The relationship between population growth and the environment is one that has long been debated. In her paper “Four Theories of Population Change and the Environment” (1994), Carole L. Jolly, of the National Research Council, evaluates theories exploring this relationship. In her review she divides previous work regarding the connection between population growth and environmental degradation into four main theoretical frameworks in which population growth plays a distinct and different role. Neoclassical economists view population growth as a neutral factor having no intrinsic effect on the environment; classical economists and natural scientists see high population growth as casing environmental degradation by acting as the independent variable; dependency theorists argue that high population growth is linked to environmental degradation in that both are caused by poverty; finally some analysts see population as a proximate determinant where high population growth strengthens the effects of environmental degradation but is not the ultimate cause of it (Jolly, 1994).
Neoclassical economists are primarily concerned with the ability of the economy to maintain or improve standards of living. In the case of populations growth, neoclassicists argue that well-functioning markets can keep up with population growth. While natural resources may be depleted due to population growth, neoclassical economic theory maintain that manmade substitutes for these resources will be found and therefore living standards will be maintained. All of these arguments rest on the stipulation that markets respond effectively to scarcities of natural resources. In practice, this is often not the case, and therefore population growth may intensify market inefficiencies (Jolly, 1994).
Neoclassical economists, lead by Julian Simon, argue that despite this, in the long run population growth stimulates an economy by increasing the number of consumers. This increases demand which in turn causes economic expansion and research and development to meet demand. This total chain effect causes living standards to increase. Thus Simon argues that while population growth may cause degradation and depletion of natural resources, there are also more bright people which increases the likelihood that technological advances will be made allowing substitutes for those natural resources to be in place (Jolly, 1994).
To demonstrate this principle, Parker Shipton (1989) studied densely populated areas south of the Sahara. He found that as population density increased, output increased due to innovations and conservation measures. Shipton argues that environmental impact is greatest in middle density populations as demonstrated by evidence from Kenya where land deterioration is high but population densities are neither high nor low (Jolly, 1994).
While classical economists are also concerned with an economies capability to maintain or increase standards of living in the face of population growth, they argue that sustainable output and rapid population growth are not compatible. Thomas Malthus first presented this framework for population growth when he proposed that while population grows geometrically, food supplies increase in a linear fashion. Thus, population growth would eventually exceed food supply and living standards would decrease. Richard Hosier (1984) supports this claim with his study of land degradation in Kenya. He was able to show a correlation between high population density on high-potential lands and low wood availability (Jolly, 1994).
Natural scientists approach the connection between population growth and environmental impacts similarly using the concept of carrying capacity. They emphasize the finite nature of natural resources; thus all individuals have a negative impact on the environment as they use up resources. Carrying capacity refers to the point at which a population is too large to be supported by the fixed resource base (Jolly, 1994).
Lester Brown et al. in State of the World (1987) argue that much environmental degradation in developing countries is a result of high population growth rates due to the fact that these countries are in the middle stage of demographic transition where birth rates are high and death rates are low. Brown claims that if populations continue to grow, environmental degradation and poverty will continue to be issues in developing nations (Jolly, 1994).
Unlike neoclassical and classical economists, dependency theorists are not primarily concerned with living standards; rather their main focus is on the structure of a society, and they see environmental degradation as a result of societal relations and changes in production systems. One perspective that has come from dependency theory is that while population growth and environmental degradation are linked, they are not causally linked. These dependency theorists maintain that population growth and environmental degradation are both the result of poverty and that the structure of a society causes these symptoms (Jolly, 1994)
Like dependency theorists, regional political ecology focuses on society’s structure examining the ecological and social factors leading to environmental degradation. In this context, population growth is not the independent variable causing environmental degradation, but is simply one of many variables affecting natural resource depletion. Demonstrating this theory, Susan Stonich (1989) analyzed land degradation in southern Honduras. She found that a high population growth rate of 3.4% from 1974 to 1985 exacerbated land degradation by causing limited resources to be allocated to an even larger number of farmers. The initial problem was not population growth, but the manner in which capitalist agriculture was introduced; prime land resources became concentrated in the capitalist sector while marginal lands were left to farmers outside the modern sector. These farmers were forced to overexploit land resources to meet subsistence needs of people. The high population growth rate during the period worsened an already poor situation (Jolly, 1994).
The fourth framework in which to analyze the relation between population growth and environmental degradation is formed by theorists who argue that the root causes of land degradation are exacerbated in the face of high population growth. These root causes vary from region to region. Because of this relationship, R. Paul Shaw (1989a) claims that neoclassical and classical theories can be reconciled. This is because population growth is not the fundamental cause of land degradation. Though it does intensify the effects of the root causes (Jolly, 1994). For example, Robert Repetto (1989) studied the causes of soil erosion in Java. He found that low employment opportunities forced people to turn to turn to agricultural practices. When they began to cultivate ecologically fragile lands, they did so with poor agricultural practices because Java’s agricultural policies do not provide rural credit to allow appropriate technologies to be used. Population growth intensify both fundamental causes by increasing demand for agricultural productivity that lead to increased environmental degradation (Jolly, 1994).
It is clear that all four frameworks for analyzing the relationship between population growth and environmental degradation have strengths and limitations. The neoclassical economic theory, in a market economy under efficient conditions, explains resource allocation and shows that land degradation is the result of price distortions or other market failures. It is limited in that is does not distinguish between scale and allocation and relies heavily on substitution elasticity. Additionally, distorted prices are difficult to identify. Neoclassical economists also disregard the importance of population growth rates in determining standards of living. Lastly, the neoclassical economic framework does not incorporate institutional factors affecting resource use (Jolly, 1994).
