1. Population & Environment I ES 118 Spring 2008

2. Weeks 1 23 45 Population (millions) 1.3 2.6 3.9 5.2 Size of US every 3.7 years Size of Germany every year

4. 20 th Century: The Population Century 20 th Century: The Population Century –1900: 1.6 billion –2000: 6.1 billion, avg. population density 45 people/km 2

5. Population and environment What are different perspectives on the importance of population and the environment? What are different perspectives on the importance of population and the environment? How are populations measured and described? How are populations measured and described? What factors and policies influence population growth and environmental impact? What factors and policies influence population growth and environmental impact? What does the future hold? What does the future hold?

6. Modern debates Few debates in the social and environmental sciences as heated or protracted as the debate over the consequences of population growth Few debates in the social and environmental sciences as heated or protracted as the debate over the consequences of population growth Several broad positions (“paradigms”) Several broad positions (“paradigms”)

7. Historical dimensions Thomas Malthus 1798: An Essay on the Principle of Population Thomas Malthus 1798: An Essay on the Principle of Population –Population tends to increase exponentially, food production tends to increase slowly, so populations will outstrip food supply –Need “positive checks” (e.g., disease or famine) or “preventative checks” (e.g., “moral restraint”) –Argued that poverty is an eventual consequence of population growth

8. Neo-Malthusians Argue that we are approaching or have surpassed earth’s physical capacity to sustain growth Argue that we are approaching or have surpassed earth’s physical capacity to sustain growth Paul Ehrlich (The Population Bomb): “The battle to feed humanity is over…” Paul Ehrlich (The Population Bomb): “The battle to feed humanity is over…” Paul R. Ehrlich, Stanford

9. Population growth no problem Some neoclassical economists have argued population growth not a problem, and may be a source of progress Some neoclassical economists have argued population growth not a problem, and may be a source of progress –Ester Boserup –Julian Simon Population growth stimulates investment in increased efficiency, resource substitution, conservation, and innovation Population growth stimulates investment in increased efficiency, resource substitution, conservation, and innovation

10. Inequality arguments Population growth and environmental problems caused by social structural arrangements that produce inequality Population growth and environmental problems caused by social structural arrangements that produce inequality Karl Marx: Population a symptom, rather than a root cause, of poverty, resource depletion, pollution, etc. Karl Marx: Population a symptom, rather than a root cause, of poverty, resource depletion, pollution, etc. Neo-Marxians Neo-Marxians –Eliminating oppression and poverty through technological development and social justice will solve the problem –Francis Moore Lappé

11. Population-environment links What is the relationship between environmental impact and population? What is the relationship between environmental impact and population? I = P x A x T (“ipat”) (Ehrlich and Holdren) I = P x A x T (“ipat”) (Ehrlich and Holdren) –I = Environmental impact –P = Population –A = Affluence (consumption) –T = Technological impact per unit of consumption(+ or -)

12. Demographic concepts Natality: Number of individuals added to population Natality: Number of individuals added to population –Birth rate: number of individuals born each year Mortality: Number of deaths in a population Mortality: Number of deaths in a population –Death Rate: number of individuals that die each year Population Growth Rate Population Growth Rate –Birthrate – Death rate = (Births + Immigration) – (Deaths + Emigration) Population Change

13. Demographic measures Crude birth rate: Live births per 1,000 people a year Crude death rate: Deaths per 1,000 people a year Growth rate Birth Rate – Death Rate 1,000 persons X 100 = Example: If worldwide birth rate 21/1,000 and death rate 9/1,000, growth rate 12/1,000 or 1.2%

14. Example Q: What is the annual population increase in the United States (excluding migration) assuming the following birth rate and death rate? BR in US: 14/1,000 DR in US: 8/1,000 Growth rate 14 – 8_____ 14 – 8_____ 1,000 persons X 100 = _____6_____ 1,000 persons = 0.006 X 100 =

15. Doubling time Doubling Time (years) = 70 / Growth Rate (%) Current global GR = 1.2%; DT=58 years

16. Carrying capacity Populations with few or no resource limitations tends to grow exponentially Populations with few or no resource limitations tends to grow exponentially The ultimate size of a population is constrained by the carrying capacity of the environment The ultimate size of a population is constrained by the carrying capacity of the environment Maximum sustainable population for an area Maximum sustainable population for an area –Determined by limiting factors –Not fixed—can change (e.g., more food) 500,00010,0008,0006,0004,0002,0000 1 6 5 4 3 2 7 1 6 5 4 3 2 7 Years Before Present Billions of People

