According to Magurran (2013), species richness is the total number of species in a sample. Species richness is difficult to quantify due a number of reasons. For one, it is difficult to define what creates a species. Secondly, species can be taxonomically similar but ecologically distinct. Thirdly, there are differentiations surrounding the relationship between ecosystem functioning and native species richness. Furthermore, when it comes to measuring species richness, one will realize that many species are rare and only a few are dominant. In order to determine species richness, it is essential to know of means by which to sample the environment or ecosystem in question. Otherwise, it remains difficult to measure the species richness of that particular ecosystem (Magurran, 2013). For example, if checking for how many different types of trees are there in a forested ecosystem, sampling should not only be done on a small plot, seeing as this will not give full information on the type of trees that are found in the forest. This also becomes difficult when dealing with insect communities.
Species richness is a concept used when determining species diversity and when conducting measurement for a certain species, spatial measures of richness that include alpha, gamma, and beta diversity are used (Magurran, 2013). Alpha diversity is usually expressed by the species richness within that particular ecosystem. For instance, when monitoring how farming practices affect the diversity of native birds in the British countryside, the best way to go about it will be to carry out a comparison within different ecosystems, for instance, unobstructed deciduous wood and then to compare it with arable fields. After having undertaken a transection within each of these two ecosystems and also after having counted the number of species, this gives us the alpha diversity for each ecosystem. For instance, we could give hypothetical numbers to the two ecosystems, assigning the unobstructed deciduous wood the figure 11 and the arable field a figure 7. These two are numerical representations of alpha diversity. The gamma diversity of the species richness, on the other hand, is 18, which is the summation of species in the two ecosystems.
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In his research, Irmler (2012) states that, human activities are the leading cause of changes in the environment of various ecosystems and that this affects animal and plant species. These activities often change or destroy the habitats that are responsible for the sustenance of the existence of both plant and animal species. Scientists have estimated that nearly two thirds of animals and plants that were once actually there, are now extinct due to such like human activities (Irmler, 2012). Due to these human activities, all of which continue to pose existential threat to various species, the concept of minimum viable population size has been re-introduced. This provides the probability of persistence of species for a given period of time while means to save it from extinction are being devised. One of the human activities that has had an impact in as far as causing biodiversity change is concerned, is population increase. The human population has doubled in the past four decades causing pressure on ecosystems. Population increase leads to need for more land for cultivation and increased demand for energy resources. This demand causes people to clear tropical forests so as to create room for settlements and for cultivation.
Moreover, human actions have greatly contributed to water as well as land pollution. For instance, the disposal of large amount of garbage into landfills and the burning of non-renewable resources alter then makeup both of the land and of the atmosphere. Run-off from farms, usually that which is highly concentrated with chemical fertilizers contaminates oceanic waters and has great impact for the organisms that take the ocean for their natural habitat (Irmler, 2012). These processes affect the ecosystems and eventually lead to the loss of exotic aquatic species. Such like environmental stochasticity negatively affects the population sustainability of many species due to the nature of their harmfulness to biodiversity.
The Great Lakes ecosystem is a perfect example of how negative impacts of human activities have deteriorated natural ecosystems ("Great Lakes - National Wildlife Federation", 2016). The ecosystem covers 20percent of the world’s freshwaters and is home to many aquatic animals and plants. It has marshes, wetlands, forests and dune communities that support more than 3500 species of both plant and animal life. Some of the native mammals found in this ecosystem include the gray wolf, black bear, bobcat, Canada lynx, elk, white-tailed deer, and the beaver. However, most of these native animals are nowadays rarely seen in this region, seeing as most of them are now endangered. The Great Lakes is home to a large number of fish species, some which are innate whereas others have been introduced to it.
However, the biodiversity of this ecosystem is threatened by several reasons, two of which are population pressure and pollution. It is estimated that 40 percent of the Canadian population lives along the Quebec-Windsor corridor and those from North America are concentrated along the shores of Erie, Huron, and Ontario ("Great Lakes - National Wildlife Federation", 2016). The resultant high population density promotes industrialization, by so doing leads to environmental pollution. Human activities such as industrialization and burning of fossil fuels are the largest sources of greenhouse gases. Greenhouse gases contribute to global warming and ocean acidification. The Great Lakes are also sensitive to the pollution arising from nitrogenous and phosphoric chemical pollutions, which in turn results from the use of inorganic fertilizers. These compounds find their way into the lakes and result to algal blooms. This fertilization effect interferes with the freshwater of the Lakes and the eco balance ("Great Lakes - National Wildlife Federation", 2016). However, the greenhouse effect is useful since it helps trap some of the energy that keeps the temperatures of the earth at a mild degree suitable for animals, plants and human beings. Without it the temperatures would be extreme, but too much greenhouse gas emission causes these temperatures to increase.
References
Great Lakes - National Wildlife Federation. (2016). National Wildlife Federation . Retrieved 12 October 2016, from https://www.nwf.org/Wildlife/Wild.../Great-Lakes.aspx
Irmler, U. (2012). Effects of Habitat and Human Activities on Species Richness and Assemblages of Staphylinidae (Coleoptera) in the Baltic Sea Coast. Psyche: A Journal Of Entomology , 2012 , 1-12. http://dx.doi.org/10.1155/2012/879715
Magurran, A. (2013). Measuring Biological Diversity . New York, NY: John Wiley & Sons.
