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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?


Alexander, A. (2008) The Ecology of Overpopulation and Overconsumption. Web.


Ali, S.H. and Keil R. (2006) Global Cities and the Spread of Infectious Disease: The Case of Severe Acute Respiratory Syndrome (SARS) in Toronto, Canada. Urban Studies Vol. 43. 3, 491-509. Web.


Ashford, R. W. (2007) Disease as a Stabilizing Factor in the Protection of Landscape: The Leishmaniases as Models. EcoHealth. Vol. 4. 99-103. Web.

Garrett, L. (1996) The Return of Infectious Disease. Foreign Affairs Vol. 75. 1, 66-79. Web.


Holdren, J.P. and Ehrlich P.R. (1974) Human Population and the Global Environment: Population growth, rising per capita material consumption, and disruptive technologies have made civilization a global ecological force. American Scientist Vol. 62. 3, 282-292. Web.


Morgan, J.A.T. et al. (2001) Schistosoma Mansoni and Biomphalaria: Past History and Future Trends. Parasitology Vol. 123, 211-228. Web.


Pimentel, D et al. (2007) Ecology of Increasing Disease: Population Growth and Environmental Degradation. Human Ecology Vol. 35, 653-668. Web.


Shah, A. (2001) Human Population. Web.


Shah, A. (2001) Stress on the Environment, Society and Resources? Web.


Shah. A. (2001) Effects of Over-Consumption and Increasing Populations. Web.




3 Responses to “Overpopulation: Disease Prevalence”

  1. Sarah says:

    The topic of increased instances and severity of pathogens is a great topic! That being said, I was at times a little confused as to the ecological aspect of this issue. I understand that the degradation of our resources and landscapes can create conditions that foster the growth and reproduction of pathogens, but you also discussed overpopulation and globalization. I completely agree that all three of these potential causes are important, and are themselves interconnected, but I was looking for direct discussion about how they impact the increased prevalence of pathogens and instances of disease. The example you discussed near the end of the paper, Leishmaniases, was really interesting to me. The way that it has higher infection rates, as rates of ecosystem degradation increase is fascinating! Perhaps, some more in depth discussion of the ecology behind this interaction between the reproduction and growth rate of the pathogen, and anthropogenic actions could help to really drive home the connections you are making throughout the paper.
    The issue of overpopulation, and exceeding our carrying capacity is very important. However, it seemed as though this was more of a complimentary topic to your discussion of pathogens, as opposed to the environmental issue you were spotlighting. There is a lot of good information in your article, but I think the progression of thought could be a little stronger, with some more structured organization. I found myself going back and forth as to what was the environmental issue that you wanted to focus on-environmental degradation? I think you want to talk about a lot of different aspects to increased pathogen presence in this piece-globalization, overpopulation, and degradation, but maybe it would be more powerful to focus on just one or two, and discuss their relationship with pathogen prevalence, and the importance of the issues.
    I felt that your examples of pathogenic outbreaks at times were a little unfinished. Instances, like the outbreak of SARS, and the increased habitat for Malaria carrying Mosquitoes are really important and very connected to various environmental issues, however others, like helminthes infections, and biomphalaria left me wanting more information. I don’t actually know what helminthes infections are, or how one gets one, or where. In terms of biomphalaria, I was really intrigued by the story of the 40 kilometer barrage, but I wanted to know more about the ecological changes that resulted from its construction, and how those changes influenced the huge increase in instances of infection.
    In terms of style, I felt at times as though the sentence structure was quite jumpy, resulting in me reading the lines a couple of times to understand the transitions you were making in topics. I also picked up on a few grammatical errors (the bolded word is either incorrect, or wasn’t there):
    -”…..areas where land have been….”
    -”…most poignant example of the ecological relationship between…”
    -”…..dozens of individual drugs. Other confer greater powers….”
    -”…certain Sub-Saharan African continent…” (should be “countries”?)

    Your strengths in writing are definitely your passion, and strong, authoritative tone. Throughout the piece I could tell that you feel very strongly about the increase in pathogens and transmission. You also used very strong language, identifying characters in the scenarios you described, and staying away from the passive voice. I think maybe in your excitement about the topic, you just didn’t realize that there were a few typos, which happens to everyone. With a read through or two before posting, you would be fine on that front. I think there is some room for improvement on sentence structure and fluidity of your arguments, as I talked about earlier. There were some fragmented sentences, as well as some times when it seemed as though the way you had structured a sentence did not portray in information as you had intended. I would also be careful of putting the wrong emphasis on sentences. The one example that stuck out to me was:
    “..thus the countries with the largest population are steadily increasing.”
    Are you saying that the rate of children per family is increasing in those countries, or that the overall populations of the countries are steadily increasing?

    Overall, there is a lot of great information in this piece. With a little reorganization and editing, your strong tone and passion for the topic will bring out true importance of these issues. A great first draft!

  2. acp86@cornell.edu says:

    This was an interesting topic to read about! You certainly conveyed the importance of the environmental issue in this blog. I knew that over-population was a problem, but had never looked into the ecological reasons why before now. As you said, now that people are traveling more and introducing new diseases as they travel, disease transmission will become a more dangerous act. I would suggest, however, making more direct and overt connections between the ecology and the environmentalism when making your arguments. For example, when you talk about Schistosoma mansoni, the paragraph ends rather abruptly without rounding out the ecology behind the argument. You’re blog does flow logically, however, from one point to the next, and I really liked the conclusion. Introducing all of those questions demonstrates just how much work still needs to be done on this topic, but you still closed the blog nicely. I think you could expand upon your quotations, however. Sometimes you use a quote to support a previous argument, which is good, but I am not sure that you can just move on to another point without explaining it a bit. Overall, I think this was a job well done!

  3. er382@cornell.edu says:

    I definitely agree with both of you (above). I thought I was aware of the dangers of overpopulation but you really shined a new light upon the subject and allowed us to view the issue at a more ecological/environmental angle. Nonetheless, I really did enjoy the topic, its flow, and its organization. However, like acp86, I also agree that you should just state the connections directly instead of how it was done. But other than that, it was a great read :D.

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