Study Guide
Chapter 6
HISTORY AND GLOBAL
DISTRIBUTION 1
6.1 HISTORY AND GLOBAL DISTRIBUTION
6.1.1 INTRODUCTION
A population is a group of individuals living together in a given area at a given time. Changes in populations
are termed population dynamics . The current human population is made up of all of the people who
currently share the earth. The rst humans walked the planet millions of years ago. Since that time, the
number of humans living on the planet and where they live has constantly changed over time. Every birth
and death is a part of human population dynamics. Each time a person moves from one location to another,
the spatial arrangement of the population is changed, and this, too, is an element of population dynamics.
While humans are unique in many ways as a species, they are sub ject to many of the same limiting forces
and unexpected events of all populations of organisms. In 1999, the human population crossed the six billion mark. At current growth rates, the population will
double within 50 years. Long ago, when the human population was small, the doubling of the population
had little impact on the human population or its environment. However, with the size of today's population,
the eect of doubling the population is quite signicant. Already, most of the people of the world do not
have adequate clean water, food, housing and medical care, and these deciencies are at least partially the
result of over population. As the population continues to grow, competition for resources will increase.
Natural disasters and political conicts will exacerbate the problems, especially in the more stressed regions
of developing nations. The survivors of this competition will likely be determined by factors such as place
of birth and educational opportunities.
6.1.2 POPULATION GROWTH
Human populations are not stagnant. They naturally change in size, density and predominance of age
groups in response to environmental factors such as resources availability and disease, as well as social and
cultural factors. The increases and decreases in human population size make up what is known as human
population dynamics . If resources are not limited, then populations experience exponential growth. A
plot of exponential growth over time resembles a "J" curve. Absolute numbers are relatively small at rst
along the base of the J curve, but the population rapidly skyrockets when the critical time near the stem
of the J curve is reached. For most of the history of modern humans (Homo sapiens), people were hunter-gatherers. Food, especially
meat from large mammals, was usually plentiful. However, populations were small because the nomadic life 1
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CHAPTER 6. HISTORY AND GLOBAL DISTRIBUTION
did not favor large family sizes. During those times, the human population was probably not more than a
few million worldwide. It was still in the base of the J growth curve. With the end of the last Ice Age, roughly 10,000 years ago, the climates worldwide changed and many
large mammals that had been the mainstay of human diet became extinct. This forced a change in diet and
lifestyle, from one of the nomadic hunter-gatherer to that of a more stationary agricultural society.
Humans began cultivating food and started eating more plants and less meat. Having larger families was
possible with the more stationary lifestyle. In fact, having a large family increasingly became an asset, as
extra hands were needed for maintaining crops and homes. As agriculture became the mainstay of human
life, the population increased. As the population increased, people began living in villages, then in towns and nally in cities. This
led to problems associated with overcrowded conditions, such as the buildup of wastes, poverty and disease.
Large families were no longer advantageous. Infanticide was common during medieval times in Europe, and
communicable diseases also limited the human population numbers. Easily spread in crowded, rat-infested
urban areas, Black Death, the rst ma jor outbreak of the Bubonic Plague (1347-1351) drastically reduced
the populations in Europe and Asia, possibly by as much as 50 percent. Starting in the 17th Century, advances in science, medicine, agriculture and industry allowed rapid growth
of human population and infanticide again became a common practice. The next big inuence on the human population occurred with the start of the Industrial Revolution
in the late 18th century. With the advent of factories, children became valuable labor resources, thereby
contributing to survival, and family sizes increased. The resulting population boom was further aided
by improvements in agricultural technology that led to increased food production. Medical advancements
increased control over disease and lengthened the average lifespan. By the early 19th century, the human
population worldwide reached one billion. It was now in the stem of the J curve graph. As the world
approached the 20th century, the human population was growing at an exponential rate. During the 20th century, another important event in human population dynamics occurred. The birth
rates in the highly developed countries decreased dramatically. Factors contributing to this decrease included:
a rise in the standard of living, the availability of practical birth control methods and the establishment of
child education and labor laws. These factors made large families economically impractical. In Japan, the
birth rate has been so low in recent years that the government and corporations are worried about future
labor shortages. Therefore, they are actively encouraging population growth. In contrast, the populations
in less well-developed countries continue to soar. Worldwide, the human population currently exceeds six
billion and continues to grow exponentially. How much more the world population will grow is a topic of
intense speculation. One thing is certain: exponential growth cannot continue forever, as earth's resources
are limited.
