Human Population Growth
Global Population Trends
Current population > 8 billion; hit 8B in 2023.
Growth rate has slowed since 1960 to about per year.
Uneven geographic distribution: in 2015, 2% of births occurred in more-developed countries; 98% in less-developed countries.
Population change: (Births + Immigration minus Deaths + Emigration).
Population pyramids show age structure; large shares under 15 in many developing countries -> rapid growth potential.
Earth Overshoot Day & Footprint
Earth Overshoot Day reflects humanity consuming resources faster than the Earth can renew them.
Global footprint data indicate a current overshoot of about (based on Global Footprint Network data across 1971–2024).
Population Pyramids & Age Structure
Age structure = proportion of people in young, middle, and older age groups; distributions vary by country.
Countries with a large % under 15 tend to grow rapidly.
Malthusian Perspective
Core idea: Population, if unchecked, grows geometrically; resources grow linearly.
Outcome: overpopulation leads to resource scarcity and potential societal downfall.
Malthus’ view: population growth is main driver of environmental degradation due to scarcity; resources cannot keep up with demand.
Malthus’ Numbers
Population grows exponentially: P \propto a^{t}\, (a>1)
Resources grow linearly: R \propto bt\, (b>0)
Demographic Trends & Checks
Oscillations in population due to scarcity and resource conflict.
Preventative checks reduce birth rates; positive checks increase death rates.
Historical Background & Responses
Essay response linked to Godwin; discussed wages for the poor and wealth redistribution.
Engels linked enclosure movements to urban poverty and wealth concentration; noted automation and wealth accumulation amid scarcity.
Examining the Malthusian Perspective
Malthus argued solutions are within individual control; welfare may facilitate growth.
Emphasized moral restraint (notably by women) as a population check.
Critique: shifts blame away from political/economic systems and structural inequalities.
Should environmental concerns be addressed via population control?
Moral implications of fertility policies.
Historical examples: Romania (1960s–1990s); China’s one-child policy (with coercive/voluntary elements).
Policies to counter declining populations: cash incentives, tax breaks, paid parental leave in various countries.
Neo-Malthusians & Cornucopian Viewpoints
Neo-Malthusians (1940s–1970s): emphasize environmental limits; advocate birth control and population management.
Cornucopians: view populations as a resource; more people mean more innovation; technology can outpace limits.
Population, Development, & Environmental Impact
Ehrlich (1968) emphasized population as a driver of environmental pressure.
Schneider-Mayerson prompts discussion on views about family size in climate-era.
Environmental impacts depend on access, technology, and governance, not just total numbers.
Population & Innovation
Green Revolution (early 20th c. to 1960s): technology transfer, fertilizers, high-yield varieties increased food supply.
Induced intensification and Norman Borlaug’s work helped avert famines; Nobel Prize 1970.
Uncertainties remain about long-term sustainability of current agricultural intensification.
Cornucopian vs (Neo)Malthusian Perspectives on Food Security
Neo-Malthusians: more people cannot be fed without constraints; growth outpaces supply.
Cornucopians: more people spurring innovation; food production can keep up with demand.
Critiques of Cornucopianism
Benefits of tech are uneven and can harm ecosystems (e.g., aquatic systems).
More food produced is not always equitably distributed; risks of techno-utopianism.
Amartya Sen & Capabilities Approach
Scarcity is about access and capability, not just resource availability.
Historical famines (1981) show that famine can occur with food availability but poor access.
Still possible that resource scarcity could arise in the future.
Famine History & Data
From OurWorldInData data: famines since the 1860s with large mortality in India, China, the Soviet Union, and other regions.
Famine patterns reflect governance, conflict, and access as much as population pressures.
Demographic Transition Model (DTM)
A multi-stage model describing population growth through economic development.
Based on historical European patterns (1800–present).
Focuses on changes in birth and death rates across development stages.
DTM Stage 1: Pre-industrial
High death rate and high birth rate; stable population; no countries currently in Stage 1.
DTM Stage 2
Rapid fall in death rate due to health and child-survival gains; birth rate remains high; rapid population growth.
DTM Stage 3
Death rate continues to fall; birth rate declines due to female education, contraception access; population growth slows.
DTM Stage 4
Both birth and death rates low and stable; population stable (e.g., USA).
DTM Stage 5
Birth rates continue to fall; death rates may rise with aging population; possible population decline.
Critiques of the DTM
Assumes a linear, European-centric development path.
Ignores non-economic drivers of population change.
What Influences Population Change?
Population change = (Births + Immigration) − (Deaths + Emigration).
Replacement-level fertility ≈ children per couple (slightly above 2 due to mortality).
Total fertility rate: average number of children a woman would bear during her reproductive years.
Factors that Affect Fertility
1) Importance of children as labor;
2) Cost of raising/educating children;
3) Availability of social support infrastructure (healthcare, pensions);
4) Education & employment for women;
5) Age at marriage;
6) Availability of birth control;
7) Religious beliefs, cultural norms.
Women’s Rights & Fertility
Kerala, India: slowing population growth linked to women’s empowerment, education, and literacy.
Kerala’s 1990s–2024 measures intend to strengthen women’s welfare and reproductive choice.
Globally, women's education and access to reproductive health care correlate with lower fertility rates.
Does education lead to lower fertility, or does lower fertility enable more education? Both are interlinked.
National Fertility & Female Literacy (Global Context)
Cross-country data (2008) show a general association: higher female literacy aligns with lower national fertility rates.
Population Growth & Environment: Global Patterns
More developed countries: ~17% of the world’s population; use ~70% of resources.
Less developed countries (LDCs): 80% of the world’s population; use ~30% of resources.
Ecological Footprints & Population
Less-developed countries have higher population growth rates but lower per-capita emissions.
Nearly inverse relationship between population growth and per-capita CO2 emissions.
CO2 Emissions by Population Group (Global Context)
CO2 per capita in 2017 shown in ranges from <0 to >50 tonnes/year, with regional variations.
Data sources: Our World in Data, CDIAC, Global Carbon Project.
Population, Resources, & Development Intersections
Cornucopian vs Malthusian debate centers on whether technology and innovation can outpace resource limits.
Amartya Sen’s capabilities approach emphasizes access/agency over simple resource totals.