"Over"-Population and Future Un-Sustainability
"Human population growth is the primary environmental challenge we face.." (Cousteau, 1993). Is this a statement valid? The human population has grown at alarming rates in the past century due to vast improvements in average quality of life, and with such a large base it is inevitable that it will continue to grow, even if the rate of growth slows. Increasing population leads to scarcity and contamination and arguably, a decline in average quality of life. However, is overpopulation the real issue? There are many negative effects of population growth, mainly depletion and degradation of resources. According to Thomas Malthus, one of the most famous population theorists, population growth would only lead to natural population controls such as famine and disease. Malthus believed that the main factor controlling population growth was food supply. Despite the validity of Malthus’ worries about the population growing faster than its food supply, there are several other details that need to be taken into account. Many different resources contribute to the sustainability of the population, all of them interrelated. This essay will examine some of these resource restraints on population growth as well as attempt to show that it is not only the size of the population that is the problem. If there were a more equal distribution of resources, instead of great disparities between rich and poor, then the size of the human population would pose less of a challenge than it now does. Regardless of equitable distribution there is however, a limit to which the population could grow and continue to provide for all of its people.
Although Thomas Malthus was not the first to raise the issue of the "population problem", his 1798 essay "An Essay on the Principle of Population" is perhaps the most famous work of its kind. This is not to say that many people agree with him, because there is much debate concerning his theory. Malthus ultimately stated that "the power of the population is indefinitely greater than the power in the earth to produce subsistence for man" (Morris, 1966). He expanded on this by writing that although population grows exponentially, food supplies increase only arithmetically so a growing population will not be able to be sustained by its slower growing food supply. According to Malthus this would lead to "population checks" such as famine and war which were natures ways of controlling overpopulation. Along with these positive population checks Malthus also claimed there were preventative checks such as the deterrent of early marriage (and therefore early and more frequent childbirth) during difficult times. All of these checks were related to limited food supply, Malthusianisms ultimate barrier against population growth. Famine and malnutrition led to increased disease, which would lead to lowered employment which in turn could encourage or discourage marriage. In this sense each of the population checks were mutually reinforcing, although all stemmed from lack of food (Morris, 1966).
Thomas Malthus’ theory is not entirely valid in that he did not acknowledge the limited supply of other essential resources that would arise from the increasing human population. Since he published his essay before the industrial revolution Malthus could not have been expected to predict the massive effects that a larger population would have on the environment and the large scale depletion of necessary resources that would occur. Food supplies are not necessarily the limiting factor on population (and cause of population checks), but instead a combination of the lack of, and unequal distribution of, clean water, air and energy sources that could lead to a worldwide crisis. In a sense, Malthus only discussed one factor of overpopulation and did not account for the future over consumption that is perhaps the real problem.
Over consumption, by the rich minority, may actually a more important issue than that of overpopulation. Over use of critical resources, and degradation of the remaining supplies, has led to these resources being unsustainable at current levels of use. First examining the state of nonrenewable energy sources (principally coal, petroleum and natural gas) it is clear that unless major changes in consumption are made there will be a need for alternate energy sources in the very near future. According to John Harte (1993) even if total consumption levels remained at 1990 levels (a highly unrealistic scenario looking at past trends), new energy sources are necessary to maintain sustainability. A slightly more realistic scenario would be if future per-capita energy consumption remained at 1990 levels with population growth of two percent per year. In this case the three principle nonrenewable energy sources would last only between twenty-nine to eighty-four years (Harte, 1993). Not only are fossil fuel energy sources being depleted, but a growing population also decreases firewood supplies, the primary fuel for a third of humans (Brown et al, 1976). In developing countries, this is often the only affordable source of energy and as the number of people grows there is less space, water and arable soil as well as a greater demand for wood for other needs. All of these factors contribute to deforestation which means less wood fuel available as an energy source.
It is important to examine not only the sustainability of current reserves but also the environmental effects that use of these resources will have. It is however impossible to know all of the environmental effects of anything, since each action has so many reinforcing and far-reaching consequences. In the case of energy sources, fossil fuels, as well as the wood fuel which is often the only affordable option for the poor, cause air pollution which contributes to climate change. This may affect other resources, such as water supply and arable land as a changing climate alters growing seasons and water levels. Deforestation occurs as more and more wood is needed, and as the space taken up by the forests is needed to house growing population and industry. This compounds the problem of global warming since there are less trees to absorb and store carbon dioxide (one greenhouse gas) and transform it into oxygen. Fossil fuel use also contributes to acid deposition which likewise affects water and soil supplies as they acidify and can no longer support life.