6.1.3 POPULATION DEMOGRAPHICS
Human demography (population change) is usually described in terms of the births and deaths per 1000
people. When births of an area exceed deaths, population increases. When the births of an area are fewer
than deaths, the population decreases. The annual rate at which the size of a population changes is: Figure 6.1
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During the year 2000, the birth rate for the world was 22 and the death rate was 9. Thus, the world's
population grew at a rate of 1.3 percent. The annual rate of population change for a particular city or region
is also aected by immigration(movement of people into a region) and emigration(movement out of a
region). Figure 6.2
Highly industrialized nations, like the United States, Canada, Japan and Germany, generally have low
birth and death rates. Annual rates of natural population change vary from -0.1% to 0.5%. In some industrial
nations (e.g. Germany and Russia) death rates exceed birth rates so the net population decreases over time.
Newly industrialized countries (e.g. South Korea, Mexico and China) have moderate birth rates and low
death rates. The low death rates result from better sanitation, better heath care and stable food production
that accompany industrialization. The annual rates of natural population change are about 1 percent to 2
percent in these countries. Countries with limited industrial development (e.g. Pakistan and Ethiopia) tend
to have high birth rates and moderate to low death rates. These nations are growing rapidly with annual
rates of natural population change exceeding 2 percent. Several factors inuence human fertility. Important factors inuencing birth and fertility rates in
human populations are: auence, average marriage age, availability of birth control, family labor needs,
cultural beliefs, religious beliefs and the cost of raising and educating children. The rapid growth of the world's population over the past 100 years is mainly results from a decline in
death rates. Reasons for the drop in death rates include: better nutrition, fewer infant deaths, increased
average life span and improvements in medical technology. As countries become developed and industrialized, they experience a movement from high population
growth to low population growth. Both death and birth rates decline. These countries usually move from rapid population growth, to slow growth, to zero growth and nally
to a reduction in population. This shift in growth rate with development is called the " demographic
transition ." Four distinct stages occur during the transition: pre-industrial, transitional, industrial and
post-industrial. During the pre-industrial stage , harsh living conditions result in a high birth rate and a high death rate.
The population grows very slowly, if at all. The transitional stagebegins shortly after industrialization.
During this phase, the death rate drops because of increased food production and better sanitation and
health conditions, but, the birth rate remains high. Therefore, the population grows rapidly. During the industrial stage , industrialization is well established in the country. The birth rate drops
and eventually approaches the death rate. Couples in cities realize that children are expensive to raise and
that having large families restrict their job opportunities. The post-industrialstage occurs when the birth
rate declines even further to equal the death rate, thus population growth reaches zero. The birth rate may
eventually fall below the death rate, resulting in negative population growth. The United States and most European countries have experienced this gradual transition over the past
150 years. The transition moves much faster for today's developing countries. This is because improvements
in preventive health and medical care in recent decades have dramatically reduced mortality especially
infant mortality and increased life expectancy. In a growing number of countries, couples are having
fewer children than the two they need to "replace" themselves. However, even if the level of " replacement
fertility " were reached today, populations would continue to grow for several decades because of the large
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CHAPTER 6. HISTORY AND GLOBAL DISTRIBUTION
numbers of people now entering their reproductive years. As a result of reduced fertility and mortality, there will be a gradual demographic shift in all countries
over the next few decades towards an older population. In developed countries, the proportion of people
over age 65 has increased from 8 to 14 percent since 1950, and is expected to reach 25 percent by 2050.
Within the next 35 years, those over age 65 will represent 30 percent or more of the populations in Japan
and Germany. In some countries, the number of residents over age 85 will more than double.
6.1.4 PATTERNS OF RESOURCE USE
Humans have always made an impact on the environment through their use of resources. Early humans were
primarily hunter-gatherers who used tools to survive. They fashioned wood and stone tools for hunting and
food preparation, and used re for cooking. Early humans developed methods for changing habitat to suit
their needs and herding wild animals. As time passed, humans developed more tools and techniques and
came to rely on that technology in their daily lives. Although the tools of early humans were primitive by
today's standards, they signicantly aected the environment and probably hastened the extinction of some
large Ice Age mammals. After the end of the last Ice Age, some eight to 10,000 years ago, humans began domesticating wild
animals and plants. The rst known instance of farming started in a region extending from southeastern
Turkey to western Iran, known as the fertile crescent.
