How Many People Can the Earth Support?

2. How Many People Can the Earth Support? We do not know how long we can continue increasing the earth’s carrying capacity for humans without seriously degrading the life-support system for humans and many other species.

3. Environmental science is the study of how the natural world works, and what is happening to it as the human population expands. It includes all of the natural sciences and sometimes economics and a few other social sciences. • Major topics can be boiled down to: • Human population • Energy & all implications of its use including air pollution • Resources-biological, water, mineral

4. What is environmental science? Knowing where your water/food/energy come from and where your waste goes

5. The single driving mechanism for all the environmental problems we face in the world today may be exponential growth.

6. Key Concepts • Humans are subject to natural laws and ecological processes such as limiting factors. • Significant differences in developed vs. developing worlds • Unlimited use of natural resources is unsustainable • There are a number of tools to understand populations project future outcomes

7. There are more people living on Earth today than ever before in human history. Both the number of people and the amount of overall consumption exert an impact on the environment. Wednesday Jan26

8. What is Earth’s Population Capacity

9. Population Trends over 200 yrs

10. Today 6.6B www.prb.org

11. What Factors Influence the Size of the Human Population? Population size increases because of births and immigration and decreases through deaths and emigration. The average number of children born to women in a population (total fertility rate) is the key factor that determines population size.

12. Population Size • Natality • Number of individuals added through reproduction • Crude Birth Rate - Births per 1000 • Total Fertility Rate – Average number of children born alive per woman in her lifetime • Mortality • Number of individuals removed through death • Crude Death Rate Deaths per 1000

13. Calculating Population Change, = (Births + Immigration) – ( Deaths + Emmigration)

14. Demographic TransitionCalculating the % increase or decrease of a population (CBR – CDR)/10 = Rate of increase or decrease in population per 1,000 per year Number of births or deaths/1000 so countries can be compared. Crude because no consideration of who is old or young

15. Calculating Doubling Times 70/Rate of Increase = Doubling Time The world rate of population increase is 1%. How long would it take to double the population? 70 years

16. Calculating % increase (Fertility Rates) and Doubling Times: Practice Calculate the Rates of increase and doubling times

17. Calculating % increase (Fertility Rates) and Doubling Times: Practice

18. End of WWII Depression Demographic Transition Baby Boom…………….. Echo Baby Boom…………

19. Age Structure Diagrams Positive Growth Zero Growth Negative Growth (ZPG) Pyramid Shape Vertical Edges Inverted Pyramid

20. Population Profiles of the United States

22. Human Population Growth Continues but It Is Unevenly Distributed Population growth in developing countries is increasing 15 times faster than developed countries By 2050, 97% of growth will be in developing countries Should the optimum sustainable population be based on cultural carrying capacity?

23. Major concers that growing populations cause increased environmental stresses? Infectious diseases Biodiversity losses Water shortages Traffic congestion Pollution of the seas Climate change Population Capacity 3 BBC Water Use

24. What is Earth’s Population Capacity • Population Capacity 2 • Population Capacity 3 Water Use • Population Capacity 4 Competition for scarce resources • Population Capacity 5 today’s population • Population Capacity 6 Future Efforts

25. Women Having Fewer Babies but Not Few Enough to Stabilize the World’s Population Fertility rate Replacement-level fertility rate Total fertility rate (TFR)

26. Several Factors Affect Death Rates (1) Life expectancy & Infant mortality rate Why are people living longer and fewer infants dying? Increased food supply and distribution Better nutrition Medical advances Improved sanitation

27. Several Factors Affect Death Rates (2) U.S. infant mortality rate high due to Inadequate health care for poor women during pregnancy and their infants Drug addiction among pregnant women High birth rate among teenagers

28. Migration Affects an Area’s Population Size Economic improvement Religious freedom Political freedom Wars Environmental refugees

29. No one knows if the population on Earth will double again. Although the number of additional people on Earth continues to increase each year, the rate at which the population is growing each year, the growth rate, is slowing.

30. Infant Mortality:number of deaths by age 1 per 1000 live births in the populationUSA Average 6.6Sweden 2.4France 3.6Afghanistan 166

31. Infant Mortality (all values from 2005)USA Average 6.6 African-Americans 13.6 Native Americans 8.9Washington, D.C. 11.4Mississippi 10.5Louisiana 9.8Utah 4.8New Hampshire 3.8Singapore 2.3Sweden 3.1Bolivia 54Burundi 106Angola 188

32. Age Structure • The age structure of a population is usually shown graphically • The population is usually divided up into prereproductives, reproductives and postreproductives • The age structure of a population dictates whether is will grow, shrink, or stay the same size

37. Age Structure Diagrams Positive Growth Zero Growth Negative Growth (ZPG) Pyramid Shape Vertical Edges Inverted Pyramid

38. Disparities • Developed countries • 16% of the world’s population • Control 81% of the world’s wealth • Low-income developing countries • 41% of the world’s population • Control 3.4% of the world’s gross national income • Difference in per capita income: 62 to 1!

39. Population Increase in Developed and Developing Countries

40. Population Data for Selected Countries (Table 5-3)

41. Different Populations, Different Problems • Human pressure on the environment caused by three factors • Population size • Affluence • Technology

42. Ecological Footprints by World Region • The average American places at least 20 times the demand on Earth’s resources as does an average person in Bangladesh Fig. 5.7 here

43. Global Conditions for a Sustainable Population • Lower fertility rates (stabilize population) • Consumption must decrease • Protect the environment (stewardly action must increase)

44. Consequences of Population Growth and Affluence • The developing countries • Affluence

45. Developing or Developed Nations? • High fertility rates • High consumptive lifestyles: use 80% of world’s wealth • Intense poverty • Eat high on the food chain

46. Developing or Developed Nations? • Long doubling times • High environmental degradation • Twenty percent of the world’s population

47. Basic Human Needs • Drinkable Water • Edible Food • Safe Housing • Health Care • An Education • A Job

48. Growing Cities

49. Consequences of Exploding Populations in the Developing World

50. Consequences of Exploding Populations deforestation resource depletion loss of agricultural land biodiversity disease pest resistance population migration irrigation wetlands MORE More Population Causes LESS