Another essential resource that will be, and already has been, greatly affected by a growing population is water. Unlike energy resources water has no substitute. Falkenmark (1986) estimated that the absolute minimum per capita supply required for drinking, sanitiation and other basic personal needs in a moderately developed nation was approximately one thousand meters cubed per year. The average per capita supply will fall below this level when the population is 9.5 times its 1993 size (Harte, 1993). According to Shiklomanov (1993) the global average rate of water withdrawal for human use was 800 metres cubed, while the United States average rate was 2000 metres cubed per year. This is just one example of massive disparities that exist between "developed" countries (especially the United States), and the remainder of the world.
However, water is necessary not only for personal use but also for agriculture and industry (not to mention to support all other life as well). This means that even when the water is not consumed it is still not necessarily available for reuse if it has been contaminated by pesticides, heavy metals and many other pollutants. Although it is possible for humans to improve this degradation the processes are expensive and are often not used. Also water is often not in a closed system so pollution in one area can spread universally through the hydrologic cycle. As discussed above, global warming from human pollutants could contribute to increased water loss from earth to the atmosphere. This is also positively reinforcing since warm air can hold more water and water droplets are one greenhouse gas which in turn cause more warming (Harte, 1993). This is just one effect that depleted water supplies could have. Water loss from soil would decrease crop production and warming lakes and oceans could possibly increase exhaustion of fish stocks.
As developing countries industrialize there will be an even greater conflict between water uses for personal consumption and sanitation and for agriculture versus growing industrial needs. This industrial use will also contribute to and complicate severe biological water pollution problems already existing in these countries that often have few environmental or water sanitation programs in place. Human organic waste has accumulated in the surface water supplies as population increased. This can lead to water-based diseases such as schistosomiasis, a parasitic illness carried by snails that live in irrigation water polluted with human waste. It permanently damages the bladder and liver, leading to a shortened lives, and it is at an epidemic level in many developing countries (Brown et al, 1976).
The third essential resource for a sustainable human population is soil and its use for food production. Approximately 15 million square kilometers were being used for cultivation in 1993 and it is estimated that only about 10 million square kilometers more could be tilled without causing irreversible ecosystem damage. Assuming that crop yields remain constant on this additional land and that the population grows at two percent per year, then only enough food can be produced to feed the human population for approximately twenty-five years (Harte, 1993). However these estimates do not account for soil degradation or erosion. These can be caused by over harvesting the soil which removes essential nutrients, or from decreasing vegetation which would prevent erosion. Pressure from population growth often causes humans to act in ways that increase soil erosion. More people need more wood which leads to deforestation, and more cattle to feed the people causes overgrazing. In this way, as the population grows and requires more food, it is also decreasing the capacity of the soil to provide food so population growth has greater-than-linear effects on its environment (Harte, 1993). Soil erosion, like any environmental problem, also has effects on many other systems than simply crop yield. Eroded soil clogs waterways, reducing the lifetime of reservoirs and increasing the likelihood of floods. Nutrients washed from the soil into surface water can cause eutrophication of these streams and lakes (Harte, 1993). These are merely more examples of the complicated and far reaching effects of any human interaction with the environment.
It is obvious from the above that there is a limit to which current water, energy and soil resources can provide for a growing population. As well as the direct effects that the dwindling of these resources will have the quality and quantity of each of these also plays a role in the amount of food supply available in the future. The three main food systems are; fish from the oceans, animal herds on range lands and farmland used for crops. Each of these systems faces degradation from a multitude of uses, and this is further depleting the ability of each system to provide food for the growing population. As well as the effects of pollution and global warming which may decrease oceanic fish stocks, there is also the direct result of heavy over fishing which caused a crash in most fish stocks in the eighties, resulting in much reduced or non-existent harvests in the early nineties (Brown et al., 1994, p.76). According to the United Nations Food and Agriculture Organization (1991) all seventeen major oceanic fisheries are being fished at or beyond their capacity. The potential of the oceans to feed humans is not only not growing at the same pace as the population, but is declining.
