Midterm Envi

• Population growth

  Already slowing down, reaching equilibrium remains a difficult but vital question
• Causes and consequences of population growth

  Argued since the Industrial Revolution
• An Essay on the Principle of Population was written by Thomas Malthus


  1798
• Rational (in Malthusian terms)


  Human populations limited by disease, famine, or social constraints that compel people to reduce birth rates
• Rational (in Karl Marx's terms)

  Population growth results from poverty, resource depletion, pollution, and social ills
• Marx and Malthus developed theories about human population growth
• Some believe we may have surpassed the earth's carrying capacity
• Estimates suggest the earth can sustain a median population of 10-12 billion
• Technology increases carrying capacity for humans
• Food supplies have increased faster than population growth since Malthus's time
• Progress in various fields has made it possible to support more people per unit area
• Ecological footprint measures the impact of human activities in terms of biologically productive land and water required
• Population growth could bring benefits
• No evidence shows that pollution, crime, unemployment, crowding, loss of species, or resource limitations will worsen with population growth
• People are considered the "ULTIMATE RESOURCE"
• An increase in population would stimulate technologies to increase food production
• Birth rate is relatively higher than mortality rate, resulting in a net increase in population
• PAST AND CURRENT POPULATION GROWTH ARE VERY DIFFERENT
• Birth rate is relatively higher than mortality rate, with nearly 5 children being added every second and 1 or 2 people dying
• The world adds around 75 million more people at a rate of 1.1 percent per year
• The world's largest countries in 2010 and 2050

  • China, India, U.S., Indonesia, Brazil, Pakistan, Bangladesh, Nigeria, Russia, Congo
• China was the most populous country throughout the twentieth century; India is expected to pass China in the twenty-first century. Nigeria is forecast to have 299 million residents in 2050
• Factors in determining human population growth
• Fecundity


  The physical ability to reproduce
• Fertility


  The actual production of offspring
• Crude birth rate

  The number of births in a year per thousand persons
• Zero population growth (ZPG) occurs when births plus immigration equal deaths plus emigration
• Total fertility rate


  The number of children born to an average woman in a population during her entire reproductive life
• In most tribal or traditional societies, food shortages, health problems, and cultural practices limit total fertility to about 6 or 7 children per woman
• Fertility rates have declined dramatically in every region of the world except Africa over the past 50 years
• The average family size in Mexico decreased from 7 children in 1975 to 2.3 children in 2010
• In Iran, total fertility fell from 6.5 in 1975 to 2.04 in 2010
• China's one-child-per-family policy decreased the fertility rate from 6 in 1970 to 1.7 in 2010
• Crude death rates are expressed in terms of the number of deaths per thousand persons in any given year
• Countries in Africa with limited healthcare and sanitation may have mortality rates of 20 or more per 1,000 people
• Wealthier countries generally have mortality rates around 10 per 1,000
• Rapidly growing, developing countries like Brazil often have lower crude death rates than more developed, slowly growing countries
• The number of deaths in a population is sensitive to the population's age structure
• Life expectancy is the average age that a newborn infant can be expected to attain in any given society
• Life expectancy rose from about 40 to 67.2 years over the past 100 years