These early farmers domesticated crops such as chickpea, bitter vetch, grapes, olives, barley, emmer
wheat, lentils, and ax. They hybridized wheat for making bread from wild grass and emmer wheat. They
also domesticated animals such as sheep, goats, cattle and pigs. The fertile crescent's unique diversity of
wild crops and animals oered humans a mix of basic agricultural commodities that allowed a revolution
in the development of human society. With a reliable food supply, humans were able to stay in one place
and be assured of having a constant supply of carbohydrates, protein, milk and oil. They had animals for
transportation and plant and animal materials for producing clothing and rope. Agricultural economies soon
displaced hunter-gatherer economies. Within 2,000 years, farming ranged from Pakistan to southern Italy. Most early agriculture was subsistence farming in which farmers grew only enough food to feed their
families. Agriculture underwent another important revolution about 5,000 years ago with the invention of
the plow. The plow allowed humans to clear and farm larger plots of land than was otherwise possible. This
increased the food supply and a concomitant increase in human population growth. More ecient farming
methods also resulted in urbanization because a few farmers could produce a large surplus of food to feed
those in the urban areas. Over the last 10,000 years, land clearing for agriculture has destroyed and degraded the habitats of many
species of plants and animals. Today, growing populations in less developed countries are rapidly clearing
tropical forests and savannas for agricultural use. These tropical rainforests and savannas provide habitat
for most of the earth's species. It has become clear that modern agricultural practices are not sustainable.
Once-fertile areas are becoming infertile because of overgrazing, erosion and nutrient depletion. Furthermore,
modern agriculture requires large inputs of energy and fertilizers, usually produced from nonrenewable fossil
fuels. The next ma jor cultural change, the Industrial Revolution, began in England in the mid-18th century.
It involved a shift from small-scale production of goods by hand to large-scale production of goods by ma-
chines. Industrial production of goods increased the consumption of natural resources such as minerals fuel,
timber and water by cities. After World War I, more ecient mass production techniques were developed,
and industrialization became prevalent in the economies of the United States, Canada, Japan and western
Europe. Advanced industrialization leads to many changes in human society, and some of those changes negatively
aect the supply of natural resources and result in environmental degradation. These changes include:
increased production and consumption of goods by humans, dependence on non-renewable resources such as
oil and coal, production of synthetic materials (which may be toxic or non-biodegradable) and consumption
of large amounts of energy at home and work.
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Other changes may have positive benets. These include: creation and mass production of useful and
aordable products, signicant increases in the average Gross National Productper person, large increases
in agricultural productivity, sharp rises in average life expectancy and a gradual decline in population growth
rates. The information age was born with the invention of miniaturized electronics such as integrated circuits
and computer central processing units. This stage in human development has changed and continues to
change society as we know it. Information and communication have become the most-valued resources.
This shift in turn, may lessen our inuence on the earth's environment through reduced natural resource
consumption. For instance, in recent years energy use in the United States has not increased to the extent
expected from economic growth. Online shopping, telecommuting and other Internet activities may be
lessening human energy consumption. By making good use of information technologies, less developed countries may be able to reduce potential
environmental problems as their economies expand in the future. With so much information easily available,
developing countries may not repeat the environmental mistakes that more developed countries made as they
became industrialized.
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CARRYING CAPACITY 1
7.1 CARRYING CAPACITY
7.1.1 INTRODUCTION
The human carrying capacity is a concept explored by many people, most famously Thomas Robert Malthus
(1766 - 1834), for hundreds of years. Carrying capacity, "K,"refers to the number of individuals of a
population that can be sustained indenitely by a given area. At carrying capacity, the population will have
an impact on the resources of the given area, but not to the point where the area can no longer sustain the
population. Just as a population of wildebeest or algae has a carrying capacity, so does a human population. Humans, while sub ject to the same ecological constraints as any other species (a need for nutrients,
water, etc.), have some features as individuals and some as a population that make them a unique species.
Unlike most other organisms, humans have the capacity to alter their number of ospring, level of resource
consumption and distribution. While most women around the world could potentially have the same number
of children during their lives, the number they actually have is aected by many factors. Depending upon
technological, cultural, economic and educational factors, people around the world have families of dierent
sizes. Additionally, unlike other organisms, humans invent and alter technology, which allows them to change
their environment. This ability makes it dicult to determine the human K.
7.1.2 EFFECTS OF TECHNOLOGY AND THE ENVIRONMENT
When scholars in the 1700's estimated the total number of people that today earth could sustain, they were
living in a very dierent world than our world. Today airplanes can transport people and food half way
around the world in a matter of hours, not weeks or months, as was the case with ships in the 1700s. Today
we have sophisticated, powered farm equipment that can rapidly plow, plant, fertilize and harvest acres of
crops a day. One farmer can cultivate hundreds of acres of land. This is a far cry from the draft-animal
plowing, hand planting and hand harvesting performed by farmers in the 1700s. Additionally, synthetic
fertilizers, pesticides and modern irrigation methods allow us to produce crops on formerly marginal lands
and increase the productivity of other agricultural lands. With the increase in the amount of land that
each individual can farm, the food production has increased. This increased food production, in turn, has
increased the potential human K relative to estimates from the 1700s.
