Discuss the Relative Importance of Physical and Human Factors in Accounting for Changes to Vegetation over Time Within Ecosystems in the British Isles
SoilDiscuss 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 their habitats have been reduced. Farmers then go and place herbicides and pesticides upon the crops which can end up polluting the area and altering the vegetation of the ecosystem even further or worse, a neighbouring ecosystem. For example, the chemicals could leak into a local water supply through surface runoff and eutrophication could occur. This is where an algae bloom takes place resulting in the depletion of oxygen disabling plants such as pondweed to respire and therefore die.
These then decompose and with a high build up of toxic chemicals the fish of the freshwater lake or pond then die too. A physical factor which can alter the vegetation of an ecosystem within the British Isles can be natural disasters. There are a range of natural disasters that take place all over the world but the ones most common in the British Isles are forest fires, floods and earthquakes. Irrespective that the value on the Richter scale is usually quite low a lot of vegetation can still be disrupted.
Small plants can be uprooted and even fallen debris from damaged properties can fall upon an ecosystem and damage the already existing plants resulting in another physical factor-secondary succession- leading to other species colonising the land and becoming the dominant species. In addition, forest fires and floods act in a similar way. For example, in 2004 in Boscastle there was severe flooding which resulted from a large amount of precipitation that the water basin just couldn’t hold. This led to increased surface runoff and high saturation of the soil, decreasing it stability.
With much of the soil now being washed away, nutrients included, the vegetation previously there became depleted and died out. When such a thing like this takes place and no plants survive the cause is called the arresting factor. Some industrial practises can also be arresting factors. Clear-felling of a forest is where the whole area is completely uprooted and removed for industrial use such as furniture manufacturing resulting in increased soil erosion and decreased nutrients available to those pioneer communities aiming to colonise the area to create a new ecosystem.
It also disrupts the regulation of the water cycle and the carbon stores. Fragmentation also occurs so not only is the process affecting the plant succession also the population dynamics and the food chains within the fauna. An example of where this all takes place is Bradfield Woods, Suffolk. Another industrial practise (human factor) which alters the vegetation is coppicing. It is a deforestation practise where 20-25 year rotation cycles are set up allowing great biodiversity within the ecosystem as many sections of the forest are at different stages of succession.
However, if left unmanaged succession is allowed to take place and equilibrium is reached resulting in much of the light being blocked by taller trees disabling smaller shrubs and carpet plants to grow decreasing the biodiversity. Coastal erosion can take the form of both human and physical factors. It will occur naturally through the tidal systems of the seas but its rate is increased through the use of water sports such as speedboats, yachts, kayaks, etc. by humans.
These increase the rate of depletion of mudflats and sand dunes leading to alterations in the vegetation of the local ecosystem. These both are natural protection barriers of the flora biodiversity and without them many habitats will be lost and species reduced. It’s the opportunity to carry out such activities as the variety of water sports that attracts people to the area resulting to increased tourism. This then leads to soil erosion through people walking along the coast or within the forest and even riding their bikes or horses around the area.
Blow out can be caused by horse-riding, biking and walking. This erosion can be known as an ‘arresting factor’. The factor stops plant succession before it can achieve dynamic equilibrium. ‘Blow out’ can lead to the destruction of dunes which disables species such as Marram Grass with a complex rooting system to grow as the depth of the sand will decrease. This impact has initially been started from human factors but has been amplified by the physical factors of strong wind.
Diseases are yet another major contributor to altering the vegetation of an ecosystem in the British Isles. These can be brought in from other countries via trading or can occur naturally. For example, Ash Dieback has proven to be very common in the east of England in the last few months resulting in many trees having to be deforested before the disease spread further to neighbouring trees in the ecosystem. This reduction in trees decreases the amount of habitats for the specific fauna and flora to the ecosystem (deciduous woodland), decreasing the biodiversity.
Finally, global warming can alter the vegetation of an ecosystem within the British Isles. The increased temperature over the last few decades has altered the usual patterns of seasons. The Bluebell species usually comes out at the very start of spring as temperatures are beginning to warm up from the harsh, cold winter conditions and are then followed by those species requiring warmer temperatures to flower. However, due to the increased temperatures the Bluebell is being outcompeted by those that usually follow it and is now on the decrease.
As plants can’t adapt as fast as animals do to changes within their environment we run the risk of species becoming extinct due to global warming. On the other hand, new species may develop if the climate of the British Isles does continue to change drastically and could lead to the increase in biodiversity of a specific ecosystem. In conclusion, both physical and human factors have a clear role in altering the vegetation of the ecosystems within the British Isles.
Much of it is unnecessary and could be made more sustainable; this is shown by the reduction in the deforestation by the method of clear-felling and instead replacing it with coppicing and also ‘Plant a Tree’ schemes replacing three for every one cut down. As long as we can monitor and maintain the levels of high biodiversity in the ecosystems and prevent species from becoming extinct then an overall positive outcome can be reached. Both physical and human factors are highly significant to the importance of accounting for the alterations within the ecosystems of the British Isles.