17. Time Population size Population growth - models Carrying capacity K

18. Factors that limit growth Extrinsic Extrinsic –Regulated by factors from outside –Ex: Loss of food, predators, accidents Intrinsic Intrinsic –Regulated by factors inside population –Ex: Behavioral changes with overcrowding Density-dependent Density-dependent –Become more effectives as populations density increases –Ex: Larger population, predation or disease more likely Density-independent Density-independent –Ex: Natural catastrophes independent of population density

19. Types of limiting factors Raw materials Raw materials –Nutrients, water Energy Energy –Plants require sunlight; animals food for energy Waste Waste –Bacteria colonies collapse if too much waste Interactions with other organisms Interactions with other organisms

20. Total Fertility Rate (TFR) A major indicator of population growth A major indicator of population growth Provides estimate of how many children women would have in their lifetime if the birth rates remained unchanged Provides estimate of how many children women would have in their lifetime if the birth rates remained unchanged Replacement-level fertility: Number of children a couple must bear to replace themselves Replacement-level fertility: Number of children a couple must bear to replace themselves –~2.1 in developed countries ~2.5 in developing countries

21. Demographic divide On one side, mostly poor countries with relatively high birth rates On one side, mostly poor countries with relatively high birth rates On the other, mostly wealthy countries with birth rates so low populations declining On the other, mostly wealthy countries with birth rates so low populations declining

22. Global TFR trends 1950-2005 average number of children per women fell from 5.0 to 2.7 1950-2005 average number of children per women fell from 5.0 to 2.7 –In developed countries fell from 2.5 to 1.6 –In less developed countries, fell from 6.2 to 3.0 –Sub-Saharan Africa remains above 5.0

23. Local TFR variation

24. Fertility and population growth These countries have similar population sizes today, but will diverge dramatically because of their different levels of fertility.

25. Countries with high TFR Widespread poverty Widespread poverty Largely rural populations Largely rural populations High rates of illiteracy High rates of illiteracy Minimal use of family planning Minimal use of family planning No “safety net” outside of the family No “safety net” outside of the family High rates of child mortality High rates of child mortality –Nigeria: 100 infants die out of 1,000 births (vs 59/1,000 for all less developed countries and 6/1,000 for more developed countries)

26. Countries with low TFR Some countries have low or declining TFR (Italy and South Korea 1.2, Japan 1.3, Northern 1.7 and Western Europe 1.6 children per woman Some countries have low or declining TFR (Italy and South Korea 1.2, Japan 1.3, Northern 1.7 and Western Europe 1.6 children per woman –Rising expectations for material goods and living standards –Uncertainty and tight housing and labor markets –Targeted policies and programs –Women waiting longer for marriage and children –Cohabitation less accepted and common

27. Age Structure (Distribution) Number of individuals in each stage in the population Number of individuals in each stage in the population –Influenced by growth rate –If most of the population is young (reproductive or pre-reproductive), population will grow –If most of population is older (post- reproductive), population may fall

28. Population age structure (distribution) Prereproductive Reproductive Postreproductive

29. Population age structure

30. Global patterns in growth Most countries projected to grow Most countries projected to grow Negative growth countries Negative growth countries –< 15% projected to lose population, accounting for less than 1 billion people (<10% of world’s population 2050) Slow growth countries Slow growth countries –25% will grow slowly –China: Fertility has fallen so low, deaths will outnumber births in 2030, but will still add 110 million to reach 1.4 billion in 2050

31. 2005-2050 Patterns of growth Moderate growth countries Moderate growth countries –U.S. projected to increase 42% between 2005- 2050, adding > 100 million people (but note: “slow growth” if just birth rate considered without immigration) –Other examples: Bangladesh, Brazil, India, Indonesia, and Iran –These countries account for just 8% of world population today, but likely will account for 20% by 2050

32. Demographic transition

33. Demographic transition in Sweden and Mexico

34. Global comparisons How have fertility rates and death rates changed by country and region over time? How have fertility rates and death rates changed by country and region over time?