In the same sense, over grazing of range land and over harvesting of crop land contributes to soil erosion and degradation diminishing the capacity of the soil to support these activities. This catch 22 means that, assuming human methods remain the same as past trends, as population grows the land will become more and more over worked decreasing its future sustainability to support further exploitation. Many economies in the South, mainly in Africa and Middle East and Central Asia, depend on livestock to sustain and employ the population. Range lands are, like fisheries, already being grazed at or beyond their limit. This is also true of crop lands, which as they are over harvested, lose essential nutrients through increased erosion, thus decreasing their future capacity to provide crops (Brown et al, 1994).
Thomas Malthus stated that the ultimate limiting factor on human population growth would be limited food supplies. It is possible that this is true although it is a simplification of the real issue. In actuality the three main threats that are threatening humanity are; the rapid increase in world population, the limits to nonrenewable resources and the deterioration of the environment, all of which are inextricably linked and reinforcing (Sauvy, 1975). Another complicating component is the issue of inequitable distribution of the resources that are available. Some theorists insist that adequate food exists to provide for all the worlds people, it is just not distributed properly. Whether this is true or not, it obviously will not remain true with the ongoing rapid population growth and the lack of a corresponding growth in food supplies (Wirick, 1985).
With the current population being as large as it is even if the rate of growth decreases worldwide, as it has in many countries in the South, overall growth will mean large absolute additions. This growth has been a result of improved quality of life leading to decreased infant mortality and increasing life expectancies. Despite these improvements, there has still been a rise in the number of those living in absolute poverty. These improvements have come at the expense of the environment. Advances in "developed" countries have come at the expense of "developing" nations. Countries in the North exploit the lack of environmental laws in the South to attain development without harming their own local environment. Meanwhile citizens of these "poor" countries must also exploit their own resources if they are to merely subsist, let alone "develop" (Ness et al, 1997). This is a huge disparity that must be addressed before any real, global, sustainable development can occur.
Some compromise must be found that promotes the good of both people and the environment. In order to do this new ways of thinking, planning and acting will have to be found that focus on human sustainable use of natural resources instead of simply environmental conservation and emphasize human welfare and responsible parenthood instead of population control (Ness et al., 1997).
Sarah Brimson, 2001
Brown, Lester R., McGrath, Patricia L., and Stokes, Bruce. March 1976. Worldwatch Paper 5: Twenty-two dimensions of the population problem. Worldwatch Institute. Pages 25 & 75.
Brown, Lester R. and Kane, Hal. 1994. Full House: Reassessing the Earth’s Population Carrying Capacity. Starke, Linda (ed.) The Worldwatch Environmental Alert Series. USA: Worldwatch Institute.
Cousteau, Jean-Michel. 1993. Population: Challenge to Biosphere and Behavior. Zuckerman, Ben and Jefferson, David (ed.), Human Population and the Environmental Crisis. California: Jones and Bartlett Publishers, Inc.
Harte, John. 1993. On the sustainability of resource use: population as a dynamic factor. Zuckerman, Ben and Jefferson, David (ed.), Human Population and the Environmental Crisis 1996. California: Jones and Bartlett Publishers, Inc.
Falkenmark, G. 1986. Fresh water-time for a modified approach. Ambio 15(4):192-200.
Morris, Judy K.1966. Professor Malthus and His Essay. Population Bulletin 22 (1). Washington, DC: Population Reference Bureau, Inc. pp7-27
Ness, Gayl D. with Golay, Meghan V. 1997. Population and Strategies for National Sustainable Development: A Guide to Assist National Policy Makers in Linking Population and the Environment in Strategies for Sustainable Development. UK: International Union for Conservation of Nature and Natural Resources.
Sauvy, Alfred. 1975. Zero Growth? New York: Praeger Publishers, Inc.
Shiklomanov, I.A., 1993. World fresh water resources. In:P Gleick (ed.), Water in Crisis: A Guide to the World’s Freshwater Resources. (Oxford, UK: Oxford University Press), pp.13-24
U.N. Food and Agriculture Organization (FAO). 1991. Yearbook of Fishery Statistics: Catches and Landings. Rome.
Wirick, Gregory. 1985. North-South Institute Briefing, World Population: Continuing Challenges. The North-South Institute.
Coral Reefs-a fragile ecosystem
Our Earth is a series of interconnected systems where any action can have far reaching consequences. Political and natural boundaries are not barriers against the spread of problems. Local problems are not isolated and can quickly become global. There has been somewhat more acknowledgment in the past few decades of the necessity to protect certain environmental hotspots (although the actual actions taken have been far from sufficient). In order to effectively deal with environmental issues is it important to fully understand all aspects of the problem. Solutions at both the local and global scale need to be examined. In the case of coral reefs there are many localized direct and more global, indirect causes of degradation. A loss of these major sources of biodiversity (as well as many other important roles such as climate regulation, fishing stocks and coastal protection) could have serious negative consequences. Reefs are fragile ecosystems that need to be protected.
