1. Chapter 4: The Human Population and the Environment

2. Overview Basic Concepts of Population Dynamics Basic Concepts of Population Dynamics Projecting Future Population Growth Projecting Future Population Growth Age Structure Age Structure The Demographic Transition The Demographic Transition Longevity and its Effects on Population Growth Longevity and its Effects on Population Growth The Human Population’s Effects on the Earth The Human Population’s Effects on the Earth The Human Carrying Capacity of the Earth The Human Carrying Capacity of the Earth Can We Achieve Zero-population Growth? Can We Achieve Zero-population Growth?

3. Basic Concepts of Population Dynamics Population Dynamics Population Dynamics A general study of population changes A general study of population changes Population Population Group of individuals of the same species living in the same area Group of individuals of the same species living in the same area Species Species All individuals that are capable of interbreeding All individuals that are capable of interbreeding A species is made up of populations A species is made up of populations Demography Demography statistical study of human populations statistical study of human populations

4. Basic Concepts of Population Dynamics Five key properties of any population Five key properties of any population Abundance Abundance Birth rates Birth rates Death rates Death rates Growth rates Growth rates Age structure Age structure Human Population data often reported as crude rates (per 1000 people) Human Population data often reported as crude rates (per 1000 people)

5. Kinds of Population Growth Exponential Growth Exponential Growth A pop increasing by a constant percentage per unit time. A pop increasing by a constant percentage per unit time. Human pop growth peaked at 2.1% Human pop growth peaked at 2.1% 1965-1970 1965-1970 Now at 1.2% Now at 1.2%

6. US Population Growth

7. History of Human Population Growth 1. Early period of hunter and gathers Total population < a few million Total population < a few million 2. Rise of agriculture Allowed for increase in population density and increase in human population Allowed for increase in population density and increase in human population 3. Industrial revolution Improvements in health and food supply led to rapid increase in population Improvements in health and food supply led to rapid increase in population 4. Today Rate of growth slow in industrialized nations but high in less developed nations Rate of growth slow in industrialized nations but high in less developed nations

8. Human Population Growth

9. Projecting Future Population Growth Doubling time Doubling time Time required for a pop to double in size Time required for a pop to double in size Calculated by dividing annual growth rate (%) into 70 Calculated by dividing annual growth rate (%) into 70 It changes quickly as growth rate changes It changes quickly as growth rate changes Examples Examples US w/ a growth rate of 0.6%, doubling time = 117 yrs US w/ a growth rate of 0.6%, doubling time = 117 yrs Nicaragua w/ a growth rate of 2.7%, doubling time = 26 yrs Nicaragua w/ a growth rate of 2.7%, doubling time = 26 yrs Northern Europe w/ a growth rate of 0.2%, doubling time = 350 yrs Northern Europe w/ a growth rate of 0.2%, doubling time = 350 yrs

10. Doubling Time

11. World Growth Rate Peaked in 1960s at 2.2% Peaked in 1960s at 2.2% Currently at 1.1% Currently at 1.1% Current doubling time = 66 years Current doubling time = 66 years

12. Logistic Growth Curve Growth cannot continue forever (exponential growth) Growth cannot continue forever (exponential growth) Logistic Growth Logistic Growth S shaped curve S shaped curve Growth increase exponentially only temporarily, until hits inflection point Growth increase exponentially only temporarily, until hits inflection point Reach an upper pop limit at the logistic carrying capacity where the growth rate = 0 Reach an upper pop limit at the logistic carrying capacity where the growth rate = 0

13. Logistic Growth Curve Little evidence that animal populations actually follow this growth curve Little evidence that animal populations actually follow this growth curve Involves assumptions Involves assumptions Constant environment Constant environment Constant carrying capacity Constant carrying capacity Homogeneous population Homogeneous population Unlikely if death rate continue to decrease Unlikely if death rate continue to decrease

14. UN Projections of Human Growth Based on potential total fertility rates (TFR)

15. Age Structure Exponential and Logistic Growth curves ignore characteristics of the environment that affect different age groups Exponential and Logistic Growth curves ignore characteristics of the environment that affect different age groups Food, water, shelter, disease Food, water, shelter, disease Age Structure- express how population is divided among age groups Age Structure- express how population is divided among age groups Implication for current and future social and economic conditions Implication for current and future social and economic conditions Impact on the environment Impact on the environment

16. Age Structure- 4 Types Pyramid - population w/ many young and high death rate (short average lifetime) Pyramid - population w/ many young and high death rate (short average lifetime) Inverted pyramid - population with large elderly population and small youth population (declining growth) Inverted pyramid - population with large elderly population and small youth population (declining growth)

17. Age Structure- 4 Types Column - birth rate and death rate are low, little change in population size Column - birth rate and death rate are low, little change in population size Column w/ a bulge - event in the past caused a high birth or death rate for some age group Column w/ a bulge - event in the past caused a high birth or death rate for some age group

