ESS Topic 8.1 - Human population dynamics guide

8.1 Human population dynamics guide p. 1
IB Environmental Systems and Societies
Objective:
In this study guide, you will:
● Describe the pattern of human population growth .
● Explain exponential growth and its implications for human population
● Review population growth models and carrying capacity in the biosphere.
● Interpret population pyramids
● Describe the demographic transition model
● Discuss the use of models to predict population growth.
● Calculate crude birth rate , crude death rate , fertility , doubling time and natural increase
rate .
● Draw a population pyramid from given data.
● Identify demographic transition stages from population pyramids.
Human population growth
Demography is the study of the statistical characteristics of human populations, e.g. total size, age
and sex composition, and changes over time with variations in birth and death rates.
1. Use Table 1 below to plot a human population growth curve from 1000 AD to the present
on the grid provided. Your graph should be scaled appropriately and include labels and units
of measurement for both the x-axis and y-axis.
Table 1: Human population (in billions) from 2000 years before present until 2055
Date Pop’l. Date Pop’l. Date Pop’l. Date Pop’l.
1000 0.40 1927 2.00 1974 4.00 2010 6.80
1500 0.50 1950 2.50 1980 4.50 2013 7.00
1804 1.00 1960 3.00 1987 5.00 2028 8.00
1880 1.50 1970 3.50 1999 6.00 2055 9.00

Exponential growth is characterized by increasingly short doubling times. Doubling time is the
number of years it would take to double the size of a population at a particular rate (%) of growth.
For example, with a 2% growth rate or natural increase rate (NIR) , the population doubling time
would be about 35 years, with 4% natural increase rate a population will double in about 17 years.
2. How long would it take for a population to double if the natural increase rate were…
a. 1%?
b. 3%
c. 5%
3. Use Table 1 to calculate the doubling times for the global human population since 1500 AD.
Date population doubling
time (years)
date population doubling
time
1500 0.5 1500 5.0
1800 1.0 300 6.0
1927 2.0 7.0
3.0 8.0
4.0 9.0
Exponential Growth
Read The Persian Chessboard, the article on exponential increase by Joseph Fourier, and answer
the questions which follow.
THE PERSIAN CHESSBOARD
by JOSEPH FOURIER, Analytic Theory of Heat, Preliminary Discourse (1822)
The way I first heard the story, it happened in ancient Persia. But it may have been India or
even China. Anyway, it happened a long time ago. The Grand Vizier, the principal advisor to the
King, had invented a new game. It was played with moving pieces on a square board comprised of
64 red and black squares. The most important piece was the King. The next most important piece
was the Grand Vizier - just what we might expect of a game invented by a Grand Vizier. The object
of the game was to capture the enemy King, and so the game was called, in Persian, shahmat-shah
for King, mat for dead. Death to the King. In Russian it is still called shakhmat, which perhaps
conveys a lingering revolutionary sentiment. Even in English there is an echo of this name - the final
move is called "checkmate." The game, of course, is chess. As time passed, the pieces, their
moves, and the rules of the game all evolved; there is, for example, no longer a Grand Vizier-it has
become transmogrified into a Queen, with much more formidable powers.
Why a King should delight in the invention of a game called "Death to the King" is a mystery.
But, so the story goes, he was so pleased that he asked the Grand Vizier to name his own reward

