Wednesday, October 7, 2009

Population Growth Over Human History

"Go Forth And Multiply!" That's what the human population has successfully been doing for thousands and thousands yeras, expanding, exploring, migrating, conquering, utilizing, evolving, civilizing, industrializing, and now, destroying the very land upon we live.

Past Human Population Growth

The human population growth of the last century has been truly phenomenal. It required only 40 years after 1950 for the population to double from 2.5 billion. This doubling time is less than the average human lifetime. The world population passed 6 billion just before the end of the 20th century. Present estimates are for the population to reach 8-12 billion before the end of the 21th century. Of the 6 billion people, about half live in poverty and at least one fifth are severely undernourished. The rest live out their lives in comparative comfort and health. the factors affecting global human population are very simple. They are fertility, mortality, initial population, and time. The current growth rate of ~1.3% per year is smaller tahn the peak which occured a few decades ago (~2.1% per year in 1965-1970), but since this rate acts on much larger population base, the absolute number of new people per year (~90 million) is at an all time high. The stabilization of population will require a reduction in fertility globally. In the most optimistic view, this will take some time.


The current growth of population is driven by fertility. The more developed countries have lower fertility rates than the less developed countries. The fertility rates in the developed world are close to replacement levels, while the rates in the developing world are much higher. Thus, population growth and levels of developement are clearly linked. Fertility is largely controlled by economics and by human aspirations. the high fertility of the developing world can be partially explained by the large number of hands needed to perform low-technology agricultural tasks. In these areas, families with large numbers of children realize that having more children decreases rather than increases their standard of living. A dramatic example of this effect occured in Thailand, where, as soon as parents realized that future economic status was linked to the secondary schooling, which is expensive in Thailand, the fertility rate dropped from about 6 to 2 in a decade!


Mortality, or the death rate per individual, is another determining factor of population growth. In the developing world, the death rate has dropped, more or less continously, since the start of the industrial revolution. The combination of decreasing death rate to the narch of progress in sanitation and medicine, coupled with the decrease in birth rate due to changes in the economies, has led to a profound change in the population growth curve in the developed world. This changes is called the Demographic Transition.

Future Global Population Growth

Anyone who examines world population over the past two centuries certainly must be astounded, and quite possibly alarmed. The global population reached one billion in 1804. in 1927, some 123 years later, it passed two billion. sixty years later, in 1987, the world population was five billion, and 12 years later, in October 1999, it is estimated to have passed six billion. small wonder that many are concerned about this bodes for our future. due to the momentum represented by steeply pyramidal age distribution, population growth surely will continue for one to several generations. Most of that growth will occur in developing nations. an eventual world population of 8-12 billion is expected by the end of the century. but estimates change frequently. According to a report from the United Nations Population Fund, based on 1998 analyses, projections for the future global population are being revised downward. the projection for 2050 now is 8.9 billion, substantially lower than the 1996 projection of 9.4 billion.


No comments:

Post a Comment