Assess the relative importance of physical and human factors in causing change in ecosystems (30 marks)
Both human and physical factors impact upon ecosystems due to their holistic nature which means that even small changes in the human or physical environment around them can cause an exponential chain of results. However these factors can be both positive and negative to varying degrees. Some of the most obvious physical factors which cause change in ecosystems can be seen through succession; for example in the sand dune ecosystem in Talacre, North Wales you can see how the vegetation changes with distance from the high mark. The further in land you travel across the sand dunes the more densely the vegetation become and the wider the variety of species that grow there become. This is because the fore dunes have many physical factors which inhibit the growth of flora; there is little soil with almost no shelter from wind or the sun. This means that only very few species can establish and survive here, in sand dune ecosystems the pioneer species is often Marram grass. The growth of the Marram grass changes the physical factors in the area as it provides shelter for other plants and animals and their root begin help to improve the soil structure which is a hugely important factor as without a good soil structure many plants will not grow as they need the soil to drain efficiently and to contain the detrifying bacteria which make nitrogen compounds available for plants. Nitrogen along with other nutrients which are also essential factors for plant growth and development are increased by improved soil structure. The further inland across the sand dunes you travel the better all these factors become which is why the species diversity increase so greatly. The wider the variety of plants which grow in an area then the more ecological niches are created and so the more different species of animals can survive there. The main physical factors which cause change in sand...
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