for so splendid an invention. The Grand Vizier had his answer ready: He was a modest man, he told
the Shah. He wished only for a modest reward. Gesturing to the eight columns and eight rows of
squares on the board he had invented, he asked that he be given a single grain of wheat on the first
square, twice that on the second square, twice that on the third, and so on, until each square had its
complement of wheat. No, the King remonstrated, this is too modest a reward for so important an
invention. He offered jewels, dancing girls, palaces. But the Grand Vizier, his eyes becomingly
lowered, refused them all. It was little piles of wheat that he craved. So, secretly marvelling at the
humility and restraint of his counsellor, the King consented.
When, however, the Master of the Royal Granary began to count out the grains, the King faced an
unpleasant surprise. The number of grains starts out small enough: 1, 2, 4, 8, 16, 32, 64, 128, 256,
512, 1024 . . . but by the time the 64th square is approached, the number of grains becomes
colossal, staggering. In fact, the number is nearly 18.5 quintillion. Perhaps the Grand Vizier was on
a high-fibre diet.
How much does 18.5 quintillion grains of wheat weigh? If each grain is a millimetre in size, then all
of the grains together would weigh around 75 billion metric tons, which far exceeds what could have
been stored in the Shah's granaries. In fact, this is the equivalent of about 150 years of the world's
present wheat production. An account of what happened next has not come down to us. Whether
the King, in default, blaming himself for inattentiveness in his study of arithmetic, handed the
kingdom over to the Vizier, or whether the latter experienced the tribulations of a new game called
viziermat, we are not privileged to know.
The story of the Persian Chessboard may be just a fable. But the ancient Persians and Indians were
brilliant pathfinders in mathematics, and understood the enormous numbers that result when you
keep on doubling. Had chess been invented with 100 (10 X 10) squares instead of 64 (8 X 8), the
resulting debt in grains of wheat would have weighed as much as the Earth. A sequence of numbers
like this, where each number is a fixed multiple of the previous one, is called a geometric
progression, and the process is called an exponential increase.
Exponentials show up in all sorts of important areas, unfamiliar and familiar. The most
common circumstance in which repeated doublings, and therefore exponential growth, occurs is in
biological reproduction. Consider first the simple case of a bacterium that reproduces by dividing in
two. After a while, each of the two daughter bacteria divides as well. As long as there's enough food
and no poisons in the environment, the bacterial colony will grow exponentially. Under very
favourable circumstances, there can be a doubling every 15 minutes or so. That means 4 doublings
an hour and 96 doublings a day. Although a bacterium weighs only about a trillionth of a gram, its
descendants, after a day of wild asexual abandon, will collectively weigh as much as a mountain; in
a little over a day and a half as much as the Earth; in two days more than the Sun. . . . And before
very long, everything in the Universe will be made of bacteria. This is not a very happy prospect,
and fortunately it never happens. Why not? Because exponential growth of this sort always bumps
into some natural obstacle. The bugs run out of food, or they poison each other, or are shy about
reproducing when they have hardly any privacy. Exponentials can't go on forever, because they will
gobble up everything. Long before then they encounter some impediment.
Exponentials are also the central idea behind the world population crisis. For most of the
time humans have been on Earth the population was stable, with births and deaths almost perfectly
in balance. This is called a "steady state." After the invention of agriculture including the planting
and harvesting of those grains of wheat the Grand Vizier was hankering for--the human population
of this planet began increasing, entering an exponential phase, which is very far from a steady state.

Right now the doubling time of the world population is about 40 years. Every 40 years there will be
twice as many of us. As the English clergyman Thomas Malthus pointed out in 1798, a population
increasing exponentially-Malthus described it as geometrical progression-will outstrip any
conceivable increase in food supply. No Green Revolution, no hydroponics, no making the deserts
bloom can beat an exponential population growth.
There is also no extraterrestrial solution to this problem. Right now there are something like
240,000 more humans being born than dying every day. We are very far from being able to ship
240,000 people into space every day. No settlements in Earth orbit or on the Moon or on other
planets can put a perceptible dent in the population explosion. Even if it were possible to ship
everybody on Earth off to planets of distant stars on ships that travel faster than light, almost nothing
would be changed, all the habitable planets in the Milky Way galaxy would be full up in a millennium
or so. Unless we slow our rate of reproduction. Never underestimate an exponential!
4. Write a definition of exponential growth:
5. What is the trend in the changing doubling times of human populations shown in Table 1
over the past 2000 years?
Exponential growth and implication for the human population
There are two main theories relating to population growth and food supply, namely Malthus and
Boserup.
Malthusian theory
Thomas Malthus was an English clergyman and economist who lived from 1766 to 1834. In his text
An essay on the principle of population, 1798, Malthus expressed a pessimistic view over the
dangers of over-population and claimed that food supply was the main limit to population growth.
Malthus believed that the human population increases geometrically (i.e. 2, 4, 8, 16, 32, etc.)
whereas food supplies can grow only arithmetically (i.e. 2, 4, 6, 8, 10, 12, etc.) being limited by
available new land. Malthus added that the 'laws of nature' dictate that a population can never
increase beyond the food supplies necessary to support it.
According to Malthus, population increase is limited by certain 'checks'. These prevent numbers of
people increasing beyond the optimum population, which the available resources cannot support.
As long as fertile land is available, Malthus believed that there would be more than enough food to
feed a growing population. However, as population and the demands for food increase, there is a
greater pressure to farm more intensively and cultivate poorer, more marginal land. According to
Malthus, though, food production can only increase to a certain level determined by the productive
capacity of the land and existing levels of technology.

