Ch 24 Human OverPopulation And overconsumption Rapid population growth What kind of growth? 2 Population Growth The Logistic Growth Model Two models Exponential growth The larger a population becomes, the faster it grows Logistic growth Limited growth In reality, the environment is limited Limiting factors Food Space Seal hunting was controlled Population growth over human history The most populous nations Slow growth until 1700s Industrial revolution Better farming techniques Better storage of food Improved sanitation Advances in medicine Exponential growth Due to drop in death rate China (20%) India (17%) EU (7.5%) US (4.6%) 2009 http://www.poodwaddle.com/worldclock.swf 5
Population trends Today s population is 7 billion And growing By 2050, the population will increase by 2-3 billion people Most growth will occur in developing countries Birth rates (births/1000 people) 23 12 7 8 DVD: World in the Balance the population paradox Differences in population trends in developing and industrialized nations India Japan US (4:23 36:39 Kenya 45:40) Population trends in India How do birth rates vary between northern and southern India? What factors promote high birth rates? What cultural factors influence population growth? What are some of the consequences of continued population growth? Population trends in Japan What has happened to the population in Japan? What factors contribute to the low birth rate? What are some of the consequences of an aging population? Population trends in the US What is happening to the US population? What are some of the consequences of these changes?
The BIG question Fresh water is a limited resource When the population stabilizes, it will be higher than it is now. Will we have enough resources for everyone? It covers most of the planet, but just 3% is fresh water Food Fresh water Energy 14 Conserving water Agriculture is one of the biggest users of water Conservation: By 2025, 2/3 of world s population may face serious water shortages Global warming How is global warming affecting living organisms? What can we do about it? 70% of freshwater is used to irrigate crops Plant drought- and salttolerant crops Use drip irrigation Reuse water What is the evidence for global warming?
What is the major source of CO2 released by human activities? Why is the earth warming up? Greenhouse gases in atmosphere Solar energy passes through Radiant heat is trapped Greenhouse gases (CO2, methane, water vapor) trap heat in the atmosphere. Burning fossil fuels releases huge amounts of CO2 into the atmosphere The Greenhouse Effect Burning carbon-containing fossil fuels Global warming 101 Natl Geo 3:04 http://www.youtube.com/watch?v=ojabatjcugs Sea level rise in the Bay area Likely effects of global warming Increasing drought Decreasing crop productivity Melting of ice in glaciers and the polar ice caps, Rising sea level Scientists predict that sea level could rise 3 feet by 2100 Flooding We need to reduce our resource consumption We in the industrialized countries, with 20% of world population, use 86% of the world s resources The other 80% of the world s population must share the remaining 14% of the resources 13 of 20 largest cities in world are located at sea level As are hospitals and water-treatment plants What can we do about global warming? R E DUC E CO2 EM I SSI O N S
How can we do it? Renewable Energy Sources Phase-out coal Increase energy efficiency Needed: Stronger emission standards and a carbon tax Use renewable energy Solar, wind, geothermal Improve the electrical grid More R&D Next generation of nuclear reactors (reduced waste) Carbon capture and sequestration Top candidates Solar power Wind power Nuclear power Safety issues Waste disposal YOU can make a difference Conserve energy: Walk, bike, use public transit, or carpool Make sure your tires are fully inflated and your car tuned up Lower your water heater and home thermostats Only run your dishwasher with full loads Reduce your shower length and temperature Turn off lights when leaving a room Use recycled paper Reuse or recycle as much as you can