World system theories define inter-regional, transnational, and national division of labor that split the world into core, semi-periphery, and periphery countries. The primary focus of core countries is high skill- and capital-intensive production, while periphery countries’ focus is on low-skill and labor-intensive production, and raw material extraction. Consequently, core countries dominate the world. However, technological revolution can change the status of a country from periphery to core country. Periphery countries comprise developing countries, while core countries comprise developed countries. Examples of core countries are the United States, the United Kingdom, Germany, Netherlands, France, Israel, Japan, and most of West Europe. Periphery countries include, but are not limited to, African countries excepting South Africa, India, Latin America excepting Brazil and Mexico that are semi peripheries, and most Middle East countries.
The dependency theory relates to the argument that core countries exploit periphery countries, i.e., third world nations, to enrich themselves, while the latter remain poorer and often, powerless. Proponents of this theory contented that resources originate from periphery or underdeveloped nations and end up in the core or developed countries, enriching the latter at the expense of the former (Norton & Mercier, 2016). As a result, periphery nations continue to depend on core nations. 3
- Population Density
Population density denotes the degree of population distribution or clusters in a particular area, country, region, or the world (Malpezzi, 2013). It is the total number of people living in a unit area. In some situation, the density can be even, while in others, it can be uneven. For instance, Canada’s population density is unevenly distributed; cities have high population density, while larger areas have low density. The 2014 single statistics produced a population density of 3.5 people per square km. despite a combination of large unpopulated and relatively small-populated areas (Norton & Mercier, 2016). Nonetheless, one can infer that population density refers to how number of people living in a particular place, or, in other words, how populated an area is. 3
- S-shaped Curve
An S-shaped curve occurs when the process of growth starts slowly, then increases rapidly or exponentially, and then levels up at the peak. In other words, before high population density in an area is achieved, the population starts growing at a low momentum but in a positive acceleration during the early phases, after which it reached a climax/top-speed growth rate that is rapid. After the rapid increase, the growth reduces in a negative acceleration to a level where the population achieves stability or equilibrium and stabilizes with no more growth. 3
- Malthusian Theory
The Malthusian theory is premised on the idea that humanity needs food for its continued existence. Similarly, sexual intercourse between opposite sexes is a necessity for the continuation of the species. However, the rate of population growth is higher than the rate of food production. Consequently, according to Malthus, population will rise to reach a point where it will surpass resource growth, such as food production or availability, putting stress on the means of subsistence. Nevertheless, in theory, if human rationality is something to go by, methods such as family planning and moral restraints such as deliberately delayed marriages and singlehood can be adopted, reducing fertility rates, which might end up correcting the population-food imbalance. On the contrary, people cannot voluntarily use such methods, and hence natural forces such as war, famine, flood, and disease continue to keep human population at a manageable level. The theory warned humanity of the likelihood of an impending catastrophe owing to unchecked population growth. For example, the world wars II and II started because nations could not solve their conflicts over resources. He did not anticipate the dramatic increase in food production. 2
A refugee is a foreign national forced to leave own country because of being affected by war, persecution by the state, or natural disaster. A person is considered a refugee when they unwillingly leave their home country to seek safe haven elsewhere because the situation in their home country makes life untenable. Therefore, such people go to stay in another country as they wait for normalcy to return to their country of origin. Syrians leaving their homes in Syria to seek safety in Europe and Turkey are refugees. 3
Population growth models play an important role in explaining various population dynamics affecting different species or organisms (Mateo, Arroyo, & Garcia, 2016). Similarly, they help in research to create a correlation with decrease or increase in population and its impact on the environment. Such models facilitate the understanding of complex processes and interactions in nature. In this regard, modeling in nature provides manageable mechanisms for scientists to understand changes in the population size in a given time period and to make sense of these changes. Therefore, population modeling is used a tool for identifying certain patterns related to population change (Hastings, 2013). For instance, it is possible to study the impact of population increase or decrease on the environment. Similarly, through modeling, patterns will emerge showing the effects that a change in the population of one species has on other species as well as intra-species implications. Hastings (2013) explains how modeling of human population improved the understanding of demography, which tells about a country’s population composition, resource use, population growth rate, population density and distribution, as well as age and life expectancy. Additionally, demographics are vital in policymaking, national planning and resource allocation. This vitality explains the value of population modeling. Creating an appropriate population model is expected to improve the understanding of the factors that drive population growth, and scientists gain knowledge concerning resource usage and consequence of population growth on the environment.
There are five primary models explaining population growth and its effects on natural resources. These models are the S-shaped Curve, Malthusian theory, Marxist theory, Boserup theory, and the Demographic transition. The S-shaped curve model explains that when an area’s population density starts increasing, it begins slowly in a positive acceleration manner, followed by rapid growth so that it reaches exponential growth rate before leveling up to a point of equilibrium, that is, zero growth rate (Tobin & Dusheck, 2005; Forman, 1997). The zero growth rate is also known as the carrying capacity. The negative acceleration comes into play because environmental resistance increases in times of high population density. For this model to be effective, it is produced under controlled experimental conditions. However, Norton and Mercier (2016) contend that even though population growth may begin slow and then acquire momentum, it is normal for plant and animal population to remain steady at the top. Sometimes, the final stage of growth can involve some oscillations. Even as the S-shaped curve can predict growth, it fails to take into account external factors such as economic and cultural factors. For instance, in view of fertility issues, the human decision to control birth rates willfully can affect population stability, while natural law cannot do so.
Mishra (1995) and Yamaguchi (2014) explain that according to Malthusian theory, human population growth happens at geometrical progression, and would therefore outstrip human capabilities of food production as this increases arithmetically. As a result, the land resource, which is the source of food, directly restricts population growth, density, and size. When population outruns subsistence resources such as food, the imbalance is corrected by preventive checks comprising moral restraints such as delayed marriage, family planning, and celibacy (Van Bavel, 2013). However, Norton and Mercier (2016) explain that since people are unable to use such methods, positive checks like famine, natural disasters such as floods and drought, war, and disease increase mortality rates, and work to reduce population. Consequently, human population is reduced to environmentally sustainable levels. The underlying assumption is that natural resources such as land are fixed, making it hard to increase food production. The theory’s shortfall lies in focusing on food production technologies alone, while ignoring the effects of technological changes and their effects on the environment. Moreover, Malthusian theory does not discuss the consequence of population change on the environment or food production technologies.