This essay outlined a debatable question associated with humanity which is the greatest threat to global biodiversity. Biodiversity exists abundantly in the form of plants, animals, and organisms that is imperative to satisfy our basic needs. However, it is widely threatened over the years, and many organisms have gone into extinction due to various activities frequently driven by humans. Numerous species and ecosystems are being put to the threat of destruction with a higher rate of extinction. In fact, the technological advancement has transformed the world that leads to deforestation & habitat revolution, food demand, overexploitation, the introduction of invasive species and pollution. These all are key drivers contributing in the devastating effect of biodiversity loss. Moreover, it also caused habitat loss, fragmentation, a disorder in inland water ecosystems, and degradation affecting biodiversity. It upsurges unsustainable water use and inadequate land uses such as settlement and agriculture. In addition, habitat loss is triggered in the coastal ecosystem due to climate change and ocean acidification. These drivers regarding biodiversity loss are engineered and driven by humans apart from naturally induced factors, but human activities surpass the natural causes in driving these changes. The regulatory actions and various strategic measures have been introduced to eradicate these terrible effects on biodiversity, but it needs more concerted efforts and its implementation. A lot has to be done to deal grievous loss in biodiversity and save the earth due to human activities.
Human Activities and Global Diversity
The term Biodiversity (or biological diversity) encompass the variety of life on Earth. Biological diversity has to do with the several millions of species that live on the planet together with their genetic species. It also relates to the lots of ecosystems in which these species make unique communities and interact with not only each other but the soil, water and air (American Museum of Natural History, 2016; WWF, n.d). The biodiversity does consider not only rare, endangered or threatened species but also every living thing including organisms about which have limited knowledge such as fungi, microbes, and invertebrates (AMNH, 2016).In other words, we can find biodiversity everywhere, and Figures 1, 2 and 3 are presenting a count of species that are under threats including plant, animals and organisms. Moreover, biodiversity is imperative because we require it to satisfy our basic needs such as fuel, drinking water, food, shelter, and medicine (AMNH, 2016; Turnhout, Dewulf & Hulme, 2016). However, biodiversity is largely threatened, and many organisms have gone into extinction due to various activities mostly driven by humans. However, an interesting question still presents itself ‘is humanity the greatest threat to global biodiversity?’ This question is debatable and of course, many scholars have boldly asserted it to be true. Hence, this essay deeply considers the contributions of humanity which threating a loss in biodiversity.
Figure 1Reported species of animals and their number facing human threats. Adapted from University of Michigan (2006)
Figure 2 Graphical representation of reported species of plants and their number facing human threats. Redrawn from source, University of Michigan (2006)
Figure 3 Bar chart representing existing species of organisms. Redrawn from source, University of Michigan (2006)
One of the major avenues for biodiversity loss is extinction. Over the years, millions of organisms that lived on the earth have gone into extinction. Based on geological perspective, extinction is a natural event and repetitive. Over the past 200 million years, the average rate of extinction has been 1 – 2 species per year and 3 – 4 families per million years (University of Michigan, 2006). However, the trend and picture painted here seem to take a different shift in the modern time owing to human activities. Numerous species and even ecosystems are being put to the threat of destruction with a rate of extinction that has not been recorded in the history. Virtually all kinds of species have been threatened by human activities resulting in huge loss of biodiversity. Besides the rate at which human population is growing is itself an important factor in evaluating diversity loss. Appendix-A is illustrating a comprehensive overview of factors and threats faced to biodiversity from the human activities.
The pattern of extinction can be studied by considering human migration from Africa since prehistoric times, 8,000 to 90,000 years ago. On another hand, the recent trend can be seen by taking a look at the way in which elephant birds, hippos, and large lemurs were driven extinct when humans colonized Madagascar. The human population grew enormously from 1 billion in 1800 to 2 billion in 1930, 4 billion in 1975 and more than 7 billion today. The rapid explosion of the human population is of special interest here because it has rigorously ruinous consequences on other species on the planet Earth (Center for Biological Diversity, 2016). Moreover, several human activities have been identified that specifically contribute to this devastating effect of biodiversity loss (Petersen et al., 2016). These activities include climate change, deforestation & habitat revolution, food demand, overexploitation, the introduction of invasive species and pollution are all of the human origins and have for years wrecked intensive havoc on the Earth's biodiversity and hence driving lots of species to extinction and causing several other havocs on the ecosystem (Petersen et al., 2016; Petronzio, 2015; Turnhout et al., 2016).
