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The Issues

The Issues. #1: Populations. Here are some key words. Carrying Capacity Geometric Growth Growth versus Limits “Overpopulation” Birth Rate Death Rate Demographic Transition. What is a “Population?”. It is ‘all of the members of a species living in a given area at the same time”

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The Issues

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  1. The Issues #1: Populations.

  2. Here are some key words • Carrying Capacity • Geometric Growth • Growth versus Limits • “Overpopulation” • Birth Rate • Death Rate • Demographic Transition

  3. What is a “Population?” • It is ‘all of the members of a species living in a given area at the same time” • The word “population” does not specifically refer to the human population. • We look at populations in terms of size, composition and trends.

  4. What is the size of Earth’s Population? • It is over 6 billion • We reached the first billion when? • 1800 • Now we add a billion in 40 years

  5. Initially there are just two pads living happily with the whole lake to themselves. Suppose the lake is so nurturing that the total number of lily pads doubles each year, and that it takes 1 billion lily pads to completely cover the lake. The number of lily pads on the lake after 10 years is 210 = 1,024; hardly noticeable, covering only about one millionth of the lake's surface. After 20 years the number is 220 = 1,048,576 which still covers only 1 thousandth of the lake's surface. After a quarter century the lake is still only 3% covered by lily pads. At year 28, however, the lake is one quarter covered and crowding and lack of nutrients may be a serious problem. In only two more years the lake is completely covered. The type of curve is called “exponential” • Such a curve is ultimately unsustainable, but is common in nature

  6. Geometric Growth • Is growth at a constant rate of increase per unit of time, so each time you add a constant percentage to an ever-growing population • Arithmetic growth is when the population grows by a constant amount each unit of time.

  7. “Boom and Bust” • We see this pattern of explosive growth and collapse in nature, and call it the “boom and bust” phenomenon.

  8. The Big Question • Are we headed along the “Boom and Bust” road? • This is a question that has bothered people since human population began to grow at the end of the c18 • In particular, it worried one man, a minister of the church and an economist

  9. But, it did not happen, and now we are 6 billion. Was he wrong? The Problem • The Earth is a fixed place traveling in space. • Human population has a limitless capacity to reproduce. • Therefore Nature must impose limits, and these will be starvation, war, famine and pestilence, according to Malthus.

  10. What was the Missing Element in Malthus? Same Problem 1970 • Technology

  11. Carrying Capacity • This is the total number of people the world can support. • But, the number changes with new inventions, such as crop genetics, or anything that grows more food. • So, is the carrying capacity of the earth limitless? • Will technology always save us?

  12. “Overpopulation” • If we say some place is “overpopulated” it has to be relative to something else. • An “overpopulated” place can stop being “overpopulated” if technology increases, for instance, food yields. • Is the Earth overpopulated? How would you tell? Chicago 1906 Is it Overpopulated?

  13. Overpopulation Immigration • First, has to be relative to your technological ability to squeeze life-support from your resource base. • Is also a matter of distribution—the population has greater and greater difficulty moving from dense areas to less-populated areas, especially if there is an international border between.

  14. Factors affecting Growth of Population. All these have changed Radically in the last 100 years • Infant mortality—the biggest killer in poor societies • Disease, particularly epidemics like cholera • The longevity, or age to which people expect to live • The fertility: how many children people have

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