Coral reefs are biogenic reefs that are produced by biological and geological processes. They are composed mainly of corals and coralline algae. Corals are simple, multicellular animals that form a colony of polyps sharing a common gastrovascular system (Hallock, 1997). Corals are composed of two layers: the epidermis that secretes the calcareous external skeleton, and the gastrodermis which is the site where the corals symbiotic algae reside. Symbiosis is a relationship between two species that is mutually beneficial. In this case the corals receive organic carbon, nitrogen and phosphorous from the algae, called zooxanthellae. The algae are autotrophs meaning they can produce their own food (through photosynthesis). They require only inorganic nutrients (which they receive from the corals), carbon dioxide and light. The symbiotic relationship with algae allows corals to survive in nutrient poor waters (Muller-Parker and D’Elia, 1997). According to Mackenzie, 1998, the coralline algae also secrete a hard, calcareous skeleton which helps to cement the coral reef.
Coral reefs have very specific habitat needs. A relatively shallow ocean platform less than 100 metres below sea level is necessary. Water temperatures must be between 18 to 36 degrees Celsius with an optimal range of 26 to 28 degrees Celsius. Most corals exist near their maximum temperature limits meaning they could not survive much increase in sea temperatures. Corals can only exist in levels of average marine salinity, between 3.3 to 3.6 percent. Certain levels of light are necessary for photosynthesis in the algae. Tolerance to UV radiation varies with the species of coral depending on their ability to adapt to different intensities. Corals are somewhat protected by pigment compounds that protect against UV damage. Reefs are also extremely vulnerable to deposition of sediments that may smother or abrade them, shade them from the sun or discourage the settlement of coral larvae. Reefs can also be damaged by the presence of too many nutrients which favours the growth of sponges and algae over the corals (Hubbard, 1997).
Coral reefs are valuable systems with many important uses and roles. The calcium carbonate secreted by corals and their zooxanthellae forms the limestone reefs which store large quantities of carbon dioxide. Without limestones the concentration of carbon dioxide in the Earth’s atmosphere would be approximately 100 times greater. Carbon dioxide is a greenhouse gas that traps outgoing radiation from the Earth contributing to global warming. Such an increase in its atmospheric concentration would make our planet incapable of supporting life (Hallock, 1997). Coral reefs are also significant as the biodiversity "hotspots" of the oceans. Reefs account for 0.2 percent of the total ocean area and 15 percent of the shallow sea floor area of zero to 30 metres in depth (Mackenzie, 1998). Despite their relatively small area coral reefs are home to approximately 25 percent of all marine species and three quarters of all marine fish (Goudie and Viles, 1997). This rich biodiversity gives reef environments great potential as a source for pharmaceuticals and medical treatments. Coastal populations are increasing at an alarming rate and the number of people who depend on coral reefs for part of their livelihood is in the tens of millions. Aside from their large (but vulnerable) fish stocks coral reefs also support many invertebrates and seaweeds that are also used by other marine species and humans as food. Coral limestone is used as a building material as well as for jewelry and souvenirs. They are major areas of tourism aiding the economies of many "developing" countries. Coral reefs are also extremely important as protection for coasts against wave action and storms (Birkeland, 1997). Each of these reasons demonstrate why coral reefs are essential systems with many important features.
Despite all of their beneficial uses coral reefs are being degraded by human beings at an appalling rate. The rapidly growing coastal population has meant increased clear-cutting and development leading to greater run-off and sedimentation. As stated above this can smother or abrade reefs. Increased sediments can also cloud waters blocking the sunlight necessary for photosynthesis in the algae and it can inhibit new coral larvae from adhering to the reef structure. Overfishing and the use of harmful fishing methods such as dynamiting as well as tourism have also greatly disrupted the coral reefs environments. Water pollution from heavy metals has occurred due to mining. Sewage and other pollutants cause accelerated eutrophication (nutrient enrichment) which disrupts the balance between the corals and coralline algae allowing the algae to take over the reef. There are also natural stresses on coral reefs such as hurricanes and El Nino events (Goudie and Viles, 1997). A 2001 study by Caley et al. examined the separate effects of habitat degradation versus habitat fragmentation on species occupying coral reefs around Australia. They discovered that while habitat degradation caused rapid declines in species richness habitat fragmentation had no effect on species richness or abundance. This may be because marine species tend to have greater dispersal capabilities than terrestrial species.
