Professor Emeritus of Cornell University David Pimentel remarks, “with the imbalance growing between population numbers and vital life sustaining resources, humans must actively conserve cropland, freshwater, energy, and biological resources…Humans everywhere must understand that rapid population growth damages the Earth’s resources and diminishes human well-being.” The term overpopulation refers to the human population exceeding the maximum population the Earth can sustain indefinitely, given habitat, water, food, and other necessities. It should be noted that overpopulation does not relate to population density or numeric size, but the ratio between humans and available resources. As an environmental issue, overpopulation is associated with topics like agricultural run-off, land use, habitat destruction, fragmentation, climate change, and disease prevalence. In this article, I will explore the last, and in my opinion, most significant issue surrounding overpopulation disease prevalence and transmission. A significant determinant of the quality of human life, disease transmission has affected the ecological relationship between human, microbes, and the environment.
A relatively modern concern, overpopulation was not an acknowledged issue until the late 1880s, and was first addressed by the influential English scholar Thomas Malthus. Originating the idea of carrying capacity, the number of individuals in a given place that can be supported by their environment, Malthus believed the human population would eventually exceed carrying capacity and lead to a global catastrophe. Though not necessarily accurate in all his theories, overpopulation has been the culprit of many of the world’s emerging environmental issues. Having increased since the Bubonic Plague the world’s population reached 1 billion at the onset of the 19th century and as of 2011 has reached a staggering 7 billion people. This exponential growth is a result of an increase in fertility rate following the Ming Dynasty, and WWII, and a decrease in infant mortality due to agricultural and medical innovations. Even with the gradual transition to smaller family sizes, the aforementioned population booms create a sort of unstoppable population momentum that has in many ways exhausted the earth of its resources.
In their article “Ecology of Increasing Disease: Population Growth and Environmental Degradation” David Pimentel et al. assert, overpopulation causes environmental degradation which consequently produces an increase in disease prevalence. Overpopulation is a major cause of urbanization. As of 2007 half of the world’s population lived in urban areas, and it is predicted that by 2025 approximately two thirds of the population will live in an urban environment. These high density areas have intensified the volume of disease and pollution. Examples of this interplay between environmental degradation and infectious disease can be found at sites of water, air, land, or chemical pollution. Environmental changes, like deforestation, have created breeding pools for malaria-transmitting mosquitoes and have subsequently increased the already high prevalence of malaria in Africa. Additionally, vehicle exhaust and industrial fumes have polluted the air in China. This extreme case of air pollution, 300μg/m³, has made respiratory disease the leading cause of death in the country. Also, chemical toxins have been charged with the increased rates of cancer and birth defects in America. Furthermore, areas were land have been cleared has shown an increased amount of helminthes infections, the world total reaching over 2 billion people effected in 2007. All of these cases exemplify the increased stress of environmental degradation.
The increase of Schistosoma mansoni infectious cases in sub-Saharan Africa proves to be the most poignant example of ecological relationship between environmental ruin and disease transmission. J.A.T. Morgan et. Al state in their scholarly article “Schistosoma Mansoni and Biomphalaria: Past History and Future Trends,” that Schistosoma manosoni is one of the most prevalent infectious disease amongst mankind. Associated with fresh water contamination, Schistosoma mansoni provides its host with a chronic illness that damages his/her internal organs. Biomphalaria, a freshwater snail, acts as an obligatory host for the parasites during their larval stage. This parasite has infected more than 200 million people worldwide and has caused approximately 200,000 deaths per year. It is most abundant in Sub-Saharan Africa the location of much of the world’s highest population rates. The preferred colonization site of Biomphalaria, the parasite is popular around large water development projects. Consequently these areas are also the location of highly populated towns and villages. The result is high disease prevalence. An example presented in “Schistosoma Mansoni and Biomphalaria: Past History and Future Trends” is a 1985 Senegal damn. A large 40 km barrage was constructed to increase irrigation and decrease salinity. However, it also provided comfortable breeding grounds for the Biomphalaria. Uninfected before 1988, as of 1994 approximately 72% of the surrounding population was infected. Moreover, the Senegalese basin is now the most Schistosoma Mansoni infected area in the world.
Laurie Garret discusses how overpopulation has affected the ecological relationship between humans and microbes in her article, “The Return of Infectious Disease.” As aforementioned, overpopulation is the major reason for urbanization. Comparably population growth also caused a globalized society. The combination of these two factors has caused the mutation of microbes. The microbes that contain RNA and DNA codes mutate when stressed. These mutations allow the aforementioned microbes to search for useful genetic materials like transposons and plasmids. “Some plasmids carry genes for resistance to five or more different families of antibiotics, or dozens of individual drugs. Other confer greater powers of infectivity, virulence, resistance to disinfectants or chlorine, even such subtly important characteristics as the ability to tolerate higher temperatures or more acidic conditions” (Garrett, L. 1996). As a result of these mutations researchers are currently having trouble making new and effective antibiotics. Furthermore, these diseases are being carried around the world due to the global market, thus “human mobility affords microbes greatly increased opportunities for movement” (Garrett, L. 1996). For example, “even before commercial air travel, swine flu in 1918-19 managed to circumnavigate the planet five time in 18 months killing 22 million people, 500,000 in the United States” (Garrett, L. 1996). So you can imagine the possibility for microbe transmission now? Statistics states that population growth should increase disease prevalence. However overpopulation, mutated microbes, and globalization complied with, “these new centers of urbanization typically lack sewage systems, paved roads, housing, safe drinking water, medical facilities, and schools adequate to serve even the most affluent residents. They are squalid sites of destitution …so jammed together as to ensure astronomical transmission rates for airborne, waterborne, sexually transmitted, and contact-transmission microbes” (Garrett 1996) prove create a major public health hazard.
