Chapter 8: Human Population
Global Population Overview
World population is around 7.3 billion now; growth is concentrated in poorer nations. India is projected to become the most populous country, surpassing China due in part to less stringent population controls in India.
Current global population growth rate: about 88 million people per year, which is roughly 2.8 people every second. Population crossed 1 billion only after 1800; a new billion is added about every 12 years.
This pattern illustrates exponential growth, where even a small percentage increase yields large absolute gains because the base population is large.
Exponential Growth and Doubling Time
Exponential growth: a small percentage growth rate can produce large increases due to the large base population.
Doubling time can be estimated with the rule of 70: the doubling time is approximately
ext{Doubling time} \approx \frac{70}{r}
where r is the annual growth rate expressed as a percent.Global doubling time at about 1.2% per year:
\text{Doubling time} = \frac{70}{1.2} \approx 58 \text{ years}.Prior to the one-child policy, China’s doubling time was about 25 years (70/2.8%).
Why Is Population Growth a Problem?
Improvements in sanitation, medicine, and agriculture have reduced infant mortality, which is a good thing.
Despite lower infant mortality, rapid population growth can stress resources, social systems, and the environment when per-capita resource use is high or where technology and institutions do not keep pace.
Historical Perspectives: Malthus and Neo-Malthusians
Before the industrial revolution, high birth rates were seen as positive (more children to support parents in old age; larger labor pool for factories).
Thomas Malthus warned that population size could outstrip food supply.
Paul and Anne Ehrlich (Stanford) are considered neo-Malthusians because they have issued warnings about limits to growth.
Modern Trends and Impacts
Despite a quadrupling of the human population, predictions of imminent collapse have not materialized; food production has intensified.
Enhanced prosperity, education, and gender equity have contributed to slower birth rates.
Nonetheless, population growth continues to deplete resources, place stress on social systems, and degrade the environment.
Population Is Only One Environmental Factor (IPAT Model)
IPAT framework expresses environmental impact (I) as a function of population (P), affluence (A), and technology (T):
I = P \times A \times TA sensitivity factor S can be added to reflect vulnerability of a given environment:
I = P \times A \times T \times SHow each component affects impact:
Population (P): more people means more demand on space, resources, and waste production.
Affluence (A): higher per-capita consumption raises demand for resources.
Technology (T): can increase impact by enabling resource exploitation or decrease impact by improving efficiency.
After World War II, the combination of population growth, rising affluence, and technology led to a period of rapid environmental impact known as the Great Acceleration.
Technology and Environmental Impact (Examples)
Consider whether a given technology increases or decreases impact:
Oil drilling: often increases impact due to resource extraction and pollution.
Internet: can reduce impact by enabling efficiency and dematerialization of services.
Genetically Modified Organisms (GMOs): mixed impacts; can increase yield with lower inputs or raise other ecological concerns.
Demography: Studying Human Populations
Demography is the study of statistical changes in human populations (size, distribution, age structure, sex ratio, birth/death/emigration/immigration rates).
Even with technological capabilities to manage growth, basic population ecology and logistic growth suggest limits to continued growth in the long term.
Population Distribution and Age Structure
Global distribution is clumped; highest densities in temperate, subtropical, and tropical climates.
Age structure diagrams (population pyramids) show the numbers of people in each age class; they are valuable for predicting future growth.
Population Pyramids and Life Stage Implications
Wide base pyramid indicates many pre-reproductive individuals → potential for rapid growth.
Even-aged distribution indicates a stable population.
A pyramid with more post-reproductive individuals indicates a shrinking population.
Nigeria’s young-age concentration suggests faster future growth than Canada’s age structure.
Median Age and Dependency
Global median age today is about 28; projected to be around 35 by 2050.
An aging population can strain social welfare programs as fewer young workers support more elderly, especially in developed countries.
Sex Ratios
Natural birth sex ratio is approximately 106 males for every 100 females.
In China, the sex ratio has become skewed due to cultural preferences for male children and the one-child policy; ultrasounds and selective termination contribute to more male births (roughly 116 boys per 100 girls).
Immigration and Emigration
Population changes also occur through migration: immigration adds to a country’s population; emigration removes.
People migrate for economic opportunities, conflict, or environmental degradation.
