The study of human populations and their impact on the natural world is called

A population describes a group of individuals of the same species occupying a specific area at a specific time. Some characteristics of populations that are of interest to biologists include the population density , the birthrate , and the death rate . If there is immigration into the population, or emigration out of it, then the immigration rate and emigration rate are also of interest. Together, these population parameters, or characteristics, describe how the population density changes over time.

Demography is the study of the statistical characteristics of human populations, e.g. total size, age and sex composition ad changes over time with variations in birth and death rates.

In this unit we will measure population density, look at various population models.

​This unit is a minimum of 5 hours.

Significant Ideas:

• A variety of models and indicators are employed to quantify human population dynamics
• Human population growth rates are impacted by a complex range of changing factors.

Big questions:

• What strengths and weaknesses of the systems approach and the use of models have been revealed through this topic?
• To what extent have the solutions emerging from this topic been directed at preventing environmental impacts, limiting the extent of the environmental impacts, or restoring systems in which environmental impacts have already occurred?
• What value systems can you identify at play in the causes and approaches to resolving the issues addressed in this topic?
• How does your own value system compare with others you have encountered in the context of issues raised in this topic?
• How are the issues addressed in this topic of relevance to sustainability or sustainable development?
• In what ways might the solutions explored in this topic alter your predictions for the state of human societies and the biosphere some decades from now?
• How do models help our understanding of human dynamics?
• To what extent have population policies been effective in their aims?
• How do environmental value systems affect population dynamics? Give examples to support your answer.
• What are your views on these?
• Examine the relationship between population dynamics related to sustainable development.

Knowledge and understanding:

8.1.U1 Demographic tools for quantifying human population include crude birth rate (CBR) crude death rate (CDR), total fertility rate (TFR), doubling time (DT) and natural increase rate (NIR)
[Strengths and weaknesses of the use of a fossil fuel, of a renewable source of energy, and of nuclear power should be considered.]

• Define CBR, CDR, TFR, DT, and NIR
• Calculate values of CBR, CDR, TFR, DT, and NIR
• Explain why crude birth rate (CBR), crude death rate (CDR), total fertility rate (TFR), doubling time (DT) and natural increase rate (NIR) vary so much between countries
  

Birth rates:

• CBR- Crude birth rate is the number of live births per 1000 people in a population. 
• Total number of births/total population X 1000 = CBR.
• CBR does not calculate the age and sex structure of the population.

Fertility:

• TFR- Total fertility rate is the average number of births per woman of child-bearing age.

GFR- General fertility rate is the number of births per thousand woman aged between 15-49 years old.

ASBR- Age-specific birth rate is the number of births per 1000 women of any specific year group.

Doubling times:

• This is the time it takes for a population to double in size. 
• Doubling time=70/percentage growth rate.

Death rates:

• CDR- Crude death rate is the number of deaths per thousand people in population.
• It is a poor indicator as populations with many old people (MEDCs) have higher CDRs than countries with more younger populations. (Ex: Denmark 11% and Mexico 5%)
•  CDR= number of deaths/total population X 1000.

ASMR- Age-specific mortality rates is the number of deaths per 1000 women of any age group.

• ASMR= number of deaths/1000 women of any specific age group.

IMR- Infant mortality rates is the number of deaths  of children under 1 years old per 1000 live births.

Natural Increase:

• NIR- Natural increase rate is the CDR from the CBR. 
• CBR-CDR=NIR. This excludes migration.
• A NIR of 1% will make a double of a population in 70 years. The doubling time is 70 divided by the NIR.

8.1.U2 Global human population has followed a rapid growth curve, but there is uncertainty as to how this may be changing.

• Outline human population growth over time.
• Discuss the use of models in predicting growth of human populations.
• Discuss the nature of changes in the global human population, both past trends and future projections.
  

Exponential growth or geometric growth is when the population is growing, and there are no limiting factors slowing the growth. The impacts of exponential growth are huge amount of extra resources needed to feed, house, clothe and look after the increasing number of people. 

The world’s population is increasing very fast, this is due to many factors such as education, health, poverty, place of residence, and social class. Population growth is more common in Less economically developed countries ( LEDCs ) as they are less educated, and believe they need more children to help them make a living and take care of them in the future. Around 95% of population growth is happening in the LEDCs.

Governments have tried to reduce the population growth rate by proving health care as well as education and through policies e.g. China: One-child policy

More economically developed countries (MEDCs) believe they cannot raise children with a low income which means they only have children if it does not affect their standard of living. This shows us one more time that reducing birth rates in LEDCs can only be done by improving the standard of living in those countries.

