World Population: Growth & Trends

Transcription

1 World Population: Growth & Trends

2 Carrying Capacity Physical carrying capacity = packing density, limited only by space and resources Cultural carrying capacity is always less Still there is a large difference of opinion regarding how many people the earth can support. Accepted range for K is billion people

3 Factors affecting Growth Rate Growth rate = Birth Rate - Death Rate 1.1% = 1.9% - 0.8% (as of 2012) Of these the Birth Rate is the most important contributor, specifically the Fertility Rate (#children/woman) Why? Because death rates have stabilized...

4 World Population Growth

5 Population (in Billions) World Population: 7.3 billion As of Sept., 2014 World Population ( ) Year (AD) (Super)exponential growth

6 Likely population by 2050: 9 billion

7 Population Pyramid Age Population in age class

8 World Population Problems Nature of the World Population Problem Stable population for 8,000 years Survival precarious for most people Since 1650 there has been rapid population growth

9 Population variables Population increases are a function of three variables, i.e. fertility, mortality and migration Population formula: Population (now) = Population (then) + (births-deaths) +/- Migration

10 World Population Growth 8,000 BC to 1650 AD = 500 million 1650 AD to 2000 AD = 5.6 billion 50,000 new mouths to feed every year in first period 50,000 new mouths to feed every 6 minutes today. 90 million people added every year today

11 Four stages of DT 1. The Preindustrial Stage when there is little population growth because harse social conditions lead to both high death and high birth rates. 2. The Transitional Stage, when industrialization begins and health care improves, resulting in lowered death rates, but birth rates remain high. Most of the developing world here. 3. The Industrial Stage, when the birth rate drops due to modernization (and its accompanying social changes). Many developed countries and a few developing countries here. 4. Finally, the Postindustrial Stage is recognized by further reductions in birth rates, approaching or even below zero population growth. Approximately 13% of the world population (mostly European countries) is in this stage. A complete DT exhibits both declining birth and death rates

12 Population Pyramids for the four demographic transition phases

13 Why Population is so important Thomas Malthus (1798) Organism populations increase exponentially, whereas the environment is fixed (actually decreases). Factually correct, but a complex problem... Modern example: high populations AND high quality of life

14 Validity of Malthus Predictions Malthus proved to be poor prophet in 18 th and 19 th C Famine, disease, war did not result in decreased world population Was Malthus premature? Paul Erlich s Population Bomb (neo-malthusian position) vs. Julian Simon s Population as the Ultimate Resource. (cornucopian position)

15 Neo-Malthusian position Population growth straining the world s resources Destruction of forests for development and/or food production Energy and mineral consumption taxes resources Over-fishing Widening gap between rich and poor Inadequate development, refugee problems, donor fatigue Belief in environmental responsibility leading to sustainable growth

16 Cornucopian position Life expectancy doubled in 20 th C (30yrs to 60 yrs) Global health and productivity expanding Overpopulation is scare talk of environmentalists The real issue of poverty not breeding Technology will solve all human problems Population growth creates jobs, opens markets, expands opportunities Ecologists want sustainability; cornucopian economists want economic growth, exploitation of markets and resources

17 Thinking about this issue

18 Take away concepts Why is population growth so central to environmental problems? What is the current population? What will it be in 2050? What factors affect population growth rates? How do growth rate compare in developed vs. developing countries? What is a "demographic transition? What are its stages? Interpreting Population Pyramids. Understanding modern demographic trends.

19 Reducing population growth Successful efforts to reduce population growth by Japan, China, South Korea, Thailand, and Iran. These countries were able to achieve replacement-level fertility (enough children born to replace death of parents) within years - this is good news. Key Factors were: Invest in Family Planning Reduce poverty Elevate the status of women

20 Views from Joel Cohen s 1995 book How Many People Can the Earth Support? 1. Make a bigger pie: Increase human productive capacities through technology and innovation. 2. Put fewer forks on the table: Reduce numbers and expectations of people through such means as family planning and vegetarian diets. 3. Teach better manners: Change the terms of people s interactions through improved planning and government to enhance social justice.

21 Questions