Immigration/emigration significantly shape national population profiles (Table 8.2 shows net migration rates for various nations; examples: Spain 7.8, Canada 5.7, United States 3.9, Germany 1.5, China -0.4, Mexico -1.8, Turkey -4.5, El Salvador -8.0, Lebanon -20.3; Japan data not fully shown).
Infant Mortality and Industrialization
Infant mortality has declined with industrialization, improved food, and healthcare.
Example: China’s infant mortality rate dropped from 47 per 1,000 live births in 1980 to 16 per 1,000 in 2013.
Fertility and the Total Fertility Rate (TFR)
Total fertility rate (TFR) = average number of children born per woman over a lifetime.
Replacement fertility is about 2.1 for humans; this level keeps population stable in the absence of migration.
Industrialization, women’s rights, and healthcare have lowered TFR in many nations; nearly all European nations have a TFR below replacement.
By 2015, about 84 countries had fallen below replacement fertility; Europe’s natural increase (births minus deaths) was between 0.0% and 0.1%.
Demographic Transition Model (DTM)
The DTM describes economic and cultural changes that accompany industrialization, affecting birth and death rates.
Stages:
Pre-industrial: high death rates due to disease, poor healthcare, unstable food; birth rates remain high; population growth is generally stable.
Transitional: death rates fall thanks to better food and health care; birth rates stay high; rapid population growth.
Industrial: birth rates fall as women gain education/work opportunities and birth control becomes more accessible; population growth slows.
Post-industrial: population growth stabilizes or declines; countries like the United States are in this stage, though immigration can temporarily raise birth rates.
Universality and Fatigue in the Demographic Transition
The transition has occurred in many developed countries (Europe, Canada, US, Japan, etc.).
Some developing countries face demographic fatigue and may not complete the transition due to high populations and health challenges, especially in sub-Saharan Africa.
Will China and India Complete the Demographic Transition?
Both countries are in intermediate stages; India may overtake China due to less aggressive population controls.
The trajectory shows China and India moving through the transition at different paces, with India likely to accumulate more people if policies remain less restrictive.
Population and Society: Determinants of Fertility
Several economic and societal factors influence fertility:
Access to contraceptives
Acceptance of contraception use
Women’s rights and empowerment
Cultural influences
Level of affluence and poverty levels
Importance of child labor in the economy
Government support for retirees
Family Planning and Its Effects
Family planning aims to plan number and spacing of children; birth control includes measures to reduce pregnancy frequency.
Programs often provide free or subsidized services; usage rates vary: about 84% in China and the UK vs. less than 10% in some African nations.
Bangladesh’s family-planning program dramatically lowered TFR from about 7.0 to 2.3 by increasing contraception access and reproductive counseling.
Empowering Women and Fertility
Greater gender equality in decision-making, education, and job opportunities lowers fertility rates.
Equal rights allow women to make reproductive choices, contributing to lower fertility and better child care outcomes.
Economic Wealth and Population Growth
Increasing affluence generally lowers fertility rates; poverty tends to be associated with higher fertility and can drive environmental degradation.
Positive feedback loops exist where poverty leads to degradation and resource scarcity, which in turn fosters further poverty unless mitigated by education and development.
A simplified depiction: Poverty → Environmental Degradation → Resource Depletion → Carrying Capacity → Population → Poverty, with education acting to break the loop.
IPAT Revisited: Wealth and Environmental Impact
Expanding wealth can escalate environmental impacts when consumption outpaces sustainability; however, wealth can also enable better technology and infrastructure to reduce impact.
A striking comparison used: the ecological footprint of a person in a wealthy country can be many times higher than that of a person in a developing country (e.g., one person in the United States can have a similar or greater impact than several people in other nations, depending on consumption patterns).
Global footprint vs biocapacity: if I > B, there is an ecological deficit; if I < B, an ecological reserve.
The floor remains: reducing population growth and improving efficiency are key levers to reduce impact.
Sustainable Development Goals (SDGs) and Population
Population-focused development is aligned with the UN’s SDGs, which emphasize a bottom-up approach addressing poverty and social needs before imposing top-down birth-control measures.
There is no one-size-fits-all solution; policies must be tailored to each nation’s context.
