Discuss the relative importance of physical and human factors in accounting for changes to vegetation over time within ecosystems in the British Isles.
This essay will discuss how vegetation alters over time within the British Isles ecosystems and the importance of both physical and human factors in accounting for these changes. The British Isles is a geographical term which includes Great Britain, the whole of Ireland, and all the offshore islands. It has a temperate climate home to a variety of plants and deciduous woodland. An ecosystem is a self contained system in which several species interact with each other and their surroundings. Physical and human factors are changing these ecosystems over time. Physical impacts can be factors such as succession, changes in climate and diseases. Human factors include farming, development, management and deforestation.
Succession is the original physical factor of change in vegetation with in an ecosystem. Without succession there wouldn’t be any vegetation. The plant succession in the British Isles started with the pioneer plants that colonised the bare ground and could cope with the harsh conditions, examples could be lichen and mosses. The next stage of primary succession is herbs, grasses, flowering plants and these add nutrients and organic matter to the ground which provide a deeper soil so more species can grow and conditions become less hostile. Natural succession continues until it reaches a climax community. This is where the ecosystem reaches a stage in succession where the vegetation is in balance with the climate and dominated by one type of vegetation. In lowland England, oak woodland is the dominant species. Local factors may dominate final succession like geology or drainage and create variation called a poly climax theory.
Our woodland reached natural climax 7000 years ago. However 5000 years ago our Neolithic ancestors began to cut down the trees to clear woodland for agriculture and use the wood as fuel for cooking and to build their homes with. The land they cleared they would have used for growing crops or to keep livestock such as sheep. The soil deteriorated as a result and heather came to dominate the plant community. Sheep grazing was the major form of agriculture in the area at the time and the sheep prevented the re-growth of woodland by destroying any young saplings. This is a type of human activity that has influenced the future of plants that grow in the area, through deforestation, introduction of species and prevention of the plants that these animals eat, from growing.
In the 20th and 21st century, much land has been used for industrialization, including the building of homes, factories and railways. The introduction of these has meant that land has had to be cleared for construction and so many animals and plants lost their habitats. Plants, therefore, grow in urban environments, such as on window ledges, cracks in the pavements or roofs of houses. With the introduction of railways and roads, plants have been able to spread their seeds further and grow on the sides of roads and railways, quite often where they are not disturbed by humans.
From the 18th to the 20th century elm trees were extremely popular. In the early 1920s a mild version of Dutch elm disease was identified in Europe and the UK, but it had very little effect on elm trees. However, in 1967, a new and far more deadly strain arrived in the UK and killed more than 25 million trees in the UK alone. Now very few elms are left in the UK or Europe. This changed the British Isles ecosystems significantly.
A factor effecting vegetation in ecosystems all over the British Isles