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.

http://www.unfpa.org/

http://www.unfpa.org/


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

http://www.census.gov/

http://www.census.gov/

http://www.census.gov/ipc/www/idbpyr.html

http://www.census.gov/ipc/www/idbpyr.html


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

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

Education

Transcript of ESS Topic 8.1 - Human population dynamics guide