SDGs framework includes a holistic set of goals spanning people, planet, prosperity, peace, and partnerships.
SDG Framework and Illustrative Goals (Summary)
People: End poverty and hunger in all forms; dignity and equality for all.
Planet: Protect natural resources and climate for future generations.
Prosperity: Ensure inclusive, sustainable economic growth and opportunities.
Peace and Partnerships: Foster peaceful, just, and inclusive societies; implement the agenda through global partnerships.
Example Sustainable Development Goals (selected):
Goal 3: Good Health and Well-being
Goal 1: No Poverty
Goal 2: Zero Hunger
Goal 4: Quality Education
Goal 5: Gender Equality
Goal 6: Clean Water and Sanitation
Goal 7: Affordable and Clean Energy
Goal 8: Decent Work and Economic Growth
Goal 9: Industry, Innovation, and Infrastructure
Goal 10: Reduced Inequalities
Goal 11: Sustainable Cities and Communities
Goal 12: Responsible Consumption and Production
Goal 13: Climate Action
Goal 14: Life Below Water
Goal 15: Life On Land
Goal 16: Peace, Justice, and Strong Institutions
Goal 17: Partnerships for the Goals
Gender Equality and COVID-19 Impacts (Recent Context)
Pre-COVID statistics (Goals for gender equality):
About 25% of national parliaments and 36% of local government representation by women (pre-COVID).
COVID-19 implications for gender equality:
Lockdowns have increased risk of violence against women and girls; women are on the front lines of health and social care.
Women accounted for about 70% of health and social workers.
Women bear additional household burdens during the pandemic.
Women spend roughly three times as many hours on unpaid domestic and care work as men.
Many women face increased violence and reduced access to services during crises.
Review Questions (Key Concepts)
Growth pattern question:
The human population is experiencing an exponential growth trend (not linear, logistic, or negative).
IPAT model question: which change would reduce environmental impact?
A decrease in population growth rate would reduce I; technological advances that improve efficiency can also reduce I; increased affluence tends to increase I unless offset by efficiency; consuming resources in a more sensitive environment would increase, not decrease, impact.
Therefore, the most direct reduction is a decrease in population growth rate, with technology-driven efficiency as a secondary mechanism to lower impact.
Population pyramids:
A pyramid with a wide base indicates rapid growth (many pre-reproductive individuals).
A pyramid with a stable (even) age distribution indicates stability.
A pyramid with more post-reproductive individuals indicates shrinking growth.
Japan’s fertility context:
If Japan’s total fertility rate is 1.4, replacement level is about 2.1, so Japan is expected to experience shrinking population.
Demographic transition stage identification:
A country experiencing a decrease in death rates due to better food and health care, while birth rates remain high and growth is rapid, is in the Transitional stage of the demographic transition model.
Notes on Important Quantities and Formulas
Population (P), Affluence (A), Technology (T) in IPAT:
I = P \times A \times TWith vulnerability factor S:
I = P \times A \times T \times SReplacement fertility: approximately 2.1 for humans to maintain stable population in the absence of migration.
Global doubling time example: \text{Doubling time} \approx \frac{70}{r}\quad (r\text{ in percent per year}); with r = 1.2\%, doubling time ≈ 58 years.
Demographic transition stages (summary):
Pre-industrial: high death, high birth; stable growth.
Transitional: death rate falls; birth rate remains high; rapid growth.
Industrial: birth rate falls; growth slows.
Post-industrial: growth stabilizes or declines.
Demographic proxies:
Median age rising from ~28 today to ~35 by 2050.
Sex ratio at birth natural around 106 males per 100 females; skew in some countries due to policy or cultural preferences.
SDG structure: 17 goals spanning people, planet, prosperity, peace, and partnerships; emphasis on tailored, country-specific approaches.
Practical Takeaways for Exam Preparation
Understand why population growth was historically perceived as problematic and how modern developments have changed that dynamic, while still recognizing environmental pressures.
Be able to apply the IPAT framework to reason about environmental impact under changes to P, A, T, and optionally S.
Recognize the stages of the demographic transition and what demographic indicators (birth rate, death rate, age structure) look like in each stage.
Interpret population pyramids and explain what they imply about future growth or decline.