The classical economic and natural science perspective allows scale to be addressed. However, the calculation of carrying capacities tends to overlook the contribution of the industrial sector and technological innovation and thus provides inaccurate analyses (Jolly 1994).
The dependency and political regional ecology theorists have the strength of seeking out the root cause of population growth and environmental degradation as opposed to attempting to find a causal relationship between the two. In addition, this framework addresses distribution issues. It is limited in that dependency analysts tend to look solely at a societies structure based on the relationship between developed and developing countries. In addition, they discredit the concept of carrying capacity which is useful analyzing the degree of land degradation. Lastly, this framework is weakened in that poverty and fertility are not uniformly related (Jolly, 1994).
Theorists that approach the relation between population growth and land degradation by seeing population growth as an intermediate variable have the advantage of allowing for a method to analyze how population changes affect the environment in different situations. They are limited in that a focus on the effect of population growth over the root variables allows political attention to be diverted from addressing the true underlying factors causing land degradation. In addition, the theory does not offer much in the way of explaining these root causes (Jolly, 1994).
It is clear that in each of these four theories population growth plays a different role. High population growth is neutral for neoclassical economists; it is the independent factor causing land degradation for classical economists and natural scientists; it is a symptom of poverty for some dependency theorists; and for analysts that view population as a proximate determinate, high population growth is an exacerbating factor. Unfortunately, with no time series data available, additional quantitative empirical research is needed for all four theories. There is clearly no consensus on the relationship between population growth and land use at present. The policy implication here is that policies stressing family planning and other methods of decreasing population growth rates may not necessarily have a positive influence on environmental issues (Jolly, 1994).
In his article “Population and the Environment: The Scientific Evidence” (1994), Samuel H. Preston argues that poor research design causes analyses of the relation between population growth and environmental impacts (particularly pollution) to be inadequate. Preston argues that population growth has, and is, contributing to environmental changes, though not all of these changes are negative. He claims that an increase in population causes an increased need for food that in turn increases the amount of resources used for food production; this ultimately leads to a decrease in resources in their natural state. The evidence for this relationship is found in the pattern of land use change over time which shows a clear association between population growth and a loss of forest as well as an association over space (Preston, 1994).
In addition to causing intensification of agriculture on already occupied lands or extensification to new lands, population growth leads to increased production and consumption of other goods and services (Preston, 1994). This has environmental implications which have been modeled using the I = PAT equation where I = environmental impact; P = population size; A = affluence (usually measured by GNP per capita); and T = technology (usually measured as pollution per unit of GNP) (Preston, 1996). Preston points out that this equation ignores interactions among variables and causes the contribution of population growth to always be equal to the proportionate change in population (Preston, Year).
Preston also emphasizes that one must look at the relationship between population growth and environmental impacts not only on a biological level but on a social level because human beings have a high propensity to be innovative and mitigate such impacts. Through the impact of social institutions that govern ownership and access to natural resources, environmental degradation is not a necessary outcome of population growth. Michael Mortimore (1993) demonstrated this in his analysis of environmental change in northern Nigeria. He found no evidence of soil deterioration during the period from 1977 to 1990 in a densely settled agrarian zone of rapid population growth. He concluded that sustainable resource management by smallholders was compatible with high population density and population growth (Preston, 1994).
Preston also notes the role of social institutions in affecting the effect of population growth on the environmental by comparing forest resources in China and Japan. This same comparison is made in his article “The effect of population growth on environmental quality” (1996). He points out that the weak administrative structure in China resulted in peasants clearing tracts of forests to pursue short-term solutions to population pressure. Conversely, in Japan when increased demands for timber were felt, the imperial government of the 17th century limited extensive forest clearing. Thus, while much of China is now deforested, much of Japan’s land has been protected (Preston, 1996).
In this article, Preston again addresses the shortcomings of using I = PAT in analyses. He show that even by expressing the variables as growth rates, the formula misses spatial distribution and interactions between population growth rates and per capita GNP as well as between per capita GNP and technology. However, by expressing the variables in terms of variance, one gets results that are more compatible with what is observed when studying environmental impacts. When one uses this new formula to examine carbon dioxide emissions from 1980 to 1990 population growth accounts for little of the variance seen inter-regionally in carbon dioxide emissions over the period. Thus addressing population growth may not be the most important factor in reducing environmental degradation with respect to carbon dioxide emissions. This same implication extends to other environmental issues. Even so, Preston is quick to point out that population policies may be the most cost-effective way of addressing such problems (Preston, 1996).
By examining the work of Jolly and Preston one can make several conclusions regarding the link between population trends and the environment. The first, as pointed out by Jolly, is that there are many ways of viewing the relationship between population growth and environmental degradation. Secondly, which of these frameworks for making conclusions about the relationship is most accurate is yet to be determined due to a lack of empirical analyses. Preston argues that population growth has negatively impacted natural resources, but the ability of human beings to mitigate the effects of population growth is underplayed in most analyses of the relationship between land degradation and population growth. Ultimately, population growth has the capability of impacting the environment; whether it is the underlying cause for land degradation and should be the emphasis of policies to alleviate environmental problems is not yet clear.
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