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Environmental Science
Carl Mitchell

EESA01 Sept17, 2012 Jennifer Wu Population and Environmental Consequences Comprehension Objectives for Today’s Lecture • The scope of human population growth • The history of human population • Fundamentals of demography • The demographic transition • Factors that affect population growth • The effect of population, affluence and technology on the environment • The current effects of disease in controlling population growth Population: A root cause of environmental degradation? • Much of the environmental degradation in the world is due to: Population growth Wide misuse and overuse of resources by too many people. IPAT(S) Model • 1974: Paul Ehrlich and John Holdren • Total impact (I) on environment is a result of the interaction between population (P), affluence (A), technology (T), and sensitivity (S): Population = individuals need space and resources Affluence = greater per capita resource use Technology = increased exploitation of resources or ways of better dealing with our need for resources Sensitivity = how sensitive an area is to human pressure I=PxAxTxS • Impact is largely POLLUTION, RESOURCE DEPLETION, or both. The First Humans • Oldest known homonid (human-like) fossils: Ethiopia: 4.1 My. Bp Lucy Australopithecus afarensis Chad: ~7 My. bp? “Toumaï” Sahelanthropus tchadensis EESA01 Sept17, 2012 Jennifer Wu Doubling Time • The number of years it takes, given a specific rate of increase, for a number (such as population) to double. ln(2)´100 70 tD= = growthrate(%) growthrate(%) 1979 China growth rate = 2.8% (popl’n at time: 1B) Current global growth rate = 1.2% (now: ~6.9B) Current Canada growth rate (natural and net immigration together) = 0.9% (now: 33.5M) Global Population Growth IT TOOK MOST OF HUMAN HISTORY (UNTIL ABOUT 1800) FOR THE   GLOBAL POPULATION TO REACH 1 BILLION. 2 BILLION BY 1927. 3 BILLION BY 1960. WE HAVE DOUBLE OUR POPULATION SINCE 1966. 7 BILLION PEOPLE ANTICIPATED POPULATION BY 2011. DECLINED TO ~1.2%, WE ARE STILL GROWING AND EVEN A SMALL RATE WITH SUCH A LARGE POPULATION NUMBER IS SEVERELY COMPOUNDED OVER TIME (MUCH LIKE A NICE BANK ACCOUNT). Carrying Capacity • “The maximum population size of a species that a given environment can sustain.” • Limiting factors • Births ≈ deaths Earth’s carrying capacity? Between 10 million and 33 billion. Carrying Capacity Uncertainty EESA01 Sept17, 2012 Jennifer Wu 4 Distinct Increases in Carrying Capacity for Humans A. Progressive diffusion from original centres B. Surges in population: “technological change” “leaps” – “revolutions” Cultural Revolution during Paleolithic Period Cultural Revolution/Paleolithic Period: • Development of tools; stone, bone, wood (Note animal tool use – crows) • Omnivorous diet • Manipulation of fire • Development of speech and communication • Toolmaking: Ethiopia: 2.6 My bp Tanzania: 1.75 My bp • Little evidence of population at time. Agricultural Revolution Agricultural Revolution: • Start ~ 10-12,000 years bp • Transition from nomadic hunter-gatherer to settled farmer (environmental manipulation to meet needs) • Consequences: Reduction of area needed per person 500 X population density Excess of food production over minimum Whole population need not be in food production or acquisition Establishment of settlements Social structures – priests – accountants – salesmen “Fertile Crescent” – note soil salinization & collapse of society •
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