Explain how education, gender equality, and family planning influence fertility rates and population growth.
Be able to discuss the relationship between wealth, consumption, and environmental impact, including the concept of ecological deficit vs reserve.
Know the basic United Nations SDGs relevant to population and development, and why a bottom-up approach is often emphasized.
Be aware of contemporary gender issues highlighted by the COVID-19 pandemic, including impacts on women in health care, domestic labor, and violence risk.
Key equations to remember:
I = P \times A \times T
I = P \times A \times T \times S
\text{Doubling time} \approx \frac{70}{r}
\text{Replacement fertility} \approx 2.1
Population projections: current ≈ 7.3\times 10^9; by 2050 ≈ 9.7\times 10^9 (as cited in the slides).
Global Population Overview part 2
World population is around 7.3 billion now; growth is concentrated in poorer nations. India is projected to become the most populous country, surpassing China due in part to less stringent population controls in India.
Current global population growth rate: about 88 million people per year, which is roughly 2.8 people every second. Population crossed 1 billion only after 1800; a new billion is added about every 12 years.
This pattern illustrates exponential growth, where even a small percentage increase yields large absolute gains because the base population is large.
Exponential Growth and Doubling Time
The concept of exponential growth means a small percentage growth rate can produce large increases due to the large base population.
Doubling time can be estimated with the rule of 70.
Global doubling time at about 1.2% per year:
ext{Doubling time} = \frac{70}{1.2} \approx 58 \text{ years}.
Prior to the one-child policy, China’s doubling time was about 25 years (70/2.8%).
Why Is Population Growth a Problem?
Improvements in sanitation, medicine, and agriculture have reduced infant mortality, which is a good thing.
Despite lower infant mortality, rapid population growth can stress resources, social systems, and the environment when per-capita resource use is high or where technology and institutions do not keep pace.
Historical Perspectives: Malthus and Neo-Malthusians
Before the industrial revolution, high birth rates were seen as positive (more children to support parents in old age; larger labor pool for factories).
Thomas Malthus warned that population size could outstrip food supply.
Paul and Anne Ehrlich (Stanford) are considered neo-Malthusians due to their warnings about limits to growth.
Modern Trends and Impacts
Despite a quadrupling of the human population, predictions of imminent collapse have not materialized; food production has intensified.
Enhanced prosperity, education, and gender equity have contributed to slower birth rates.
Nonetheless, population growth continues to deplete resources, place stress on social systems, and degrade the environment.
Population Is Only One Environmental Factor (IPAT Model)
The IPAT framework expresses environmental impact (I) as a function of population (P), affluence (A), and technology (T):
I = P \times A \times T
A sensitivity factor S can be added to reflect the vulnerability of a given environment:
I = P \times A \times T \times S
How each component affects impact:
Population (P): more people means more demand on space, resources, and waste production.
Affluence (A): higher per-capita consumption raises demand for resources.
Technology (T): can increase impact by enabling resource exploitation or decrease impact by improving efficiency.
After World War II, the combination of population growth, rising affluence, and technology led to a period of rapid environmental impact known as the Great Acceleration.
Technology and Environmental Impact (Examples)
Consider whether a given technology increases or decreases impact:
Oil drilling: often increases impact due to resource extraction and pollution.
Internet: can reduce impact by enabling efficiency and dematerialization of services.
Genetically Modified Organisms (GMOs): mixed impacts; can increase yield with lower inputs or raise other ecological concerns.
Demography: Studying Human Populations
Demography involves the study of statistical changes in human populations (size, distribution, age structure, sex ratio, birth/death/emigration/immigration rates).
Even with technological capabilities to manage growth, basic population ecology and logistic growth suggest limits to continued growth in the long term.
Population Distribution and Age Structure
Global distribution is clumped; highest densities in temperate, subtropical, and tropical climates.
Age structure diagrams (population pyramids) visually represent the numbers of people in each age class, valuable for predicting future growth.
Population Pyramids and Life Stage Implications
A wide base pyramid indicates many pre-reproductive individuals, suggesting potential for rapid growth.
An even-aged distribution indicates a stable population.
A pyramid with more post-reproductive individuals indicates a shrinking population.
Nigeria’s young-age concentration suggests faster future growth than Canada’s age structure.