Beyond the ceiling where land is used to its fullest extent, over cultivation and, ultimately, soil
erosion occurs, contributing to a general decline in food production. This is known as the law of
diminishing returns where, even with higher levels of technology, only a small increase in yield will
eventually occur. These marginal returns ultimately serve as a check to population growth. Malthus
did acknowledge that increases in food output would be possible with new methods in food
production, but he still maintained that limited food supply would eventually take place and so limit
population.
Limitations of Malthusian theory
Anti-Malthusians criticise the theory as being too simplistic. A shortage of food is just one possible
explanation for Malthus’ reasoning (geometric population growth which outruns an arithmetic
increase in food supply). This ignores the reality that it is actually only the poor who go hungry.
Poverty results from the poor distribution of resources, not physical limits on production. Except on a
global scale, the world's community is not 'closed' and so does not enjoy a fair and even distribution
of food supplies. Even so, Malthus could not possibly have foreseen the spectacular changes in
farming technology which mean we can produce enough food from an area the size of a football
pitch to supply 1000 people for a year, i.e. there is enough land to feed the whole world. Thus
evidence of the last two centuries contradicts the Malthusian notion of food supply increasing only
arithmetically. Rather than starvation, food surpluses exist and agricultural production increases. In
1992 European surpluses reached 26 million tonnes and there are indications that this trend will
continue, contrary to Malthusian theory.
Boserup's theory
In 1965, Esther Boserup, a Danish economist, asserted that an increase in population would
stimulate technologists to increase food production (the optimistic view). Boserup suggested that
any rise in population will increase the demand for food and so act as an incentive to change
agrarian technology and produce more food. We can sum up Boserup's theory by the sentence
'necessity is the mother of invention'.
Boserup's ideas were based on her research into various land use systems, ranging from extensive
shifting cultivation in the tropical rainforests to more intensive multiple cropping, as in South-East
Asia. Her theory suggests that, as population increases, agriculture moves into higher stages of
intensity through innovation and the introduction of new farming methods. The conclusion arising
from Boserup's theory is that population growth naturally leads to development.
Limitations of Boserup's theory
Like Malthus, Boserup's idea is based on the assumption of a 'closed' community. In reality, except
at a global scale, communities are not 'closed' because constant in- and out-migration are common
features. It has therefore been very difficult to test Boserup's ideas. This is because migration
usually occurs in areas of over-population to relieve the population pressure, which, according to
Boserup's theory, then leads to technological innovation.
Over-population can lead to unsuitable farming practices that may degrade the land. Consequently,
some geographers have partly blamed population pressure for desertification in the Sahel. From this
it is clear that certain types of fragile environment cannot support excessive numbers of people. In
such cases, population pressure does not always lead to technological innovation and development.

Application of Malthus and Boserup
There is evidence to suggest that the ideas of both Boserup and Malthus may be appropriate at
different scales. On a global level the growing suffering and famine in some developing countries
today may reinforce Malthusian ideas. On the other hand, at a national scale, some governments
have been motivated by increasing population to develop their resources and so meet growing
demands.
6. Summarise the Malthusian and Boserup models in the table below.
Malthus Boserup
Model
Diagram
Main ideas
Limitations
Applications

Study the graph below showing population and food supply in India.
7. As the population of India increased what happens to the per capita food supply? Why?
8. Add a third line on the graph to show increase in food production. Label each line.
9. Which of the above theories is represented by this data? Explain your reasoning.
10. Do you think that the concept of carrying capacity is applicable to the human population?
Use evidence from the textbook chapter and your reading in this study guide to justify your
response.

