Chapter 7 Human Population Change and the Environment

Population Growth In China Largest population in the world Largest population in the world 1971: government involved 1971: government involved More aggressive plan More aggressive plan One-child policy One-child policy Why do it? Why do it?

Population Growth In China 1984: program relaxed; why? 1984: program relaxed; why? 1970: 5.8 children/woman 1970: 5.8 children/woman 2006: 1.7 children/woman 2006: 1.7 children/woman Ethical issues Ethical issues

India’s Population Pressures World’s second most populous nation World’s second most populous nation 1.2 billion 1.2 billion 1950s - government sponsored family planning 1950s - government sponsored family planning Number of children per woman declined from 5.3 (1980) to 2.7 (2009) Number of children per woman declined from 5.3 (1980) to 2.7 (2009) Despite success Despite success Population pressure has cause environmental degradation Population pressure has cause environmental degradation 76% live under poverty level (less than $2 /day) 76% live under poverty level (less than $2 /day)

India’s Population Pressures

Population Ecology Branch of biology Branch of biology Study of populations Study of populations Individuals of a given species Individuals of a given species How they respond to the environment How they respond to the environment Look for similarities Look for similarities

How Populations Change Global scale: dependent on two things Global scale: dependent on two things Birth rate (b) Birth rate (b) Death rate (d) Death rate (d) Growth rate (r) Growth rate (r) r = b - d r = b - d

How Populations Change Local populations Local populations Dispersal Dispersal Immigration (i) Immigration (i) Emigration (e) Emigration (e)

Population Ecology Maximum Population Growth Maximum Population Growth Biotic Potential (maximum rate of increase under optimal conditions) Biotic Potential (maximum rate of increase under optimal conditions) Life history characteristics: Life history characteristics: Age at first reproduction Age at first reproduction Reproductive fraction of life span Reproductive fraction of life span Number of reproductive periods/events Number of reproductive periods/events Number of offspring per reproductive event Number of offspring per reproductive event

Average Number of Children, Grandchildren, and Great Grandchildren America America West Germany West Germany Africa Africa

Maximum Population Growth Biotic potential Biotic potential Maximum rate at which population can increase Maximum rate at which population can increase Determined by life history characteristics Determined by life history characteristics Large organisms ---> smallest biotic potentials Large organisms ---> smallest biotic potentials Microorganisms ---> largest biotic potentials Microorganisms ---> largest biotic potentials

Exponential Population Growth Optimal conditions Optimal conditions Constant reproductive rate Constant reproductive rate J-shaped curve J-shaped curve

Environmental Resistance Unfavorable environmental conditions Unfavorable environmental conditions Prevent reproduction at biotic potential Prevent reproduction at biotic potential Examples? Examples? Environment controls population size: how? Environment controls population size: how?

Carrying Capacity Largest population that can be sustained indefinitely Largest population that can be sustained indefinitely Changes in response to environment Changes in response to environment J-shaped curve ---> S-shaped curve J-shaped curve ---> S-shaped curve

Carrying Capacity Populations are always changing Populations are always changing Slightly above or below carrying capacity Slightly above or below carrying capacity Too high ---> crash Too high ---> crash

Population Ecology Environmental Resistance: Environmental Resistance: Environmental factors that limit the exponential growth of populations Environmental factors that limit the exponential growth of populations Food, water, shelter, disease, predation, waste accumulation Food, water, shelter, disease, predation, waste accumulation As the environment deteriorates As the environment deteriorates population growth declines population growth declines death rate increases death rate increases The environment controls population size The environment controls population size As the population grows, so does environmental resistance, which limits population growth As the population grows, so does environmental resistance, which limits population growth Exponential growth is no longer possible Exponential growth is no longer possible

The Human Population 7 billion by billion by 2012 Why the increase? Why the increase?

Thomas Malthus British economist British economist Hypothesized that human population would be kept in check: how? Hypothesized that human population would be kept in check: how? Thinking shaped by rapid urbanization & industrialization Thinking shaped by rapid urbanization & industrialization Was he correct? Was he correct?