Median Age and Dependency
Global median age today is about 28; projected to be around 35 by 2050.
An aging population can strain social welfare programs as fewer young workers support more elderly, especially in developed countries.
Sex Ratios
The natural birth sex ratio is approximately 106 males for every 100 females.
In China, the sex ratio has become skewed due to cultural preferences for male children and the one-child policy; ultrasounds and selective termination contribute to more male births (roughly 116 boys per 100 girls).
Immigration and Emigration
Population changes also occur through migration: immigration adds to a country’s population; emigration removes.
People migrate for economic opportunities, conflict, or environmental degradation.
Immigration/emigration significantly shape national population profiles (Table 8.2 shows net migration rates for various nations; examples: Spain 7.8, Canada 5.7, United States 3.9, Germany 1.5, China -0.4, Mexico -1.8, Turkey -4.5, El Salvador -8.0, Lebanon -20.3; Japan data not fully shown).
Infant Mortality and Industrialization
Infant mortality has declined with industrialization, improved food, and healthcare.
Example: China’s infant mortality rate dropped from 47 per 1,000 live births in 1980 to 16 per 1,000 in 2013.
Fertility and the Total Fertility Rate (TFR)
The total fertility rate (TFR) is the average number of children born per woman over a lifetime.
Replacement fertility is about 2.1 for humans; this level keeps population stable in the absence of migration.
Industrialization, women’s rights, and healthcare have lowered TFR in many nations; nearly all European nations have a TFR below replacement.
By 2015, about 84 countries had fallen below replacement fertility; Europe’s natural increase (births minus deaths) was between 0.0% and 0.1%.
Demographic Transition Model (DTM)
The Demographic Transition Model (DTM) describes economic and cultural changes that accompany industrialization, affecting birth and death rates.
Stages:
Pre-industrial: high death rates due to disease, poor healthcare, unstable food; birth rates remain high; population growth is generally stable.
Transitional: death rates fall thanks to better food and health care; birth rates stay high; rapid population growth.
Industrial: birth rates fall as women gain education/work opportunities and birth control becomes more accessible; population growth slows.
Post-industrial: population growth stabilizes or declines; countries like the United States are in this stage, though immigration can temporarily raise birth rates.
Universality and Fatigue in the Demographic Transition
The transition has occurred in many developed countries (Europe, Canada, US, Japan, etc.).
Some developing countries face demographic fatigue and may not complete the transition due to high populations and health challenges, especially in sub-Saharan Africa.
Will China and India Complete the Demographic Transition?
Both countries are in intermediate stages; India may overtake China due to less aggressive population controls.
The trajectory shows China and India moving through the transition at different paces, with India likely to accumulate more people if policies remain less restrictive.
Population and Society: Determinants of Fertility
Several economic and societal factors influence fertility:
Access to contraceptives
Acceptance of contraception use
Women’s rights and empowerment
Cultural influences
Level of affluence and poverty levels
Importance of child labor in the economy
Government support for retirees
Family Planning and Its Effects
Family planning aims to plan the number and spacing of children; birth control includes measures to reduce pregnancy frequency.
Programs often provide free or subsidized services; usage rates vary: about 84% in China and the UK vs. less than 10% in some African nations.
Bangladesh’s family-planning program dramatically lowered TFR from about 7.0 to 2.3 by increasing contraception access and reproductive counseling.
Empowering Women and Fertility
Greater gender equality in decision-making, education, and job opportunities lowers fertility rates.
Equal rights allow women to make reproductive choices, contributing to lower fertility and better child care outcomes.
Economic Wealth and Population Growth
Increasing affluence generally lowers fertility rates; poverty tends to be associated with higher fertility and can drive environmental degradation.
Positive feedback loops exist where poverty leads to degradation and resource scarcity, which in turn fosters further poverty unless mitigated by education and development.
A simplified depiction: Poverty → Environmental Degradation → Resource Depletion → Carrying Capacity → Population → Poverty, with education acting to break the loop.
IPAT Revisited: Wealth and Environmental Impact
Expanding wealth can escalate environmental impacts when consumption outpaces sustainability; however, wealth can also enable better technology and infrastructure to reduce impact.