Global Population Growth
The pattern of human growth is not uniform with most growth currently taking place in developing
countries.
Use the following data to construct population growth curves for developed and developing regions
of the world from 1800 until 2100 AD. Your graph should show both curves on the same grid and
include appropriate labels and units of measurement for both x- and y-axes.
11. Plot both the developing regions and the developed regions. (Units are billions of people:
109
).
Table 2: Human Populations in MEDC’s and LEDC’s, 1800 - 2100 AD
(in billions of people, 109
)
Date Developed Developing Date Developed Developing
1800 0.3 0.7 1980 1.1 3.3
1850 0.4 0.8 1990 1.2 4.1
1900 0.6 1.1 2000 1.3 5.0
1950 0.8 1.7 2025 1.4 7.2
1960 0.9 2.1 2050 1.4 8.0
1970 1.0 2.8 2100 1.4 8.0
12. The values for the next century are only estimates. What will be the most important social
factor that will determine human population size? Why do you think so? Provide evidence
and/or reasons to support your answer.
Measures of Population Growth
13. What are the four main factors that affect population size of organisms?

Measures of population change are crude birth rate, crude death rate, and natural increase rate.
Crude birth rate is the number of births per thousand individuals in a population per year.
Crude death rate is the number of deaths per thousand individuals in a population per year.
14. Crude birth and death rates are calculated by dividing the number of births or deaths by the
population size and multiplying by 1000. Write these out as formulae:
Crude birth rate =
Crude death rate =
Natural increase rate is the rate of human growth expressed as a percentage change per year.
Natural increase rate* = (Crude birth rate - crude death rate) / 10 (*migration is ignored)
15. Calculate the population density, crude birth rate, crude death rate, and natural
increase rate from the data provided in Table 3 below and complete the table.
Table 3: Changes in Global Human Populations by Region
Region Pop’n
106
Land
Area
106
km2
Births
106
Deaths
106
Crude
birth
rate
Crude
death
rate
Natural
increase
rate
Pop’n
Density
World 6,000 131 121.0 55.8
Asia 3,500 31 88.2 29.4
India 1,000 3 29.0 10.0
Africa 730 29 30.7 10.0
Tanzania 30 0.9 1.3 0.4
Europe 730 22.7 8.5 8.2
Switzerland 7 0.04 0.09 0.07
N America 460 21.8 9.3 3.6
USA 270 9.6 4.3 2.4

16. Population density is defined as …
Fertility rate and predicted population growth
Population growth can be defined in terms of birth rate, doubling time and fertility rate.
Fertility rate is the average number of children that the women in a particular population have
during their lifetimes.
What will be the future world population?
Three billion women will decide the world population in 2050. A fertility rate of 2.0 means that a
couple replace themselves, and do not add to the population. In this scenario the population will
increase from 6 billion now to 10.8 billion. If every second woman decides to have three rather than
two children, a fertility rate of 2.5, the population will rise to 27 billion by 2150. If, however, every
second woman decides to have only one child instead of two, a fertility rate of 1.5, the world
population will sink to 3.6 billion. Total world fertility is now about 3.0, 1.7 in developed regions, and
averaging 3.4 (but up to 6.0) in developing regions. Fertility rate is falling although population size
continues to increase. The UN has calculated estimates for population change based on fertility
rates stabilising at 2.6 (high), 2.1 (medium/replacement level) and 1.6 (low).
Look at the population curves for these three fertility rates until 2150 in the diagram below. Label the
curves on the diagram with the fertility rates from the above paragraph.