Projecting Future Population World growth rate has declined slightly World growth rate has declined slightly Zero population growth Zero population growth Birth rate = death rate Birth rate = death rate End of 21 st century End of 21 st century U.N. predicts billion by 2050 U.N. predicts billion by 2050

Calculating Fertility Rates and Doubling Times (CBR – CDR)/10 = Rate of increase or decrease in population per 1,000 per year 70/Rate of Increase = Doubling Time

Calculating Fertility Rates and Doubling Times: Practice

Demographic Transition Comparisons

Earth’s Carrying Capacity 4 billion – 16 billion people 4 billion – 16 billion people Why such a large range? Why such a large range? What could happen to the environment? What could happen to the environment? Have we already exceeded our carrying capacity? Have we already exceeded our carrying capacity?

Demographics of Countries Demographics: Demographics: Applied branch of sociology that deals with population statistics Applied branch of sociology that deals with population statistics Countries are grouped by Countries are grouped by Population growth rates Population growth rates Degree of industrialization Degree of industrialization Relative prosperity Relative prosperity GNI PPP = gross national income in purchasing power parity GNI PPP = gross national income in purchasing power parity Per person GNI PPP = GNI PPP/number of people Per person GNI PPP = GNI PPP/number of people The amount of goods and services an average citizen of a particular country could buy in the US The amount of goods and services an average citizen of a particular country could buy in the US

Demographics Study of populations Study of populations Highly developed countries Highly developed countries Low birth rates Low birth rates Low infant mortality Low infant mortality Longer life expectancies Longer life expectancies High GNI PPP High GNI PPP

Demographics Less developed countries Less developed countries High birth rates High birth rates High infant mortality High infant mortality Shortest life expectancies Shortest life expectancies Low GNI PPP Low GNI PPP

Demographics of Countries

Highly Developed Countries Highly Developed Countries Lowest birth rates (some have shrinking pops) Lowest birth rates (some have shrinking pops) Low infant mortality rates Low infant mortality rates Longer life expectancies Longer life expectancies Highest per capita GNI PPP Highest per capita GNI PPP Moderately Developed Countries Moderately Developed Countries Higher birth and infant mortality rates Higher birth and infant mortality rates Medium industrialization Medium industrialization Lower GNI PPP Lower GNI PPP Less Developed Countries Less Developed Countries Shortest life expectancies Shortest life expectancies Highest birth and infant mortality rates Highest birth and infant mortality rates

Total Fertility Rate TFR: average number of children born to each woman TFR: average number of children born to each woman Replacement rate = 2.1 Replacement rate = 2.1 Current TFR = 2.6 Current TFR = 2.6

Demographic Transition Country moves from high birth and death rates to low birth and death rates Country moves from high birth and death rates to low birth and death rates Four stages Four stages Preindustrial Preindustrial Transitional Transitional Industrial Industrial Postindustrial Postindustrial

Demographic Transition

The Demographic Transition

What happens when a population reaches the 4 th stage? What happens when a population reaches the 4 th stage? We don’t know: We don’t know: We see that TFR are dropping as countries become more industrialized We see that TFR are dropping as countries become more industrialized Brazil Brazil 1960 = 6.7 children/woman, 2010 = = 6.7 children/woman, 2010 = 2 Worldwide Worldwide 1970 = 6.1 children/woman, 2010 = = 6.1 children/woman, 2010 = 2.7 Despite great advances, population still increasing Despite great advances, population still increasing

Demographic Transition Population is stabilizing in some countries Population is stabilizing in some countries Can all developing countries get there? Can all developing countries get there?

Age Structure Number and proportion of people in each age group in a population Number and proportion of people in each age group in a population Helps predict future growth Helps predict future growth Shape is important Shape is important Pyramid = fast growth Pyramid = fast growth Tapered bases = slow or negative growth Tapered bases = slow or negative growth

Age Structure Diagrams

Future Population Growth Determined by prereproductive individuals Determined by prereproductive individuals Developed vs. developing countries Developed vs. developing countries

Stabilizing World Population Dispersal is not a solution Dispersal is not a solution Increase the death rate? Increase the death rate? Reduce the birth rate! Reduce the birth rate!

