Population Growth as a Driving Force of Global & Environmental Changes
BY DAVID W. WONG
Two recent events attracted different levels of attention nationally and globally. After several decades of debates and rigorous research, and the discovery of hard evidence, climatologists and Earth scientists have come to the conclusion that global warming is not a hypothesis anymore but a fact. Global warming has triggered various policy debates globally and nationally and resulted in the Kyoto Treaty, among other efforts, to reduce green house gases. When the US population reached 300 million last year, just 39 years after reaching 200 million in 1967, public concern about population growth was minimal and no serious discussion on the issue was initiated by policymakers. While the 300 million marker for the US was a symbolic milestone with no real significance, the larger issue of population growth is not trivial.
Numerous scholars have highlighted the connections between population growth and environmental degradation, though many of those ideas were controversial. Examples include the “tragedy of the commons” proposed by Garrett Hardin, the “population bomb” suggested by Paul Ehrlich and “the environmental cost of economic growth” identified by Barry Commoner. The work of these scholars offers many implications on the relationships between population and global change. Among these implications, two of them warrant particular attention.
First, global environmental issues are not just related to the size of population, but also to the behavior of the population. An average individual in a developed country likely has a larger environmental impact than an individual in a developing country in terms of natural resources consumption. In other words, human behavior is critical in understanding the human impacts on global and environmental changes. Second, while these scholars highlighted the roles of human population in altering the natural systems, most scientists addressing global environmental problems focus on the superficial manifestations of the problems or adopt a technocratic approach, partly due to the overwhelming technological advancements that have occurred in the past several decades. The connection between these problems and population, the fundamental source of most if not all environmental problems, has not been in the mainstream of science. It is reasonable to expect that without addressing the fundamental issues of population growth and behavior, the current symptomatic approach may not accomplish as much as we hope.
GLOBAL AND ENVIRONMENTAL ISSUES
Global warming probably has received the most attention among various far-reaching environmental issues. Much evidence, such as the breaking up of a major ice cap off Antarctica and the receding sea ice cover in the Arctic, substantiates the claim of rising global temperature. Wild life habitats and their life cycles have been affected by climate change, as reported by numerous documentaries and movies, including “The March of the Penguins” and “Inconvenient Truth.” Coral reefs are extremely sensitive to temperature change. It is expected that due to the rise in sea water temperature, the sizes of coral reef colonies will decline. Though the impacts of global warming are not uniform across the globe at all times, its impacts are felt by different parts of world in different times.
Many global and environmental change problems may be localized or manifested at the regional scale. The expansion of desert (desertification) is found only in the peripheries of desert regions. As the size of vegetative cover declines and more bare soil is exposed, the frequency of dust storms has been increasing. Though dust storms travel across continents their impacts are not felt everywhere around the globe. The disappearance of tropical rainforests, one of the most critical biomasses on Earth, occurs only in tropical regions however the decline of such rainforests also slows down the carbon cycle process and thus affects the global climate. Therefore, many local activities will have global impacts.
While it may not be possible to link all these global/local and environmental changes directly to human activities, the connections do exist at different causative levels. Global warming is related to the amount of green house gases (GHGs) and aerosols in the air, but human activities are not the only sources of general GHGs and aerosols. Similarly, the overgrazing at the desert peripheries and the sand drifting process can both contribute to desertification. On the other hand, it is obvious that the expansion of urban areas and logging activities are direct actions leading to the decline of tropical rainforests. It is often not straight-forward to relate human activities to all global environmental issues, but their roles in global and environmental change is undeniable.
HISTORY AND DYNAMICS OF POPULATION GROWTH
As the world’s population continues to grow, we should expect that human impacts on the global and environmental systems will increase. The history of population growth has gone through several dramatic stages. Estimates of the world’s population indicate that the global population was very small for many centuries —well below 1 billion before 1800 AD. So far, approximately 50 billion people have ever lived on Earth, but more than 6 billion (>10%) are still alive. Population grew exponentially after 1800 AD and reached the 1 billion mark in the early 1800s. Population growth continued after the 19th century while the environmental quality degraded more. But in 2000 (200 years later), the world population has increased by six-fold, exceeding 6 billion. In short, the increase in world population has been a recent phenomenon.