The status of women
Women are the key to reducing the population, but all too often they conceive against their wishes.
Read the following article from the UNFPA.
17. Highlight or underline issues which maintain the low status of women in one colour and
highlight or underline proposals which might lead to a lowering of fertility rate, in another
colour.
The Declaration and Programme of Action of the World Summit for Social Development, held
in Copenhagen in March 1995, called for equal educational and work opportunities for women.
The Platform of Action of the Fourth World Conference on Women held in Beijing in September
1995 also called for universal access to quality health services by 2015; equal land, credit and
employment access to women; the establishment of effective personal and political rights; and the
education of girls and young women as the key intervention for the empowerment of women. In
1997, the United Nations High Commissioner for Human Rights reiterated that women's rights are
fundamental human rights. Women's social status and access to education, employment and health
care are loosely linked to economic development. Women in many countries still lack the right to
own land, to inherit property or to have access to credit; girls are denied schooling; female workers
routinely face job discrimination; and women’s sexual and reproductive health needs are widely
neglected.
Women often face legal and institutional barriers to economic activity outside the home, including
laws or customs that deny them the right to own land, inherit property, establish credit or move up in
their field of work. Within the home, women with families usually have the primary responsibility for
child care as well as carrying water; collecting fuel; growing, processing and cooking food, often in
addition to their paid employment.
Enhancement of their productive roles is especially important for women whose status in society
has been dependent solely on their reproductive capabilities. In the absence of other sources of
status, a woman's ability to decide about a marriage partner or family size is limited. This is true for
women in all countries.
Education is a critical ingredient in the empowerment process. Of the 960 million illiterate adults in
the world, two thirds are female. The ICPD Programme of Action calls for universal enrolment in
primary school by the year 2015, a time line influenced by the magnitude of the task. Despite
progress in expanding access to primary education throughout the world, an estimated 130 million
children - including 90 million girls - are not enrolled in primary school.7 And while enrolment in
primary and secondary school totals nearly 900 million children worldwide, there are about 85
million fewer girls than boys enrolled. For adult women, educational attainment is highest in
developed countries where, except for Eastern and Southern Europe, women have an average of
10 years of education or more. In Africa, women have an average of less than one year of formal
education.
The level of education achieved by a woman is also strongly associated with both lower infant
mortality and lower fertility. In poorer countries, where access to health care is often limited, each
additional year of schooling is associated with a 5 to 10 per cent decline in child deaths. And the

impact of a woman's educational attainment on family size is second only to that of access to family
planning services. In combination, high levels of education and access to family planning services
translate into both lower infant mortality and lower fertility. In Sri Lanka and the Republic of Korea,
where women have an average of more than six years of schooling, infant mortality rates are among
the lowest in Asia and families have, on average, about two children.
Gender discrimination often begins long before a girl enters school. Deep-rooted traditions of son
preference can result in both passive and active neglect. A girl may be given less food than her
brothers, be less likely to see a doctor when ill or be prevented from attending school in order to
help with household chores and child care. Access to new technologies is compounding the
problem of son preference in some countries, where sex-selective abortion is a growing problem.
Female genital mutilation is another gender- based tradition with severe negative consequences for
the health of girls and women.
Men's involvement
The ICPD Programme of Action recognizes that men, in most societies, exercise preponderant
power in nearly every sphere of life, ranging from personal decisions regarding the size of families
to the policy and programme decisions taken at all levels of government. Achieving gender equality,
equity and women’s empowerment will require the support of men.
Men also must play an active role in stopping the abuse of their daughters, wives, mothers and
sisters by joining the effort to eradicate all forms of gender-based violence including domestic
violence, child prostitution and rape.
Encouragement of joint decision-making in the family and of male support for their partners' choices
related to reproduction is a vital component of an empowering and participatory approach to
reproductive health.
Family planning programmes traditionally focused primarily on women via maternal and child health
programmes. This approach generally neglected “male methods" of contraception - condoms,
vasectomy and withdrawal. It also placed responsibility for contraception decisions solely on women
and impeded efforts to promote male responsibility. It may even have deterred contraceptive use by
women, particularly in cultures where men dominate reproductive decision-making. (Where partners
disagree on the number of children or the use of contraceptives, the man's views will usually
prevail.)
Studies show that men are more favourable to family planning than has been widely assumed, but
these attitudes must be translated into support and cooperation in decision-making. The
development and use of male methods of contraception, which are safe, effective, reversible and
acceptable, would expand the options for both men and women, attract additional users and
improve reproductive health. Male cooperation and responsible sexual behaviour will be required to
counter the AIDS pandemic and rising STD rates, since the male condom is the most widely
available barrier to disease transmission. Men also need to be educated on the implications of their
sexual behaviour for their partners' health.
The following are among suggested options that reproductive health programmes may use to
increase male involvement:
● Inform men about family planning and reproductive health
● Encourage joint decision-making by spouses