8.1.U3 As human population grows, increased stress is placed on all of the Earth's systems.

• Explain the implications for Earth’s systems of the continued growth of the human population.

Like all living organisms, humans exploit their surroundings for resources. Before the beginning of agriculture about 10,000 years ago, small groups of humans wandered across large areas, hunting and gathering just enough food to stay alive. Population numbers were kept low because of the difficulty of finding food.

Fossil Fuels
The burning of fossil fuels leads to an increase in sulfur dioxide in the atmosphere, which causes acid rain. Acid rain has devastating consequences on biodiversity as many plants and animal species cannot survive these conditions. As the rain becomes more acidic, biodiversity decreases.
Sewage

If untreated sewage is released into rivers it provides food for bacteria, which will increase in numbers and use up the oxygen supply of the water. This results in a decrease in species diversity since only species that can live in areas with low oxygen concentrations will survive.

Deforestation

This can result in habitat destruction, a reduction in soil fertility and poor soil structure leading to a decrease in biodiversity.

Desertification

This decreases biodiversity as only species that can survive in a dry habitat will remain in these areas.

Grazing

At low grazing intensities the biodiversity of grassland is low because a few species of plants such as grasses are able to out-compete the others and dominate the ecosystem. As the grazing intensity increases the biodiversity increases as the dominant plant species are kept in check by grazers and the weaker competitors are therefore also able to grow. At very high grazing intensities the biodiversity decreases because only plants with adaptations to tolerate the effects of grazing are able to survive.

Pesticides

Pesticides can have adverse effects on the environment if they are not biodegradable and they can accumulate in the bodies of organisms over time. Due to the animals at each level in a food chain eating large numbers of the organisms from the level below in the food chain, the concentration of pesticide in the bodies of organisms increases at higher levels of food chains. This can result in the toxicity of the pollutant reaching fatal levels in the organisms at the top of the food chain.

image from https://www.researchgate.net

8.1.U4 Age-gender pyramids and demographic transition models (DTM) can be used in the prediction of human population growth. The DTM is a model that shows how a population transitions from a pre-industrial stage with high CBRs and CDRs to an economically advanced stage with low or declining CBRs and low CDRs.
[A variety of predictive models could be included, such as computer simulations, statistical and/or demographic tables for LEDCs and MEDCs, age–gender pyramids, and graphical extrapolation of population curves.]

• Construct and analyze age-gender pyramids
• Outline the stages of the demographic transition model.
  
• Use age-gender pyramids to place a society in a demographic transition stage.
  
• Use diagrams of the demographic transition model to determine CBR, CDR, and NIR.
  

The shapes of the pyramids are following:

• Expanding (stage 1) – high birth rates; rapid fall in each upward age group due to high death rates; short life expectancy.
  
• Expanding (stage 2) – high birth rates; fall in death rates as more living to middle age; slightly longer life expectancy. 
  
• Stationary (stage 3) – declining birth rate; low death rate’ more people living to old age. 
  
• Contracting (stage 4) – low birth rate; low death rate; higher dependency ratio; longer life expectancy. 
  

image from http://geographyfieldwork.com/

DTM- Demographic transition model shows us that countries progress through recognized stages in the transition from LEDC to MEDC. It suggests that death rates fall before birth rates and that the total population expands

While many of the more economically developed countries (MEDCs) have a declining population size, that of many of the less economically developed countries (LEDCs) is rising rapidly. The position of various countries on the demographic transition model reflects their development stages.

8.1.U5 Influences on human population dynamics include cultural, historical, religious, social, political and economic factors.

• Discuss how cultural, historical, religious, social, political, and economic factors can influence population dynamics.​

• Some agriculture cultures see that having more children help with working the land. While other cultures where women are employed and education have low birth rates.
• Religious believes include family planning. Most religions are pro-natalists.
• Social pressures are put on many women in more traditional societies to have children
• Governments may be pro-natalist or anti-natalists
• Availability of clean water, sanitation, adequate housing, reliable food supply, diseases, healthcare, occupation, civil conflicts

8.1.U6 National and international development policies may also have an impact on human population dynamics.

• Compare and evaluate two anti-natalist national population policies.
• Using an example, outline the factors that would lead a society to have pro-natalist policies, then outline and evaluate those policies
  
• Outline how the millennium development goals can play a role in reducing population growth.
  