Aside from these more direct strains on coral reefs there are also many indirect global stresses such as climate warming and destruction of the ozone layer. Ozone depletion has lead to increased amounts of ultraviolet light reaching Earth’s surface. While this enables increased photosynthesis in zooxanthellae it may cause UV damage to corals. Although corals contain pigments that offer some protection against UV damage this presents a metabolic (energy) cost to their symbiotic relationship which may surpass the benefits. Global warming will also negatively affect coral reefs as ocean temperatures and levels rise. Since reefs require such a small temperature range and since most exist near their maximum thermal limit even a small increase in ocean temperatures could be hazardous for many coral species. Exposure to a sharp increase in temperatures for a short period of time or to a smaller, more prolonged increase can lead to bleaching (active expulsion of the zooxanthellae by the corals). In severe cases bleaching can cause mass deaths of corals. Extreme levels of oxygen or salinity can also cause bleaching. This is thought to occur because the cost of sustaining the symbiosis is too great. Under conditions of high nutrient levels corals also expel their zooxanthellae but in this case it is necessary to keep the coral from being overgrown by its algae (Muller-Parker and D’Elia, 1997). Coral die offs due to a warming climate will only add to the greenhouse effect (and therefore rising temperatures) from the loss of such a large source of carbon fixation.
Sea level rise from global warming could also adversely affect coral reefs if they are unable to grow at a fast enough rate. Reefs have three growth strategies. "Keep-up" reef growth proceeds at the same rate as sea level rise. "Catch-up" reefs originally start in deeper waters then catch up after the rate of sea level rise slows. "Give-up" reef growth occurs when sea level rises too quickly or if other environmental conditions prevent rapid carbonate secretion. It is likely that most reefs will be able to keep up with current predictions of 4 to 5 millimeter average sea level rise per year (although these are low estimates compared to some). Unhealthy reefs subjected to other stresses (as many are today) may be unable to keep up (Goudie and Viles, 1997).
Yet another cause of recent reef degradation has been the arrival of diseases of the coral such as black band disease and white band disease. These kill the coral tissue leaving behind bands of bare coral skeleton. Although the causes of these diseases are unknown their presence on Caribbean coral reefs has been linked to African sediments blown across the ocean by prevailing winds. Events such as the arrival of black band disease in 1973, mass die-offs of two Caribbean coral species in 1973 and coral bleaching beginning in 1987 occurred during peak dust years in Africa. Clouds of African dust also bring concentrations of nutrients that stimulate algal growth. This will only worsen as deforestation and desertification in Africa increase due to a rapidly growing human population and climate change (www.alternet.org/print.html?StoryID=12619). This is yet another example of how our Earth is a complex, interacting system where every action can have a far-reaching reaction.
Coral reefs are an essential part of marine ecosystems whose influences reach much farther than the oceans. Their degradation by human and natural sources will have many effects at a global and local level. Although public awareness of the need to protect reefs has increased it is not nearly proportional to their value. It is necessary to develop specific, integrated solutions to prevent further damage. These must be applied at the local, individual level since on a larger scale they are almost impossible to implement. However, coral reefs are also affected by other worldwide environmental concerns and until these are addressed reefs will continue to be harmed.
-Sarah Brimson, 2002
Caley, M. Julian, Kathryn A. Buckley and Geoffrey P. Jones. 2001. Separating ecological effects of habitat fragmentation, degradation and loss on coral commensals. Ecology, 82 (12), pp.3435-3448. Ecological Society of America.
Hallock, Pamela. 1997. Reefs and Reef Limestons in Earth History. 1997. Chapman and Hall: USA.
Hubbard, Dennis K. 1997. Reefs as Dynamic Systems. Chapman and Hall: USA.
Mackenzie, Fred.T. 1998. Our Changing Planet: An Introduction to Earth System Science and Global Environmental Change. Prentice Hall Inc.: US.
Muller-Parker, Gisele and Christopher D’Elia. 1997. Interactions Between Corals and Their Symbiotic Algae. Chapman and Hall: USA.
www.alternet.org/print.html?StoryID=12619. Ryan, John C. 2002. Dust in the Wind. Independent Media Institute.