Environmental Engineering Reference
In-Depth Information
Society
Until two centuries ago, human activity had little impact on the Earth's global systems. Since
the discovery of fossil fuels, society's need for resources has risen constantly as a consequence
of a growing population, mounting wealth, and increasing standards of living. This has put a
huge pressure on the environment, including the exploitation of resources as well as the
disposal of by-products generated during the process. The need for resources can be measured
by the global consumption of energy, which increased by 84 percent between 1970 and 1997,
loss of global biodiversity, transformation of land for agriculture to urban development,
alteration of biogeochemical cycles, and so on. (Steffen et al., 2004).
Increasing population
According to estimations, the world population was about 300 million at the dawn of the first
century (zero AD). It took approximately 1600 yeas for the world population to double to 600
million, and by 1900 the world population grew to around 1.7 billion. It was not until the
twentieth century that the planet witnessed an explosion in population growth. During this
century, the world population rose 3.5 times, from 1.65 billion to 6 billion on October 12,
1999. This was an average of 2.04 percent of growth per year. According to the United Nations
Population Division, the rate of grow has fallen from this 2.04 percent to around 1.3 percent
today (United Nations, 1999).
Population growth is affected by four distinctive factors:
initial population, fertility rate,
mortality rate,
and
time
. The rate at which the population increases is called the
rate of natural
increase
, which in mathematical terms is described as the
death rate
subtracted from the
birth
rate
. The birth rate, expressed as number of births per 1,000 per year, is a function of the
fertility rate that is defined as the number of children that would be born to a woman during
her child-bearing years (Rowland, 2003).
Paradoxically, fertility rate inversely correlates with the gross domestic product (GDP) of
a country. As can be seen in Figure 2.7, the higher the GDP of a nation the lower the fertility
rate is and vice versa. Exceptions to this rule are many oil-producing nations with high GDPs
(e.g., Oman, Gabon, Equatorial Guinea, and Saudi Arabia) in which their fertility rates are
much higher than for countries with similar GDPs. This outlier behavior is so that even when
these countries have a high income per inhabitant, the uneven wealth distribution does not
correlate with the average population's living standards.
The inverse correlation between a country's income and fertility rate is often referred as
demographic-economic paradox
(Kröhnert and Klingholz, 2008). There are different
explanations for this paradox. One is about mechanization. The most industrialized a nation
is the least labor needs so women have fewer children. Less-developed countries rely more
on manual labor and larger families are preferred to assist with the daily subsistence jobs.
Some countries have government assistance programs that are paid on per-child bases, so
this support becomes an incentive for many families to have a larger number of children.
Also, the lack of knowledge about human reproductive biology combined with restricted
access to contraceptives, which is many times opposed by religious beliefs, can cause
individuals to be more open to having a larger family. However, the bottom line is
probably
education. Higher incomes combined with education changes the perspective in the lives of
many individuals and then the need for having many children is substituted by other
purposes in life. In industrialized nations, the number of children is usually decided in
terms of the capability parents have to fill their offsprings' needs of heath, education, and
personal growth.