Figure 4 Main drivers causing loss of biodiversity. Redrawn from source, (Convention on Biological Diversity (CBD), 2016)
Biodiversity Loss by Humanly Engineered Activities
Technological advancement driven by human activities has obviously transformed the world. In the bid to advance the world a notch higher and improve the standard of living, man has greatly altered the natural courses and therefore gravely affected biodiversity. Biodiversity loss has become the order of the day, especially in the twenty-first century. Hence, it is pertinent to discuss how these drivers engineered by humans affect the variety of life on earth.
Habitat loss is one of the key direct drivers that affect biodiversity. Too often than not, man modifies the natural environment so as to serve his own good ends and usually, this translates to a loss in biodiversity. In fact, habitat loss was identified by Noonan-Mooney & Gibb (2013) as the most significant cause of biodiversity loss globally. Habitat loss includes activities like draining of wetlands in order to create a way for new development projects, felling trees and cutting down forests for timber, clearing lands for agricultural purposes, damming rivers to provide water for agriculture and cities and so forth. According to IUCN (2010), habitat loss affects 86% of all threatened birds and mammals assessed and also 88% of all threatened amphibians. Moreover, fragmentation is another negative consequence of habitat loss (Segan, Murray & Watson, 2016). This occurs when human activities such as the construction of roads cause changes in a landscape and therefore, results in the separation of parts of the habitat from one another (Utz, 2014). The African elephants found in the Congo basin can be presented as a good example of such species (IUCN (2010).
Habitat loss dominantly associated with deforestation (Devaney, Redmond & O'Halloran, 2015). According to Petronzio (2015), an estimate of 18 million acres of forest is lost each year due to human activities. CBD (2010) also indicated that habitat loss in the terrestrial habitat is primarily caused by the conversion of wild lands to agriculture, and this accounts for up to 30% of land globally. The demand for biofuels has recently driven this cause of biodiversity. Moreover, for inland water ecosystems, habitat loss and degradation is largely caused by unsustainable water use and inadequate drainage for conversion to other land uses such as settlement and agriculture. Moreover, in the coastal ecosystem, habitat loss is largely caused by factors such as mariculture, especially shrimp farms in the tropics (CBD, 2016; Devaney et al., 2015).
Climate change simply emphasizes the alteration of the global climatic patterns. This change is already impacting negatively on biodiversity. As a matter of fact, CBD (2010) projects that it would progressively become a more significant threat in the coming decades. Some consequences of climatic change such as loss of Arctic sea ice put biodiversity to threat across the entire biome and even beyond it. Another consequence of climatic change is ocean acidification (Abbasi & Abbasi, 2011; Sponberg, 2007). This is caused by the higher concentration of carbon dioxide in the atmosphere. Ocean acidification has been shown to drive biodiversity loss in the ocean bodies (Figure 5).
Figure 5 Mechanism of acidification and threat to biodiversity. Source adapted: (Abbasi & Abbasi, 2011)
Climatic change is mostly caused by the accumulation of greenhouse gasses such as carbon dioxide in the atmosphere. Carbon dioxide is mostly released into the atmosphere via human activities such as the burning of fossil fuels. The danger of climatic change is that as it alters the natural climatic patterns in which the species evolve, they can no longer survive and hence are driven into extinction (Noonan-Mooney & Gibb, 2013). Climatic change can also occur naturally, however, even though natural climatic change also alters life on Earth, it affords ecosystems and species as well as the time to adopt. Unlikely, humanly engineered climatic changes simply speed up the entire process and do not afford such adaptation time (Petronzio, 2015). IUCN (2010) pointed out that climatic change is altering migratory patterns of species and also increasing coral bleaching. Coral reefs provide storm protection, food, jobs, recreation and income for over 500 million people in the world. However, over 70% of the world corals are threatened or destroyed (Harvard T.H. Chan, n.d; University of Michigan, 2006).
