Announcements. Paul Ehrlich (Stanford Ecologist) Thomas Malthus (economist)

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1 Announcements First exam next Tuesday Bring a number two pencil (and a spare) Today: Human population growth End of lecture today: Exam review...democracy cannot survive overpopulation. Human dignity cannot survive it. Convenience and decency cannot survive it. As you put more and more people into the world, the value of life not only declines, it disappears. It doesn't matter if someone dies. The more people there are, the less one individual matters. Isaac Asimov Thomas Malthus (economist) 1798: Essay on the Principle of Population as it Affects the Future Improvement of Society Population growth tends to outstrip the means of subsistence Food increases arithmetically whereas population increases geometrically (exponentially) The poor can be kept alive by charity, but since they would then propagate, this is cruelty in disguise. Paul Ehrlich (Stanford Ecologist) 1968: The Population Bomb The battle to feed all of humanity is over. In the 1970s the world will undergo famines Hundreds of millions of people are going to starve to death 1

2 World population growth World population growth Human populations have increased at greater than exponential rates - Why? Has this lead to, humanitarian, economic and environmental disaster? What are the implications of this kind of human population growth? Review of population concepts Populations grow exponentially But, as populations approach carrying capacity, growth slows due to resource limitation, density-dependent mortality These phenomena can be quantified using exponential and logistic growth models Do human populations follow the same rules? Consequences of Exploding Populations (Brown 2009) Larger population with high rates of resource consumption deforestation groundwater depletion loss of agricultural land resource depletion reduced biodiversity disease pest resistance fossil fuel consumption pollution population migration conflict 2

3 1930s 250,000 people 1990s >1 million people Machakos in sub-saharan Africa More people = less erosion? Population quadrupled Labor force increased WWII brought new technology Land was terraced, irrigated, fertilized Nearby Nairobi grew and provided market for farm products Soil conditions improved Food stability, increased income led to better education and lower birth rates What made Machakos different than expected? Consequences of exploding populations Perspective 1 (economic gloom): Overuse and degradation of resources, environmental degradation, famine, suffering and conflict Perspective 2 (economic boom): Increased labor, increased ideas and innovation, increased economic growth, solutions to environmental problems, increased carrying capacity Populations and age structure Age-structure in China 1982 After reaching replacement fertility, China continued growth due to population momentum Often requires 2 generations (~ 50 y) to slow population growth. Nigeria Country Japan 158 Population (millions) Fertility rate Life expectancy Infant death rate ,000 Infant deaths per year statistics, UNPD 2000 Baby boom echo 3

4 China s missing girls Demographic dividend Resources and human fertility Fertility Rate Total fertility rate and income (2007) Per capita income ($) Data from WHO, World Health Statistics 2009 Resources and human fertility rates Plot from Baerlocher (2007) Canadian Medical Association Journal 4

5 Global patterns in fertility Projected population growth Literacy, income and fertility Geographical patterns of female illiteracy Fertility Rate Total fertility rate and literacy (2007) R2= Adult literacy (%) Data from WHO, World Health Statistics

6 What do the literacy data suggest? Education and fertility in the US Children born per 1000 women 2,500 2,000 1,500 1, Not a high school graduate High school, 4 years US Census Bureau data 2006 Some college, no degree Associate degree Bachelors degree Graduate or professional degree Availability of contraceptives Fertility Rate R² = Contraceptive use (%) Data from WHO, World Health Statistics 2009 Incentives for high fertility High infant mortality rates Economic benefits of children Improves future security Women s status Motherhood in developing countries starts ~ 17 y Average marriage age in developed world: 25-27y 6

7 Declining death rates and population growth rates Causes of disease recognized Improvements in nutrition Discovery of antibiotics Improvements in medicine Increase in # of women who reach child-bearing age Short generation times in some countries Demographic transition Epidemiologic transition Fertility transition Summary: Continued high birth rates and short generation times with declining mortality rates lead to rapid population growth Primitive stability Epidemiologic transition Fertility transition Modern stability Time Demographic transition in India Regions in transition Figure from Wright (2005) 7

8 Sustainable development Developed countries helping developing nations to improve living conditions without sacrificing resources of future generations Principles: 1: Education (literacy) 2: Health: nutrition, hygiene 3: Family planning 4: Enhance income 5: Resource management: sustainable use One expected result: Reduced population growth rates by moving nations through the demographic transition Sustainable development and the World Bank Loans money to developing countries to start moneymaking programs Idea: Lend money start a development project. Project makes money repay the loan. Problems: If project fails, country s debt increases. If corrupt officials steal the money, debt increases. If programs are not sustainable (e.g., cutting down rain forest for ranching), debt increases and natural resources diminish. One solution: micro loans Complications to sustainable development Poverty War Corruption Hunger HIV Big Challenges Population growth rates and HIV/AIDS (2006) HIV infection rate in Swaziland: 26% (2011) Life expectancy: < 50 y 8

9 What can you do to affect population growth rates? Projecting the future Support sustainable development programs Support women s rights and family services worldwide Problems to consider: Dark side of large-scale sustainable development Coercion as family planning Differences in values Problems are complex and unfamiliar Asimov Malthus Ehrlich 9