The 2003 outbreak of SARS acts as a perfect example of this newfound microbial-human relationship. The SARS (severe acute respiratory syndrome) outbreak began in Hong Kong in November of 2002 and spread worldwide claiming over 900 lives by July of 2003. People from areas like Canada, the United States, Taiwan, and Chinese farmland made up the over 900 people who died of SARS. Unlike epidemics from earlier centuries SARS affected people on opposite sides of the globe at an accelerated rate, less than one year (Ali, S.H 2006). “Global Cities” like Toronto, New York, and Hong Kong were the breeding grounds of the pathogen (Ali, S.H 2006). SARS moved through regions of the world the microbe could not have managed without the increase of travel. Therefore, with the rate of air travel on the rise, due to the world growing global economy, human mobility has affected the ecological relationship between humans and microbes.
“A comprehensive, fair population-limiting policy combined with an effective environmental management program is essential” (Pimentel 2007). There have been a plethora of proposed solutions to overpopulation and disease prevalence transmission. However, few if any proposed solutions will significantly decrease population or decrease it ethically.
Thomas Malthus proposed a rather controversial solution to overpopulation. The English philosopher believed that population growth would create food scarcity and a labor surplus. These factors would subsequently cause an increase in food prices and a decrease in wages. These factors would force the now impoverished working class to starve and decrease reproduction and thusly create population stagnation. He famously remarked “premature death must in some shape visit the human race.” He also pointed to famine, natural disasters, disease, war, infanticide, and murder as positive checks to a growing population. Amongst its many ethical issues, Malthus’ solution implies a functional role of social inequality and catastrophes like death and violence. It also ignores the possibility of technology in improving society’s ability to produce antibiotics and drugs.
Most recently there has been a demographic transition that shows signs of decreasing population growth. Families are now having fewer children so as to allot more resources to the each child. The problem, however, with this solution is that it is most common in developed countries, while major population growth is taking place in developing countries. Thus the countries with the largest population are steadily having more and more children. Additionally, it would be unethical to force this demographic transition on anyone. However, some point out that female education and available contraception would enable this demographic transition. This, however, would only by plausible if the males of these third world countries would support female education and consequently female empowerment. Considering the social states of certain Sub-Saharan African continent, this seems an unrealistic solution.
In his article, Richard William Ashford “Disease as a Stabilizing Factor in the Protection of Landscape: The Leishmaniases as Models” asserts that disease prevalence and transmission is not a problem of overpopulation but can instead be the solution to overpopulation. “It is inconceivable that any self-regulatory mechanism will bring human populations down to a level compatible with the survival of other…so they only hope for environmental survival is disease” (Ashford 2007). The article asserts that disease limits populations, however only under exceptional circumstances. Due to technological and agricultural innovation humanity has increased carrying capacity. Ashford asserts that these advances have lead some people to believe that the Earth has no carrying capacity. However, this kind of thinking proves to be a result of lethal myopia. After all, there are many researchers that believe population has already surpassed the planets carrying capacity. Ashford argues that Leishmaniases is the most likely disease to defend the planet against overpopulation. The Leishmania parasite is transmitted by a variety of region-specific sand flies. It produces skin ulcers and can develop into a dermatosis resembling leprosy. In its most lethal incarnation, Leishmania will spread to its host’s internal organs and cause deadly ulcers. Interestingly, strains of Leishmania only appear when the environment is being anthropogenically degraded and disappears when the threat dissipates. Examples include the disfigurement of bandits destroying Kenyan forests, and gold-diggers damaging the Amazon. Ashford concludes remarking, “Whether it is a parasite or other disease that eventually halts the inexorable increase of the human population, once conditions are right for its spread (they probably already are), we will have to wait till it comes. And during the waiting period, populations will continue to grow: the world will be (most would say already is) in a kind of ‘supersaturated’ state. So the disease, when it arrives, will not only halt further growth, but will bring the population back down to, or even well below equilibrium level.”
With the present solutions either unethical or almost science fictional in nature society must ask itself an even more important question: “Is the problem really overpopulation?” What proof is there that this is a problem and not simply an interesting correlation? The world has experienced environmental changes before, so why is this specific case so associated with overpopulation? What additional proofs can be examined to prove that overpopulation and environmental change are not only correlated but causal? Is this even a possible experiment, does just looking at natural history successfully prove the point? All of these questions have no real answer, but instead point more poignantly at the over –consumption argument. Most recently research has divided the ecological community into two factions concerning negative anthropogenic effects on the earth. The argument questions whether overpopulation is really the problem or is overconsumption by industrialized first world counties really to blame. Therefore is the issue not the raw ratio of humans to available resources, but the levels at which people are accessing and/or wasting these already scarce resources?
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