Overexploitation, also known as unsustainable use, occurs with the removal of species faster than they are being replaced and when this occurs over the long term, it can result to a loss in biodiversity. Overfishing, which is a good example of overexploitation has led to the exhaustion of the once-plentiful cod fishery in the coast of Newfoundland, Canada (Noonan-Mooney & Gibb, 2013). Petronzio, (2015) indicated that pouching or commercial hunting and other forms of hunting for the purpose of profit making has increased the risk of extinction of predators at the top of food chains. This can result to an unimaginable disaster to the ecosystem (Utz, 2014).
Marine ecosystem bears most of the brunt of over-exploitation (Forster et al., 2011). Bush hunting which provides protein in substantial quantity to lots of people living in rural areas is still taking place at unsustainable level despite lots of measures in various countries to reduce it (CBD, 2010). Overexploitation is primarily done for food, fashion, and profit. Sport or recreational hunting can also cause the endangerment of species especially when it is not well regulated. Illegal poaching remains a major threat to a number of species not only at present but also in the future (Riera et al., 2014; University of Michigan, 2006).
Invasive Alien Species (IAS)
Another interesting cause of biodiversity loss is invasive alien species. These are species which left their natural habitat to new areas and hence threaten biodiversity in their new areas. These species cause harm to the new ecosystem by acting as parasites, predators, and vectors of diseases. Too often than not, these species may not have predators in their new environment and hence their population is not often controlled, and they could grow out of bound (Noonan-Mooney & Gibb, 2013). According to the University of Michigan, (2006), the invasion of non-native (alien) species is often overlooked, but it is a very important cause of extinction. A good example of the effect of invasion of alien species can be found in the African Great Lakes located in Victoria, Malawi, and Tanganyika. The lake was known for its great variety of endemic species that gave it a famous name species flocks of cichlid fishes. However, an introduction of a single exotic species, the Nile Perch has the capability of causing most of the native species to go extinct. Furthermore, hunting accounts for an overall 23% of extinction, habitat destruction 36%, and species introduction accounts for 39% of extinction (University of Michigan, 2006). Interestingly, the invasion of non-native species is primarily engineered by human activities such as climatic change, habitat loss and even scientific studies.
Finally, biodiversity loss can be driven by pollution. Nutrient pollution is one of the most important kinds of pollution driving diversity loss in the marine ecosystem. The nutrients mostly introduced in these ecosystems include nitrogen and phosphorous, and these nutrients could be leached or introduced via eutrophication to the aquatic environment (Carnicer et al., 2015). Leaching and eutrophication are primarily humanly engineered, and the nutrients usually come from fertilizers, sewage and also the erosion of soils containing nutrients. Agriculture, a human activity, is a major backbone of this kind of pollution which drives an immense loss of biodiversity. A good example of the effect of pollution can be found in the several species of desert pupfish which occurs in small isolated pools in the US Southwest (University of Michigan, 2006). Moreover, Acid rain could result from the burning of fossil fuel, and this could drive biodiversity loss for organisms in water and soil (Gao et. al., 2016).
In conclusion, direct drivers or causes of biodiversity loss are all engineered and driven by humans. Although some of these biodiversity loss drivers such as climatic change can be naturally induced but human activities by far exceeds the natural causes in driving these changes. Thus, these drivers of biodiversity loss can be summarized in human activities. Needless to say, human activity is the greatest threat to biodiversity. Although the effect of human activities on biodiversity is well felt in the twenty-first century, it has since been affecting the varieties of life on earth in an untold negative way. Of course, regulatory actions and various measures have been put in place in order to put an end to these gruesome effects on biodiversity, yet more have to be done if we truly want to deal with the problem and conserve biodiversity. Various studies have indicated that with the current trend in biodiversity loss, up to 25% of the species today would have gone extinct in the next century. This is a grievous loss in biodiversity, and thus a lot has to be done in order to deal with it and save the earth. Humans do not only have to think and act towards their own benefits but the benefit and good of the entire ecosystem.
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Appendix: A. overview of factors and threats faced to biodiversity. Source adapted http://www.biodiversitybc.org/assets/Taking~Natures~Pulse/table-23.png