A striking comparison used: the ecological footprint of a person in a wealthy country can be many times higher than that of a person in a developing country (e.g., one person in the United States can have a similar or greater impact than several people in other nations, depending on consumption patterns).
Global footprint vs biocapacity: if I > B, there is an ecological deficit; if I < B, an ecological reserve.
The floor remains: reducing population growth and improving efficiency are key levers to reduce impact.
Sustainable Development Goals (SDGs) and Population
Population-focused development is aligned with the UN’s Sustainable Development Goals (SDGs), which emphasize a bottom-up approach addressing poverty and social needs before imposing top-down birth-control measures.
There is no one-size-fits-all solution; policies must be tailored to each nation’s context.
SDGs framework includes a holistic set of goals spanning people, planet, prosperity, peace, and partnerships.
SDG Framework and Illustrative Goals (Summary)
People: End poverty and hunger in all forms; dignity and equality for all.
Planet: Protect natural resources and climate for future generations.
Prosperity: Ensure inclusive, sustainable economic growth and opportunities.
Peace and Partnerships: Foster peaceful, just, and inclusive societies; implement the agenda through global partnerships.
Example Sustainable Development Goals (selected):
Goal 3: Good Health and Well-being
Goal 1: No Poverty
Goal 2: Zero Hunger
Goal 4: Quality Education
Goal 5: Gender Equality
Goal 6: Clean Water and Sanitation
Goal 7: Affordable and Clean Energy
Goal 8: Decent Work and Economic Growth
Goal 9: Industry, Innovation, and Infrastructure
Goal 10: Reduced Inequalities
Goal 11: Sustainable Cities and Communities
Goal 12: Responsible Consumption and Production
Goal 13: Climate Action
Goal 14: Life Below Water
Goal 15: Life On Land
Goal 16: Peace, Justice, and Strong Institutions
Goal 17: Partnerships for the Goals
Gender Equality and COVID-19 Impacts (Recent Context)
Pre-COVID statistics (Goals for gender equality):
About 25% of national parliaments and 36% of local government representation by women (pre-COVID).
COVID-19 implications for gender equality:
Lockdowns have increased risk of violence against women and girls; women are on the front lines of health and social care.
Women accounted for about 70% of health and social workers.
Women bear additional household burdens during the pandemic.
Women spend roughly three times as many hours on unpaid domestic and care work as men.
Many women face increased violence and reduced access to services during crises.
Review Questions (Key Concepts)
Growth pattern question:
The human population is experiencing an exponential growth trend (not linear, logistic, or negative).
IPAT model question: which change would reduce environmental impact?
A decrease in population growth rate would reduce I; technological advances that improve efficiency can also reduce I; increased affluence tends to increase I unless offset by efficiency; consuming resources in a more sensitive environment would increase, not decrease, impact.
Therefore, the most direct reduction is a decrease in population growth rate, with technology-driven efficiency as a secondary mechanism to lower impact.
Population pyramids:
A pyramid with a wide base indicates rapid growth (many pre-reproductive individuals).
A pyramid with a stable (even) age distribution indicates stability.
A pyramid with more post-reproductive individuals indicates shrinking growth.
Japan’s fertility context:
If Japan’s total fertility rate is 1.4, replacement level is about 2.1, so Japan is expected to experience shrinking population.
Demographic transition stage identification:
A country experiencing a decrease in death rates due to better food and health care, while birth rates remain high and growth is rapid, is in the Transitional stage of the demographic transition model.
Practical Takeaways for Exam Preparation
Understand why population growth was historically perceived as problematic and how modern developments have changed that dynamic, while still recognizing environmental pressures.
Be able to apply the IPAT framework to reason about environmental impact under changes to P, A, T, and optionally S.
Recognize the stages of the demographic transition and what demographic indicators (birth rate, death rate, age structure) look like in each stage.
Interpret population pyramids and explain what they imply about future growth or decline.
Explain how education, gender equality, and family planning influence fertility rates and population growth.
Be able to discuss the relationship between wealth, consumption, and environmental impact, including the concept of ecological deficit vs reserve.
Know the basic United Nations SDGs relevant to population and development, and why a bottom-up approach is often emphasized.