​Many policy factors influence human population growth. Domestic and international development policies (which target the death rate through agricultural development, improved public health and sanitation, and better service infrastructure) may stimulate rapid population growth by lowering mortality without significantly affecting fertility.

Some analysts believe that birth rates will come down by themselves as economic welfare improves and that the population problem is therefore better solved through policies to stimulate economic growth.

Policies that reduce population growth rate:

• Pension schemes reduce parents reliance on their children for care when they are elderly.
• Taxes and poor job security can lead to a decision to have a smaller family.
• Any policy that stimulates economic growth usually leads to increased education and therefore knowledge of birth control.
• Urbanisation limits physical space to have large family.
• Policies directed at educating and liberating women.

Policies that increase population growth rate:

• Agricultural development, improved public health and sanitation etc. may lower CDR and stimulate rapid growth without lowering fertility (stage 2 of DTM)
• Lowering income tax or giving incentives and free education may increase CBR. E.g. Australian baby bonus
• Encourage immigration, particularly of workers. Especially if immigration is from less developed countries.

Millennium Development Goal 2: “Ensure that, by 2015, children everywhere, boys and girls alike, will be able to complete a full course of primary schooling”.

As soon as a government introduces free compulsory primary education the birth rates can decline. Free education alone does not have the same impact as many parents  children as free labor over educating them. If however primary school is free and compulsory then more children will attend and they cease to be an economic asset.

Application and Skills

8.1.A1 Calculate values of CBR, CDR, TFR, DT and NIR

​Birth rates:

• CBR- Crude birth rate is the number of live births per 1000 people in a population. 
• Total number of births/total population X 1000 = CBR.
• CBR does not calculate the age and sex structure of the population.

Fertility:

• TFR- Total fertility rate is the average number of births per woman of child-bearing age.

Doubling times:

• DT time it takes for a population to double in size. 
• DT=70/percentage growth rate.

Death rates:

• CDR- Crude death rate is the number of deaths per thousand people in population.
• It is a poor indicator as populations with many old people (MEDCs) have higher CDRs than countries with more younger populations. (Ex: Denmark 11% and Mexico 5%)
•  CDR= number of deaths/total population X 1000.

Natural Increase:

• NIR- Natural increase rate is the CDR from the CBR. 
• CBR-CDR=NIR. This excludes migration.
• A NIR of 1% will make a double of a population in 70 years. The doubling time is 70 divided by the NIR.

8.1.A2 Explain the relative values of CBR, CDR, TFR, DT and NIR

​Higher young = lower death rate
Social class - more poor people, higher death rate
Occupation - some hazardous 
Place of residence - urban = higher death rate

The NIR was 1.3 % during the first decade of the 21st century, hit its all-time high of 2.2 % in 1963, slowly fell throughout the latter part of the century, and has declined sharply during the past decade.  Although the NIR is lower now than in the 1960’s, the number of people being added to the population is still larger because there is a larger base number to multiply the percentage with.  Virtually 100% of the natural increase is located in LDC’s, primarily sub-Saharan Africa.  The TFR has dropped dramatically in MDC’s, normally hovering around 2, and has exceeded 6 in some African countries.  Just as the NIR, TFR, CBR, and CDR, the IMR is also highest in LDC’s, again primarily in Sub-Saharan Africa.  Only life expectancy and doubling time are higher in MDC’s.

8.1.A2 Analyse age-gender pyramids and diagrams showing demographic transition models.

Population pyramids are structures which show any measurable characteristic of the population; like sex, age, language, religion and occupation.

• a wide base indicates a high birth rate
• narrowing base suggests falling birth rate
• straight or near vertical sides reveal a low death rate
• concave slopes characterize high death rates
• bulges in the slope indicate immigration or in-migration
• deficits in the slope indicate emigration or out-migration or age-specific or sex-specific deaths (epidemics, war)

8.1.A4 Discuss the use of models in predicting the growth of human populations.

• Discuss the uncertainties associated with projecting human population growth

This might include computer simulations, statistical and/or demographic tables for LEDCs and MEDCs, age/sex pyramids and graphical extrapolation of population curves..

Many factors affect population growth. National or regional change in population count migration whereas a global population change does not even consider migration.

Factors influencing birth rates include: population age-structure, women status, type of economy, wealth, religion, social pressure, educational status, availability of contraceptives, desire for children, and the need for governmental policies such as child benefits. It is very difficult to predict the populations birth rate changes in all of these factors.

Death rate is influenced by: age-structure of the population, availability of clean water, sanitation, adequate housing, reliable food supply, prevalence of disease, provision of healthcare facilities, type of occupation, natural hazards, civil conflict/war, and chance factors. This is also difficult to predict changes for as there is too many factors.