Whereas technological advances have increased the human K, changes in environmental conditions could
potentially decrease it. For example, a global or even a large regional change in the climate could reduce
K below current estimates. Coastal ooding due to rising ocean levels associated with global warming and
desertication of agricultural lands resulting from poor farming practices or natural climate variation could
cause food production to be less than that upon which the human carrying capacity was originally estimated. 1
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CHAPTER 7. CARRYING CAPACITY
There are those who believe that advances in technology and other knowledge will continue to provide
the means to feed virtually any human population size. Those who subscribe to this philosophy believe that
this continuous innovation will "save us" from ourselves and changes in the environment. Others believe that technology will itself reach a limit to its capabilities. This group argues that resources
on earth including physical space are limited and that eventually we must learn to live within our means.
Aside from the physical limitations of the earth's natural resources and food production capabilities, we
must consider the conditions we are willing to live with.
7.1.3 EFFECT OF STANDARD OF LIVING
Given the wherewithal to do so, humans have aesthetic expectations in their daily lives. This is a considera-
tion that is less evident in other species. While the earth might be able to hold many more than the current
human population of six billion (estimates of the human K with current technology go as high as 50 billion)
at some point people will nd it unacceptable to live with the crowding and pollution issues associated with
a dramatic increase in population. The qualitative measure of a person's or population's quality of life is
called its standard of living . It is associated not only with aesthetics of surroundings and levels of noise,
air and water pollution, but also with levels of resource consumption. Americans have one of the world's highest standards of living. While there are many who live in poverty
in the United States, on average we have relatively small families, large homes, many possessions, plentiful
food supplies, clean water and good medical care. This is not the case in most of the developing world. While many nations have larger average family sizes, they have smaller homes, fewer possessions and less
food. Supplies of clean water may be scarce and medical care may be inadequate. All people desire to have
adequate resources to provide good care for their families, and thus population in most developing countries
are striving for standard of living of developed nations.
Is it possible for all six billion people on earth to live at the same level of resource use as in the United
States, Japan and Western Europe? With current technology, the answer is "no." However, this does not
mean that the people of one nation are more or less entitled to a given standard of living than those of
another. What it does mean for citizens of nations like the United States is that we must reduce our current
use of resources. Of all of the food purchased by the average American family, 10 percent is wasted. In
addition, because most Americans are not vegetarians, we tend to eat high on the food chain, which requires
more resources than a vegetarian diet. Calculation of ecological eciency indicate that from one trophic level on the food chain to the next,
there is only a 10 percent eciency in the transfer of energy. Thus people who predominately eat more
grains, fruits and vegetables are getting more out of the energy required to produce the food than those who
eat a lot of meat. The calories that a person gets from beef are much fewer than the calories in the grain
required to raise the cattle. The person is better o skipping the middleman or middle cow in this case
and eating the grain. This is why many more people can be sustained on a diet that consists of a larger
percentage of rice, millet or wheat, rather than of sh, beef or chicken. In addition to resources used to provide food, Americans use disproportionate amounts of natural re-
sources such as trees (for paper, furniture and building, among other things) and fossil fuels (for automobiles,
homes and industry). We also produce a great amount of "quick waste." Packaging that comes on food in
the grocery store is a good example of quick waste. The hard plastic packaging used for snack foods that is
immediately removed and thrown away and plastic grocery bags are both examples of quick waste. Thus,
patronizing fast food restaurants increases resource consumption and solid waste production at the same
time. The good news for the environment (from both a solid waste and a resource use standpoint) is that we
can easily reduce the amount of goods and resources that we use and waste without drastically aecting
our standard of living. By properly inating car tires, America could save millions of barrels of oil annually.
If we were to use more renewable energy resources like solar and wind power as opposed to petroleum
and nuclear energy there would be a reduced need to extract non-renewable resources from the earth. The
amount of packaging used for goods could also be reduced. Reusable canvas bags could be used for shopping
and plastic and paper grocery bags could be reused.
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At home, many waste materials could be recycled, instead of being thrown away. These relatively easy
steps could reduce the overall ecological impact that each person has on the earth. This impact is sometimes
termed a person's ecological footprint . The smaller each person's ecological footprint, the greater the
standard of living possible for each person.
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CHAPTER 7. CARRYING CAPACITY
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