5.2 ENVR201_Human Population Dynamics Part2.pptx

Population structure

1. ENVR 201 Introduction to Environmental Sciences Human Population Lesson 2

2. Objectives After this class you will be able to: Understand Age structure Understand population dynamics Identify Human Population’s Effects on the Earth Understand the concept of ”Carrying Capacity” of Earth 2

3. Projecting Future Population Growth Doubling Time the number of years it takes for a population to double, assuming a constant rate of natural increase. The standard way to estimate doubling time is to assume that the population is growing exponentially and then divide 70 by the annual growth rate stated as a percentage. (Dividing into 70 is a consequence of the mathematics of exponential growth.). 3

4. Doubling time 4 Year Growth Rate Doubling Time 1970 2.09 34 years 1980 1.82 38 years 1990 1.60 44 years 2000 1.26 56 years 2010 1.12 63 years 2017 1.11 63 years Could you calculate in how many years Pakistani population would be doubled?

5. Population Growth Curve Population growth follows a smooth S-shaped curve known as the Logistic Growth Curve. 5 A logistic population would increase exponentially only temporarily . After that, the rate of growth would gradually decline (i.e., the population would increase more slowly) until an upper population limit, called the logistic carrying capacity , was reached. Once that had been reached, the population would remain at that number.

6. Age Structure Age structure—express how population is divided among age groups The age structure of a population affects current and future birth rates, death rates, and growth rates; has an impact on the environment; and has implications for current and future social and economic conditions. 6

7. Population Dynamics and Control Age Structure We can picture a population’s age structure as a pile of blocks, one for each age group, with the size of each block representing the number of people in that group. Although age structures can take many shapes, four general types are most important: a pyramid, a column, and a column with a bulge. an inverted pyramid (top-heavy)

8. This type indicates growing population. Examples India, Bangladesh, Ethiopia, Nigeria, Pakistan. The large number of individuals in very young age will soon enter into reproductive age, thus causing an increase in population, whereas less number of people in old age indicate less loss of population due to death. 8 Few older people Many young people Expanding population

9. Stable population Baby boom France, USA and Canada where birth rates have in the past one or two decades declined resulting in people of almost equal number in age group 0-35 years. So in the next 10 years, the people entering into reproductive age group is not going to change much and such age-pyramids indicate stable populations

10. Declining population Here number of individuals in very young class is smaller than the middle reproductive age class. In the next 10 years the number in reproductive age class will thus become less than before resulting in a decline of population growth. Germany, Italy, Hungary, Sweden and Japan are examples of this type

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12. Demographic Transition 13 Developed countries Developing countries

13. How to lower the human birth rate and decrease our population growth? Age of First Childbearing Birth Control: Biological and Societal National Programs to Reduce Birth Rates Promote Economic Development Promote Family Planning Empowering Women Can we achieve zero population growth? 14

14. UN Projections of Human Growth Based on potential total fertility rates (TFR) Copyright © 2014 by John Wiley & Sons, Inc. 15 https:// www.worldometers.info /world-population/

15. Human impacts on Environment The planet and its resources are finite, and it cannot support an infinite population of humans or any other species. 16 https:// www.worldometers.info /world-population/

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

17. Causes of Mortality

18. Population: the Multiplier of Everything Else TERM! Carrying Capacity

19. Population: the Multiplier of Everything Else TERM! Carrying Capacity The population (number of individuals) a given space can sustain.

20. Carrying Capacity Global human population was <1 billion in 1800. Population has doubled just since 1963. We add 2.5 people every second (79 million/year) What does this mean for Carrying Capacity?

21. Carrying Capacity Technology has allowed us to raise Earth’s carrying capacity for our species Tool-making, agriculture, and industrialization each enabled humans to sustain greater populations.

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

23. Human Carrying Capacity Limiting factors Short-term —affect population immediately Example: food shortages Intermediate-term —affect population for 1-10 years Example: desertification, dispersal of pollutants Long-term —effects not apparent until after 10 years Example: soil erosion, decline in groundwater supply, climate change

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

25. Env. Impacts of Population Hunger/Famine Political unrest Environmental degradation erosion, desertification, strip mining, oil spills, groundwater mining Water pollution Air pollution Extinctions 26

26. Measuring Env. Impacts of Population I=PAT I mpacts are a result of P opulation, A ffluence, and T echnology. This is a simplification of reality to explain the impacts of human population. MODEL! I= Impact on the environment P= Population size A= Affluence (amount of resources consumed per person) T= Technology (effects of methods used to provide items consumed).