Overpopulation occurs when the population of certain region exceeds the carrying capacity of that region in terms of the resources required to sustain the population. From a global perspective, human overpopulation is a serious issue and is on the rise mainly due to high birth rates, especially in developing countries, and falling death rates due to improvements in health care. Overpopulation is a major component of the tragedy of the commons in that more people are sharing the same resources which means less per individual. The scarcity and competition over resources results in overexploitation, and this has severe environmental consequences such as deforestation, soil erosion, pollution and loss of biodiversity to name a few.
As population increases, more space is required for human settlements and this results in urbanization. Urban centers tend to be the focal point of economic activity and therefore many people migrate to big cities. As the urban centers get overcrowded, hygiene and sanitation standards fall as disease and epidemics can spread rapidly. Urban centers therefore grow in size to meet the required population capacity and continually push back the rural urban fringe, which is the boundary between urban and rural areas. To develop urban areas, large amounts of land must be cleared and excavated to construct infrastructure such as roads, bridges, buildings etc. Very often, the clearance of land requires deforestation and this leads to fewer trees holding the soil together. The soil becomes loose and easily erodes due to the erosive agents of wind and rainfall. Hengeveld writes of how mountain forests were cleared such that the trees could no longer protect the forest floor against erosion and rain water ran off with ever-greater force, first removing the humus and then the mineral soil and stone (Wasted World, 160). Soil degradation is a major consequence of deforestation and loss of soil fertility adversely affects the agricultural potential of the land and therefore food production. Hengeveld discusses the effects of overpopulation and its influence on deforestation when he writes how “population growth results in vast deforestation as our demand for agricultural land and wood for timber for all aspects of urbanization are still increasing, and our tools for cutting down trees are becoming ever-more efficient and powerful” (Wasted World, 162). Loss of forested areas also means destruction of natural habitats, and this threatens biodiversity. Certain species are well adapted to the forest habitat and are unable to survive in alternate ecosystems. Deforestation has been linked to the endangerment or extinction of many species and the IUCN reports that worldwide, 12 percent of mammals, 12 percent of birds, 31 percent of reptiles, 30 percent of amphibians, and 37 percent of fish are threatened with extinction (Red List, 2009). Deforestation in specific locations have holistic effects as they influence the hydrological cycle in terms of evapotranspiration, interception of rainfall and surface runoff and Hengeveld discusses this when he writes how “cutting down large stretches of forest also affects continental patterns of cloud formation and therefore of temperature and rainfall, which are impossible to reconstitute (Wasted World, 159). The expansion of settlements also requires large amounts of raw materials which are generally extracted through mining. For example, limestone must be extracted to produce the concrete required for infrastructure. Mining activities may result in deforestation as well as the excavation and scarring of land either due to open pit or underground mining. The growth in population is also accompanied by an increase in the amount of waste produced by human activities. Large amounts of waste are especially produced by the primary and secondary sector of an economy as Hengeveld writes, “all kinds of chemical waste discharged by laboratories, factories, gardening centers, and horticultural industries pollute large tracts of land and end up in the groundwater, creeks and rivers” (Wasted World, 178). The amount of waste produced has dramatically increased which can be observed from the fact that islands of waste, such as the Great Pacific Garbage Patch, are forming in the oceans and are causing serious harm to marine life and the coral reefs. Overpopulation has resulted in the growth of urban settlements which in turn increases deforestation, land degradation, waste and pollution.
Overpopulation is accompanied by growing demands for food and fresh water. Limited amounts of resources relative to the population size drives the prices of resources such as crops up and this acts as a positive feedback loop which encourages greater exploitation of resources for profit. Increased demand for food leads to greater amounts of agriculture and livestock farming. According to Pimm, “Forty percent of the planet’s land is devoted to human food production, up from 7 percent in 1700” (The World According to Pimm). Consequently, land must be cleared and cultivated which may result in deforestation and soil erosion. As farmers try to maximize yields, the soil may be overused leading to soil exhaustion and loss of soil fertility. Overgrazing is another serious issue as the number of livestock increases to meet growing demand. Soil may become barren and this may lead to desertification if the region is relatively arid or semi-arid. For example, the Sahara Desert in Africa has been expanding at alarming rates and human activities have played a major role in its growth. Farmers also use fertilizers and other chemicals to maximize crop yields, and these chemicals kill many important plant and animal species causing an imbalance in the natural ecosystem. Chemicals also leach into the soil and eventually enter water bodies, a process known as eutrophication. Eutrophication encourages rapid growth of aquatic plants and algae which consume large amounts of oxygen in water bodies and cause a decline in other animal species in that habitat. Overpopulation also leads to overfishing in much the same way as it leads to intensive agriculture. Fishermen are encouraged by growing profits and demand for fish and therefore overexploit fish populations. The collapse of the Cod fishery in Newfoundland Canada is a well-known example of how unsustainable practices influenced by overpopulation can result in the decline or extinction of certain species. Water is a necessity of life and is essential in almost all aspects of human activities. Only about 0.003 percent of the water on earth can be consumed as clean water, and this figure is likely to decrease. Large quantities of water are used for irrigation and as raw materials in industries. The increased use of fresh water and other human activities have greatly affected fresh water ecosystems. The increased number of dams, settlements, and overfishing have caused a huge strain on the already fragile freshwater ecosystems. Hengeveld writes that “Because of the need for water for irrigating the land and also for supplying towns and industries with water, groundwater levels all over the world are dropping” (Wasted World, 130). The increased use of water has caused many water bodies to decrease in size or completely dry out. Hengeveld notes how the Colorado River no longer reaches the ocean, and the Mississippi is likely to follow a similar trend (131). The development of coastal settlements and land clearance for agriculture has also greatly affected the mangrove forests. These areas are crucial as they serve as nurseries and breeding grounds for many aquatic species such as fish and shrimp. More than one in six species of mangroves are endangered due to coastal development and other human activities (Red List, IUCN). Overpopulation has resulted in the increased exploitation of resources to provide food and water to the growing population, and this in turn has resulted in soil degradation, water pollution, species endangerment and a growing shortage of fresh water sources.
Overpopulation is a very critical issue, as a growing number of people means more food and space is required, and resources are limited. To meet increasing demands, we are forced to exploit resources to the extent that they may not be replenished. Furthermore, the processes by which we seek to sustain the growing population are associated with severe environmental consequences such as deforestation, soil degradation, pollution and a loss of biodiversity.
Hengeveld, Rob. Wasted World: How Our Consumption Challenges the Planet. Chicago: U of Chicago, 2012. Print.
International Union for the Conservation of Nature. 2009. Red List.
Pimm, S. L. 2001. The World According to Pimm: a Scientist Audits the Earth. McGraw-Hill, NY