Human Population Growth What the numbers tell us

Types of Growth F Growth calculated as b-d total F Positive growth b>de.g = 20% total 100 F Negative growth b<de.g = - 20% total 100 F Zero growth b=de.g = 0% total 100 F Slow growth b=de.g = 2% total 100

F Population Growth Graphs Time # J curve - implies exponential growth Carrying capacity - the maximum number of individuals their environment can sustain in the long term Limiting Factors - conditions which determine the carrying capacity Density dependant density independant

Time # ?? How do you determine carrying capacity - very difficult to do Population crash - when a population size exceeds the Carrying capacity, the size will decrease.

Time # ?? S curve - zero or very slow growth. Provided a population can turn a J curve into an S curve before reaching carrying capacity, a crash will be averted

Historical growth rates = from a high of <2% in 1950’s to 1.7% currently Fertility rates - estimates of average number of children by one woman in her childbearing years Data from children/woman worldwide 3.8 “in LDC’s 1.9 “ in MDC’s

TimeEstimated Human Pop. SizeDoubling Time (years) M B B B B24 years to rise by 2 B 20238B 16B?????

TIME BCAD || 1000 | 2000 # ?? GROWTH = B-D TOTAL

FACTORS AFFECTING FERTILITY F Education F Affluence F Economics –Use of children as labor –Old age security –Cost F Infant Mortality Rate –Replacement children F Status of Women F Reproductive Technologies F Cultural Views F Religious Views –UN Population Conference on Population and Development; Cairo Egypt, September 1995

F Birth Control –Africa <10% –Central and South America ~40% –Asia ~65% F National Programs to Reduce Birthrates –These require changes in attitude, education and knowledge to do so, and the ability to afford these means –Examples : u India u China u Thailand u Canada & Germany

F Death Variable F Lifespans increasing!!!!!!!! Better nutrition; sanitation, hygiene, increase in food production, medical technologies (vaccinations, antibiotics, surgical interventions, genetic therapies and advances, etc) F Overall life expectancies from years old in MDC’s 62 in LDC’s 47 in poorest countries F Japan hold highest life expectancy rank, Sweden is next F Leading causes of death: Heart Problems F Can We Reduce this Variable?????? –Moral issues say no u Euthanasia –Modern medicine says no –Human Genome Project??

Age Structure Pyramids F Demographers tool to predict future population trends F Rapid Growth - very bottom heavy F Slow Growth - more uniform in size F Zero Growth - smaller at bottom than in middle

Tonight’s Video - the Population Bomb F Paul Ehrlich vs Julian Simon F Biologists vs Economists F IPAT equation = I impact of any given population P size of that population + A affluence; ability to consume + T technology; environmental cost