Lecture 19 - BIO220

5 billion with food consumption of canadaus but other

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Unformatted text preview: ople will be living • Current food production could support about 10 billion with food consumption of countries like India • About 2.5 billion with food consumption of Canada/U.S. • But other countries aspire to consume as we do! The Demographic Transition Model • Stage 1, pre industrial: birth and death rates both high, r near zero Not really growing • Stage 2: death rates drop (sanitation, vaccination, etc.), but birth rates stay high; population booms • Stage 3: birth rates fall (contraception, changing values, later marriage), growth rate slows • Stage 4: birth and death rates equilibrate, r near zero again -We have maxed out food production for the globe. How many people can the world support based on the production of grain, protein etc. -If we all consumed food and calories similar to India: K=10billion -If we all eat like US: K=2.5 billion (w. current agricultural production) -Vast majority of the world aspires to have a diet like the US -If we can understand social/cultural processes, we can make better estimates a bout growth rate -We can also implicate better measures 3 20/03/2013 Demographic transition in Sweden Graphical version of classic demographic transition model Post WWI baby boom But is there any reason why one would expect fertility and mortality to equilibrate exactly? Spikes in death rates = epidemics, episodes of famine Why does B rate = D rate? -Does it have to happen? <= Changes in age distribution have profound consequences for economy, social structure: “dependency ratios” Stage 1: Pop not growing. R=0 Stage 2: Majority still young, some starting to age Stage 3: More people becoming older Stage 4: Pyramid turns into a rectangle. Even in both cohorts Post WWII baby boom Baby boom “echo” Influenza epidemic of 1919 DEPENDENCY RATIO: -Majority people old, fewer young -Economic consequences: pension p lans: set up when there w...
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