● Provide contraceptive choices
● Design convenient, appealing services
Female Genital Mutilation
Female genital mutilation is a major public health issue: an estimated 130 million women worldwide
have undergone some form of the procedure. It is practised in one form or another in around 40
countries mostly in East and West Africa and parts of the Arabian Peninsula. As a result of migration
from these areas, it is now also practised in Europe and North America.
Each year it is estimated, that about 2 million or more girls are at risk of mutilation. The procedure is
usually performed on young girls or adolescents and sometimes when a woman has just given birth.
Because it is typically performed outside the medical system, without anaesthesia using unclean
instruments, it can have grave health consequences. The commonest type of female genital
mutilation is excision of the clitoris and the labia minora, accounting for up to 80 per cent of all
cases. The most extreme is infibulation, which constitutes about 15 per cent of all procedures.
The ICPD was the first international conference to speak out plainly against it, calling on the
international community to eliminate the practice, which it stressed, violates basic human rights and
constitutes a lifelong risk to women's health.
Visit www.unfpa.org for more information.
18. List four reasons why educating women will reduce fertility/birth rate.
Population pyramids
Population or age/sex pyramids (sometimes called population profiles) show the distribution of
individuals in a population. Look at the population pyramid below.
19. What kind of information does a population pyramid show?
20. Look at the bands indicated by the 3 arrows in the pyramid at
right. Describe the information / trend indicated by the bars
where each of the arrows is located.

Population pyramids can indicate political and social changes too: China used the concept of
optimum population to try to stabilise its population at 1.2 billion by the year 2000 and reduce the
population to a government set level of 700 million by the end of the century.
21. Annotate the above diagram to show social and political changes. Justify your response with
reasons, examples, and/or other evidence. You may use the space below.
There are four basic population pyramid shapes:
22. Complete the table below with the characteristics of each pyramid.
Stage early expansive late expansive stationary contractive
Birth rate
Death rate
Life
expectancy
Population
growth

Analysing population pyramids
Visit the website of the US Bureau of the Census, Centre of International Research, UNDIESA, at
www.census.gov and find the International Database. The following population pyramids, from the
US Bureau of the Census, show projections into the future for selected countries.
http://www.census.gov/ipc/www/idbpyr.html Look at this site as it has dynamic pyramids changing
over time.
23. For each pyramid below, identify the stage. You might like to look up your own country, if not
included, and do the same. Annotate pyramids with comments on the birth rate, fertility,
death rate, life expectancy, gender differences and any special events.
Pyramid 1: Afghanistan
Pyramid 2: Central African Republic
Pyramid 3: Italy
Pyramid 4: United Kingdom

Look up some more countries.
24. What is happening in countries with high levels of AIDS?
25. What is happening in MEDCs? China? India? Tanzania?
The Demographic Transition Model
Demographic transition is the pattern of decline in mortality and fertility (natality) of a country as a
result of social and economic development. Demographic transition can be described as a
four-stage population model, which can be linked to the stages of the sigmoid growth curve
(S-curve).
Source: http://www.bbc.co.uk/staticarchive/d01fbdc5be6461d6acb7af10d767706c7a704d9b.gif

The following diagram shows two demographic transitions.
26. For Country A, draw vertical lines on the graph to indicate the various phases of the
transition model.
27. For Country B, use a different color pen or pencil to draw vertical lines on the graph to
indicate the various phases of the transition model.
28. Provide evidence/data from the diagram to justify your placement of the vertical lines
showing the different stages of the demographic transition model.

ESS Topic 8.1 - Human population dynamics guide

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ESS Topic 8.1 - Human population dynamics guide