control (although it is preventing the climax community forming) allows rare ecosystems such as heather moorland to thrive and through stabilising the sand dunes vegetation is allowed to reach climatic climax continuing to Oak Woodland, this occurs in Ainsdale upon Sefton Coast. This human factor allows the physical factor of succession to take place with the area reaching Oak Woodland allows further biodiversity and creates many more habitats for a variety of species but also benefits humans directly by providing protection to housing properties and other infrastructure from the harsh winds coming off the sea.
Through the human process of urbanisation all vegetation upon the area to be built on is depleted. This is a major factor accounting for the changes in vegetation over the years. Since the 19th Century transport has developed with the formation of roads, railroads and further on to motorways. A major reason for this is that all the countries of the British Isles are known as MEDCs. They are able to afford such advances and continue to develop hence leading on to increased urbanisation through building metropolis’ and increased housing to meet the demand of a high population.
An increased population also leads to increased car usage in MEDCs resulting in larger amounts of pollutants being released into the atmosphere. An example of one of these pollutants being emitted into the atmosphere from industrial practises can be sulphur oxides. These can condense within clouds, be transported across to anywhere in the British Isles and once fully condensed the precipitate formed is acid rain. The acid rain has a negative effect upon all types of vegetation. Many trees- 1 in 4-lose around 25% of their leaves when acid rain falls and the likes of lichens, mosses and fungi are intolerant to the high pH levels so deplete immediately. Acid rain, a human and physical factor combined, alters the vegetation of an area in the British Isles drastically very quickly. It also takes a long time to restore the previous state in the ecosystem.
Another alteration to land use other than urbanisation is the change and increase in agricultural practises. This is a human factor which creates deflected succession by halting the ecosystem disabling it to reach its climatic climax. However, not only is succession deflected, the vegetation has to be completely cleared from the area to provide space and nutrients for the crops to be grown. This decreases the biodiversity of the area as the ecosystem can no longer support many of its native species as...
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