18. Demographic Transition Three stage pattern of change in birth rates and death rates Three stage pattern of change in birth rates and death rates Occurred during the process of industrial and economic development of Western nations Occurred during the process of industrial and economic development of Western nations Leads to decline in population growth rate Leads to decline in population growth rate

19. Demographic Transition Stage 1 Stage 1 Decline in death rate Decline in death rate Developed countries (top) and Developing countries (bottom) Developed countries (top) and Developing countries (bottom) Stage 2 Stage 2 Period of high growth rate Period of high growth rate W/ industrialization death rate declines but birth rate stays high W/ industrialization death rate declines but birth rate stays high

20. Demographic Transition Stage 3 Stage 3 Birth rate drops toward death rate Birth rate drops toward death rate Growth rate decreases Growth rate decreases Will take place if parents come to believe that having a small family is to their benefit Will take place if parents come to believe that having a small family is to their benefit

21. Potential Effects of Medical Advances on Demographic Transition Second decline in death rate Second decline in death rate Leads to Stage IV Leads to Stage IV A second stable state would arise if birth rate then falls A second stable state would arise if birth rate then falls Stage V Stage V Decision needs to be made Decision needs to be made Stop research on diseases of old age Stop research on diseases of old age Reduce birth rate Reduce birth rate Or do neither and wait for Malthus’ projections Or do neither and wait for Malthus’ projections

23. Changes in birth and death rates from 1775- 2000 in developed and developing countries

24. Longevity and its Effects on Population Growth Maximum lifetime Maximum lifetime Maximum possible age to which an individual in a species can live Maximum possible age to which an individual in a species can live Life expectancy Life expectancy Average number of years an individual in a species can expect to live Average number of years an individual in a species can expect to live Higher in developed, prosperous nations Higher in developed, prosperous nations Japan highest at 82.1 years Japan highest at 82.1 years Swaziland lowest at 32 years Swaziland lowest at 32 years

25. Longevity and Population Growth Population growth occurred in human history with little change in maximum lifetime Population growth occurred in human history with little change in maximum lifetime Changes were in birth rates, death rates, age structure, etc. Changes were in birth rates, death rates, age structure, etc.

26. Effect of Rise of Industrial Societies Modern medicine has reduced death rates Modern medicine has reduced death rates Acute diseases Acute diseases Appears rapidly in the population and then disappears Appears rapidly in the population and then disappears Currently 60% of mortality in Ecuador, 20% in US Currently 60% of mortality in Ecuador, 20% in US Chronic diseases Chronic diseases Always present in population (cancer, heart disease, etc.) Always present in population (cancer, heart disease, etc.) Currently 70% of mortality in US, 20% in Ecuador Currently 70% of mortality in US, 20% in Ecuador These figures have changed over time (see next slide) These figures have changed over time (see next slide)

28. Human Population Effects on Earth Impact that all humans pose on the environment is a result of two factors Impact that all humans pose on the environment is a result of two factors Number of people Number of people Impact of each person on the environment Impact of each person on the environment T = P x I T = P x I T = Total impact of the human population on environment T = Total impact of the human population on environment P = average impact of an individual P = average impact of an individual T = total # of individuals T = total # of individuals

29. Human Population Effects on Earth Modern technology increases the use of resources and enables us to effect the environment in new ways Modern technology increases the use of resources and enables us to effect the environment in new ways Examples: CFCs, automobiles Examples: CFCs, automobiles (T = P x I) equation reveals irony: (T = P x I) equation reveals irony: Improving standard of living increases P Improving standard of living increases P Countering the benefits of declining I Countering the benefits of declining I

30. Human Carrying Capacity How many people can live on Earth at the same time? How many people can live on Earth at the same time? Depends on the quality of life people desire and are willing to accept Depends on the quality of life people desire and are willing to accept Estimation methods Estimation methods Extrapolation from past growth Extrapolation from past growth Packing problem approach Packing problem approach Deep Ecology Deep Ecology

31. Human Carrying Capacity Limiting Factors Limiting Factors Short Term- effect population immediately Short Term- effect population immediately Ex: Food shortages Ex: Food shortages Intermediate Term- effect population for 1-10 years Intermediate Term- effect population for 1-10 years Ex: desertification, dispersal of pollutants, etc. Ex: desertification, dispersal of pollutants, etc. Long Term- effects not apparent until after 10 years Long Term- effects not apparent until after 10 years Ex: soil erosion, decline in groundwater supply, climate change Ex: soil erosion, decline in groundwater supply, climate change

32. Can We Achieve Zero Population Growth? Possible approaches Possible approaches Delay age of first child bearing Delay age of first child bearing Birth control Birth control National programs to reduce birth rates National programs to reduce birth rates Information (education) Information (education) Increase access to birth control Increase access to birth control