Culture and Fertility Gender and society Gender and society Different societies have different expectations; impacts fertility rates Different societies have different expectations; impacts fertility rates

Culture and Fertility High TFRs may be traditional High TFRs may be traditional High infant mortality rates High infant mortality rates Children can work Children can work Males more valued Males more valued Religious values Religious values Changing traditions takes time Changing traditions takes time

Status of Women Gender inequality still exists Gender inequality still exists Most developing countries Most developing countries More illiterate women More illiterate women Fewer women attend secondary school Fewer women attend secondary school Limits women Limits women

Status of Women Low status of women is single most important factor influencing TFR Low status of women is single most important factor influencing TFR Average age at marriage impacts TFR Average age at marriage impacts TFR Sri Lanka: 25; TFR = 2.0 Sri Lanka: 25; TFR = 2.0 Bangladesh: 17; TFR = 3.0 Bangladesh: 17; TFR = 3.0 More education = less children; why? More education = less children; why?

Family Planning Services Prenatal care, proper birth spacing Prenatal care, proper birth spacing Healthier women ---> healthier babies ---> fewer infant deaths ---> lower TFR Healthier women ---> healthier babies ---> fewer infant deaths ---> lower TFR Provide information and contraceptives Provide information and contraceptives Local social and cultural beliefs Local social and cultural beliefs

Government Policies & Fertility Laws determining minimum marriage age Laws determining minimum marriage age Budget for family planning, education, health care, old-age security Budget for family planning, education, health care, old-age security Economic rewards and penalties Economic rewards and penalties Many countries recognize the problem Many countries recognize the problem

Population and Urbanization Human population becoming more urbanized Human population becoming more urbanized 79% U.S. population lives in cities; why? 79% U.S. population lives in cities; why?

Population and Urbanization Cities more heterogeneous Cities more heterogeneous More young people in cities More young people in cities Developing countries: more males in cities; why? Developing countries: more males in cities; why? Developed countries: more females in cities; why? Developed countries: more females in cities; why?

Environmental Problems of Urban Areas Encroachment into habitat Encroachment into habitat Brownfields Brownfields Long commute ---> more air pollution Long commute ---> more air pollution Buildup of emissions Buildup of emissions Paved roads, buildings affect water flow Paved roads, buildings affect water flow

Environmental Benefits of Urbanization Compact development Compact development Tall, multiple-unit residential buildings are close to shops and jobs Tall, multiple-unit residential buildings are close to shops and jobs Connected by public transportation Connected by public transportation Reduces pollution Reduces pollution Preserves rural areas Preserves rural areas Requires smart planning! Requires smart planning!

Urbanization Trends Currently ≈ 47% world’s population lives in urban areas Currently ≈ 47% world’s population lives in urban areas Most large cities are in developing countries Most large cities are in developing countries If urban growth is too fast, basic services cannot keep up If urban growth is too fast, basic services cannot keep up

Urbanization Trends

Population and Urbanization Urbanization Trends Urbanization Trends Highly Developed Countries ( e.g., US) Highly Developed Countries ( e.g., US) Most migration to cities in last 150 yrs Most migration to cities in last 150 yrs Need for industrial labor Need for industrial labor Slow growth, services could keep up Slow growth, services could keep up Water purification, sewage treatment, education, adequate housing Water purification, sewage treatment, education, adequate housing Developing Countries Developing Countries Rapid growth - cities can’t provide basic services Rapid growth - cities can’t provide basic services Low job possibilities (still greater than in rural areas) Low job possibilities (still greater than in rural areas) Substandard housing (slums) Substandard housing (slums) Poverty Poverty Unemployment Unemployment Pollution, water, and sewage issues Pollution, water, and sewage issues

Case Study Urban Planning in Curitiba, Brazil Urban Planning in Curitiba, Brazil 2.9 million people 2.9 million people Efficient mass transit system Efficient mass transit system High density development restricted to buss lines (72% of commuters use the bus) High density development restricted to buss lines (72% of commuters use the bus) Since 1970s, population has doubled, but traffic has declined 30% Since 1970s, population has doubled, but traffic has declined 30% Less traffic congestion Less traffic congestion Cleaner air Cleaner air “Big Sidewalk” of 49 blocks of pedestrian walkways connected to bus stops, parks, and bicycle paths “Big Sidewalk” of 49 blocks of pedestrian walkways connected to bus stops, parks, and bicycle paths Excellent example of compact urban planning Excellent example of compact urban planning