Changing projections:

It has always been predicted that the world was not going to have enough food supply for everyone since the late 1700′s. In the 1990′s there were warnings about having a population explosion. It has been predicted that the population over 60 will increase and that the working population will have to work harder to keep the elderly alive, unless there is something done about it.

This has been discussed between academics and politicians. They keep coming to these 3 conclusions:

1. Those who think this is all just a scare story which can be changed/fixed with some changes to the retirement ages and pension policies.
2. Those who preach and doom, (poverty in old age, healthcare rationing, intergenerational warfare as young/old fight for scarce resources)
3. Those in between 1+2 who try and come up with reasonable ideas to reduce the impact of global greying.

Biggest part of the solution lies in:

1. expanding the shrinking population of workers by increasing retirement age and persuading women to work.
   
2. increasing productivity of the labour force.
   
3. persuading people to save more for their retirement.

8.1.A5 Explain the nature and implications of growth in human populations

The human population is growing exponentially using much of the the Earth’s finite resources, such as fossil fuels and minerals. As a result, the amount of waste and pollution is also on the rise. Certain living organisms act as indicator species, and their presence or absence shows the level of pollution in the air or water. Human populations are in the form of a ​J-curve currently peaking at 9 billion. Due to the increased population large amounts of resources needed to fuel population growth.

8.1.A6 Analyse the impact that national and international development policies can have on human population dynamics and growth
[Development policies may increase or decrease population growth:

• CBRs and growth rates are reduced through educating of women for greater independence (economic and reproductive), stimulation of economic growth to improve economic welfare and give greater economic independence, mechanization of the agricultural sector and subsequent urbanization.
• Growth rates may increase if CDRs fall as a result of improved public health, sanitation, and service infrastructure.]

Pro-natalist and anti-natalist policies

• Pro-natalist policies are policies which are designed with the purpose of increasing the birth rate/fertility rate of an area. They are found in countries with either very slow natural increase or natural decrease and in areas with aging populations.
• ​Anti-natalist policies aim to do the reverse: to encourage people to plan smaller families, lower fertility rates and reduce the number of births. These tend to be found in countries with high birth rates and rapidly growing populations.

Many areas of Europe have a low fertility rate because of the following reasons: education. In 1939, the French passed the “Code de la famille”, a complex piece of pro natalist legislation. ​The pro natalist methods in the policy included:

• Offering cash incentives to mothers who stayed at home to care for children.
• Subsidizing holidays.
• Banning the sale of contraceptives (repealed in 1967).

China instilled an anti natalist policy to help combat population explosion. Imbalances between population and available resources were steadily increasing. China has 7% of the world’s agricultural land and 23% of the world’s population.
The idea was to encourage economic development and improve the standard of living for the population.

• 1953 - First modern census takes place in China. The population comes in as 583 million.
• Between 1953 and 1964 the population increased by 112 million as Mao Zedong encouraged larger families in an attempt to make China stronger.
• Attempts to slow down population growth were started in the 1970s using the slogan “Later, longer, fewer”. People were encouraged to limit families to two children.
• 1979 - One child policy introduced.

8.1.A7 Discuss the cultural, historical, religious, social, political and economic factors that influence human population dynamics.

• Some agriculture cultures see that having more children help with working the land. While other cultures where women are employed and education have low birth rates.
• Religious believes include family planning. Most religions are pro-natalists.
• Social pressures are put on many women in more traditional societies to have children
• Governments may be pro-natalist or anti-natalists
• Availability of clean water, sanitation, adequate housing, reliable food supply, diseases, healthcare, occupation, civil conflicts

Key Terms

While many of the more economically developed countries (MEDCs) have a declining population size, that of many of the less economically developed countries (LEDCs) isrising rapidly. The position of various countries on the demographic transition model reflects their development stages.

Powerpoint and Notes Adapted from Brad Kremer

​​​​​​​​​Correct use of terminology is a key skill in ESS. It is essential to use key terms correctly when communicating your understanding, particularly in assessments. Use the quizlet flashcards or other tools such as learn, scatter, space race, speller and test to help you master the vocabulary.

International-mindness:

• A country's development depends on its economy and its demographics. It also depends on the policies of other countries and international organizations such as the World Bank the International Monetary Fund (IMF) and the World Trade Organization (WTO).

TOK

• A variety of models and indicators are employed to quantify human population dynamics-to what extent are the methods of the human sciences "scientific"?

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