One of the primary reasons that population grew relatively fast after 1800 AD was most countries in the world had gone through “the demographic transition.” The demographic transition model was first developed based upon the demographic experience of European countries in terms of changes in birth rate, death rate and growth rate. The transition can be described in three or four stages. During the first stage, both the birth rate and death rate are high and therefore population growth was limited. During the second stage, the death rate declined gradually mainly due to medical advancement. Because the gap between the birth rate and death rate increased, population started increasing (the growth rate increased). Gradually, the population developed the incentive to give birth to fewer children due in part to lowered infant mortality rate and the shift to economies requiring less labor. As a result, the birth rate started to decline during the third stage while the death rate continued to decline. The significant gap between the birth and death rates still existed but it gradually reduced. At the fourth stage, the birth rate continued to decline converging with the death rate. As a result, the population growth became minimal.
Most western or developed countries have completed this transition. During stages two and three, population growth was the most significant and the world population increased significantly. But when less developed countries experienced the demographic transition recently, the death rate declined at a much faster rate due to life-saving medical technology was readily available to those countries. On the other hand, because of the cultural inertia favoring large families and the need for labor in the predominantly agricultural economies, the birth rate in those countries maintained at a high level for a longer time and resulted in what was characterized as a population explosion.
Figure 1 shows the demographic transitions of Sweden, which represents developed countries, and that of Mexico, which represents developing or less developed countries. The differences between crude birth rate (CBR) and crude death rate (CDR) and the resultant population growths between the two countries are apparent. Even back to 1900, the death rate of Sweden was quite low and the difference between birth rate and death rate was not very large. In 1930, the birth rate dropped to the level similar to the death rate and two rates converged closely in 1980. But in Mexico, the death rate declined drastically between 1930 and 1950, and the birth rate was maintained at a high rate until 1970 before it declined gradually.
No doubt that the demographic transition experienced by western countries and the recent population explosion experienced by the developing countries created a long term surge of population lasting for almost two centuries. Recent reports indicate that some developed countries, such as France and Japan, have experienced a new phase in the transition: death rate exceeds birth rate, resulting in a negative growth in population. In developing countries however significant population growth is still the norm. Being the largest country in population, the drastic one-child policy, though not without controversies and many side effects, has kept the Chinese population growth rates to the levels comparable to many western nations. Despite the low rates, the absolute increases of such a large population have been enormous. Similarly, the population increase in India is also alarming as this second largest country does not have any aggressive population policy. It is anticipated that Indian population will catch up with the Chinese population by 2037.
Increased population definitely exerts pressure on the natural environment in developed nations; efficiently utilizing technology can help conserve resources. In general, an individual in a developed nation will likely consume more natural resources than someone in a poorer country. As certain countries become more developed economically, their immense populations will surely impose great pressure on the environment by numbers if not by rate of per capita resource use.
As a result, countries experiencing most environmental problems are those non-western countries striving for economic growth such as the former Soviet bloc countries. Recently, China, India, and Mexico with relatively large populations become major global economic powers as their economies are progressing toward the levels of developed nations. Their huge population sizes combined with rising economic well-being forms a major force to exploit the natural resource and press on the environment. The magnitudes of these impacts may be felt globally because of their massive populations.
Two departments in Mason’s College of Science, Earth Systems & GeoInformation Sciences and Environmental Science & Policy, jointly offer a new BS degree in Global and Environmental Change commencing in Fall 2007. This degree has two tracks: global change and environmental change. The degree is the natural science counterpart of the BA degree in Global Affairs which emphasizes the social and cultural dimensions. The new degree has a focus on the physical environment and systems, and the human dimension is recognized as an important component in the curriculum. We believe that without understanding human population dynamics, pure science cannot tackle problems in global and environmental changes.
David W. Wong (dwong2@gmu.edu) is professor and chair of the department of Earth Systems & GeoInformation Sciences (http://esgs.gmu.edu) in the College of Science. The author is gracious to the inputs provided by Mason Professor Sheryl Beach to an earlier version of this article.