Be aware of contemporary gender issues highlighted by the COVID-19 pandemic, including impacts on women in health care, domestic labor, and violence risk.
Key Terms, Concepts, and Formulas
Exponential Growth: A growth pattern where a small percentage increase yields large absolute gains because the base population is large.
Doubling Time: The time it takes for a population to double. It can be estimated using the rule of 70.
Rule of 70 Formula: \text{Doubling time} \approx \frac{70}{r}, where r is the annual growth rate expressed as a percent. At a global growth rate of 1.2\% per year, the doubling time is approximately 58 years.
Neo-Malthusians: Descendants of Malthusian thought, like Paul and Anne Ehrlich, who issue warnings about limits to growth if population outstrips resources.
IPAT Framework: A model expressing environmental impact (I) as a function of Population (P), Affluence (A), and Technology (T).
Formula: I = P \times A \times T
With a sensitivity factor (S) reflecting environmental vulnerability: I = P \times A \times T \times S
Population (P): More people means more demand on space, resources, and waste production.
Affluence (A): Higher per-capita consumption raises demand for resources.
Technology (T): Can increase impact by enabling resource exploitation or decrease impact by improving efficiency.
Great Acceleration: A period after World War II marked by a rapid increase in environmental impact due to the combination of population growth, rising affluence, and technology.
Demography: The study of statistical changes in human populations, encompassing size, distribution, age structure, sex ratio, and birth/death/emigration/immigration rates.
Age Structure Diagrams (Population Pyramids): Visual representations showing the numbers of people in each age class, valuable for predicting future population growth or decline.
Wide Base Pyramid: Indicates many pre-reproductive individuals and potential for rapid future growth.
Even-aged Distribution: Suggests a stable population.
More Post-reproductive Individuals Pyramid: Indicates a shrinking population.
Aging Population: A population with a rising proportion of elderly individuals, often leading to strains on social welfare programs as fewer younger workers support more retirees.
Natural Birth Sex Ratio: Approximately 106 males for every 100 females at birth. (Can be skewed by cultural preferences or policies).
Immigration: The act of people moving into a country, adding to its population.
Emigration: The act of people moving out of a country, removing from its population.
Infant Mortality Rate: The rate of deaths of infants under one year of age per 1,000 live births, often declining with industrialization and improved healthcare.
Total Fertility Rate (TFR): The average number of children born per woman during her lifetime.
Replacement Fertility: The TFR required to keep a population size stable in the absence of migration, approximately 2.1 for humans.
Demographic Transition Model (DTM): Describes economic and cultural changes that influence birth and death rates as societies industrialize, typically moving through four stages:
Pre-industrial Stage: Characterized by high birth rates and high death rates, resulting in a relatively stable population.
Transitional Stage: Marked by falling death rates (due to improved food and healthcare) while birth rates remain high, leading to rapid population growth.
Industrial Stage: Birth rates begin to fall (due to factors like women's education and birth control access), causing population growth to slow.
Post-industrial Stage: Population growth stabilizes or declines, with birth rates often falling below death rates.
Demographic Fatigue: A state where developing countries face significant challenges in completing the demographic transition due to very high populations, limited resources, and persistent health issues.
Family Planning: Programs and services aimed at planning the number and spacing of children.
Birth Control: Any measures taken to reduce the frequency of pregnancy.
Ecological Footprint: A measure of human demand on the Earth's ecosystems, represented as the amount of biologically productive land and sea area required to provide the resources an individual or population consumes and to assimilate their waste.
Biocapacity: The capacity of a given biologically productive area to generate a continuous supply of renewable resources and to absorb its waste outputs.
Ecological Deficit: Occurs when the ecological footprint of a region or humanity exceeds its biocapacity (I > B).
Ecological Reserve: Occurs when the biocapacity of a region or humanity exceeds its ecological footprint (I < B).
Sustainable Development Goals (SDGs): A collection of 17 interlinked global goals designed by the United Nations in 2015 to be a "blueprint to achieve a better and more sustainable future for all." They address societal needs across people, planet, prosperity, peace, and partnerships.
Key Population Quantities:
Global population today: Approximately 7.3 billion.
Projected global population by 2050: Approximately 9.7 billion.
Global median age: Currently around 28, projected to be around 35 by 2050.