Population

2. Population The power of population is infinitely greater than the power in the earth to produce subsistence for man. – Malthus - 1798 Since last class – world population increased by ~ 1,090,000

3. Rule of thumb for exponential growth Amount doubles in: t = 70/growth rate (%) If population is growing at 2%/year, it doubles in 35 years… P(t) = (1 + g)n p(0) ~ en g p(0)

4. Linear vs. exponential growth Both curves have same increase in first year

5. Carrying Capacity How many people can the Earth hold? Page 5

6. Thomas Malthus • 1798 Essay on the Principle of Population • Population grows exponentially • Food grows linearly • Eventually there will be a problem • Leading to misery, vice, and poverty • Underestimated human ability to increase food production… • But…

7. Population Density (people/km2) • 1 Monaco21,781 • 2 Singapore6,814 • 3 Vatican City1,877 • 4 Bahrain1,454 • 5 Malta1,309 • 6 Bangladesh 1,211 • 172 United States 31 • NY City 10,606 • Manhattan 27,490 • World 13 ?

8. Population Density • To get 1pers/m2 NYC would only have to go up a factor of 100 • Is the world population doubling rate steady?

9. Population • When I was your age – the world’s population was ~3 billion • When you are my age – the world’s population will be 9 billion • How many people can the earth hold - “carrying capacity”? • The surface area of the earth is ~5 x 1014m2 - but 2/3 is ocean so let’s say there are 2 x 1014m2 available. • So there is 1 person in 2 x 1014 / 7 x 109 = ~3000 m2 over the land area of the earth – 1pers/.003km2 or ~35 people/km2 • This room has 1pers/m2 – that looks like enough for me… • How long will it take for the population to go up by a factor of 3000 to 27 trillion (2x1013) assuming a 35 year doubling period? • Every doubling period the pop. goes up 2 so after m periods the population is 2m higher. • 211 is 2048 – 212 is 4096 – so it will take ~11.5*35 = ~400 years

10. Population • Another way – energy • To survive we need about 2000 kcal – 8400kJ of food/day • The solar energy (used to grow food) is about 8x1018kJ/day • So if we use all solar energy to produce just food 100% efficiency – we can support ~1015 people

11. Estimates of Human Population

12. Estimates of Human Population Green revolution Industrial revolution Fire, tool-making

13. UN Population Scenarios

14. Converting solar energy into food

15. The Trophic Pyramid • Trophic (feeding order) Pyramid

16. The Trophic Pyramid • Why so little passedon?

17. The Trophic Pyramid

18. The Trophic Pyramid • Photosynthesis is about 5% efficient in turning sunlight to sugars • In the US about 1/3 are primary consumers and 2/3 are either secondary or tertiary so take an average of 5% • So take this and we get 5 x10-2 x 5 x10-2 = 2.5x10-3 as the fraction of energy available for people and get • ~1014 people x 2.5x10-3 = 2.5 x 1012 =250 billion people

19. Arable land • Only 25% of the Earth’s land is capable of sustaining crops • Its currently expensive to increase the amount of arable land • Israel did it, but it was expensive. Israel's land primarily consisted of desert until the construction of desalination plants along the country's coast.

20. Another calculation • Need to share some food with animals that aren’t directly in our food chain • Say another factor of 2 • We have a factor of 4 from arable fraction and another factor of 2 from sharing • So we take our 250 billion people and cut it down by a factor of 8 and we get to 30 billion • These represent some sort of absolute upper limits • With a 35 year doubling we would hit this limit in your lifetime…

21. Where the People Are

22. How Many Humans Have Ever Lived? • Answer depends entirely on when we start counting “humans” • Lower limit: assume two “modern Homo sapien sapiens” in 50,000 BC • 50 billion born before 1 AD • 60 billion born after 1 AD, of which • 6.9 billion alive today

24. Area Proportional to Population

25. Area Proportional to Population

27. Projections Trending Downward

28. Fertility Declining Faster Than Expected

29. Infant Mortality Rates

30. Life Expectancy: UN Medium

31. Life Expectancy Increasing

32. Population Pyramids What are these bumps?

33. Population Pyramids

34. What Determines Carrying Capacity? • Standard of living (what kind of life?) • Technology • Food and fiber (land, nutrients, fisheries) • Water • Energy (fossil, nuclear, solar?) • Metals, minerals, other resources • Waste assimilation • Disease • War

35. Estimates of Carrying Capacity

36. Economic growth Q. Can we have economic growth forever? - most economists see 3% growth as healthy “any sustained period of GDP growth below 2.5% is a recipe for rising unemployment and sluggish wage growth.” Economic Policy Institute, April 2008. 3% growth would correspond to a 23 year doubling time Q. How do we grow without consuming more resources? “Sustainable growth” - an oxymoron

37. US GDP Growth last quarter?China GDP Growth last quarter? Page 38

38. US GDP Growth last quarter? 1%China GDP Growth last quarter? Page 39

39. US GDP Growth last quarter? 1%China GDP Growth last quarter? 9.5% Page 40

40. Tragedy of the Commons • Garrett Hardin 1968 • Article is on ELMS • A commons is an open spaceavailable to all • Hypothetical case of 10 dairy farmers using the land • In hard times everyone has a few cows and there is plenty of grass for all • As things improve we assume the that eventually we get 20 cows each (total 200 cows) and we have reached the carrying capacity of the land

41. Tragedy of the Commons • What should a rational farmer do? • If he adds a cow he gets the benefit of another cow • However all the cows including his 21 now only get 200/201 (99.5%) of the nutrition it needs produce a full amount of milk • Mathematically lets say his benefit is +1 from the extra cow but each cow loses about 0.5% so he loses ~10% of one cow so his net profit from adding the cow is 9/10 of a cow • So he should do it • And so should everyone else • What happens next?

43. How do we deal with T.o.t.C? Privatization If I own the land, it is in my interest to adjust the number of cows to prevent catastrophe Regulation An organization (usually governmental) set rules to make sure catastrophe does not happen

44. G. Hardin - 1998 • "A 'managed commons' describes either socialism or the privatism of free enterprise. Either one may work; either one may fail: 'The devil is in the details.' But with an unmanaged commons, you can forget about the devil: As overuse of resources reduces carrying capacity, ruin is inevitable."

45. Crticisms of T.o.t.C? Often used as an excuse to argue for privatization Simplifies individual’s concept of self-interest to an extreme Used as an excuse for “excessive” regulation Neglects innovation that “expands” the common

46. 2009 Nobel Prize in Economics ElinorOstrom “for her analysis of economic governance, especially the commons.” Challenged the conventional wisdom by demonstrating how local property can be successfully managed by local commons without any regulation by central authorities or privatization. Page 47

47. Larry David explains Elinor Ostrom's work Page 48

48. Tragedy of the Commons as the Earth • Uncontrolled human population growth leading to overpopulation. • Water - Water pollution, Water crisis of over-extraction of groundwater and wasting water due to overirrigation. • Forests - Frontier logging of old growth forest and slash and burn. • Energy resources and climate - Burning of fossil fuels and consequential global warming • Animals - Habitat destruction and poaching leading to mass extinction. • Oceans – Overfishing, depletion of populations

49. TANSTAAFL • There ain’t no such thing as afree lunch • Every thing has a cost • This cost may not be obvious at first • Ozone • Industrialization • Pollution • Energy usage • Cell phones • Bad driving • Nuclear Energy • Waste • Proliferation