Presentation on theme: "Human population growth"— Presentation transcript:
1 Human population growth DemographicsHuman population growth
2 World population has risen sharply Global human population was <1 billion in 1800.Population has doubled just since 1963.We add 2.5 people every second (79 million/year).
3 Birth and Death Rates, Worldwide Rates of birth, death, and natural increase per 1,000 populationNatural IncreaseSource: United Nations, World Population Prospects: The 2004 Revision, 2005.
4 Death Rates Have Gone Down World population growth in past 100 years is due to a decline in death ratesBetter medicineReliable foodGood nutritionBetter sanitationSafer water
5 Increasing our carrying capacity Technology has allowed us to raise Earth’s carrying capacity for our species time and again.Tool-making, agriculture, and industrialization each enabled humans to sustain greater populations.
6 Age structure can influence population growth rates.
7 Age structure: Age pyramids Canada (left) has a much slower growing population than does Madagascar (right).
8 Age structure: “Graying populations” Demographers project that China’s population will become older over the next two decades.
9 Age structure: “Baby booms” The United States’ “baby boom” is evident in age bracket 40–50. U.S. age structure will change as baby boomers grow older.
10 Demography Demography is the study of human populations. Human populations exhibit the same fundamental characteristics as do populations of all other organisms.
11 Demographic transition theory Demographic transition = model of economic and cultural change to explain declining death rates, declining birth rates, and rising life expectancies in Western nations as they became industrializedProposed by F. Notestein in the 1940s-1950s
13 Demographic transition: Stages Pre-industrial stage: high death rates and high birth ratesTransitional stage: death rates fall due to rising food production and better medical care. Birth rates remain high, so population surges.Industrial stage: birth rates fall, as women are employed and as children become less economically useful in an urban setting. Population growth rate declines.Post-industrial stage: birth and death rates remain low and stable; society enjoys fruits of industrialization without threat of runaway population growth.
14 Population size: Future projections Demographers project population growth trends to estimate future population sizes.Different fertility rate scenarios predict global population sizes in 2050 of 7.4 billion, 8.9 billion, or 10.6 billion.All these projections assume fertility rates below today’s; at today’s rate, the population would reach 12.8 billion.
15 Population density and distribution Humans are unevenly distributed, living at different densities from region to region.
16 95% of all population growth is taking place in Developing Countries BillionsLess Developed RegionsMore Developed RegionsSource: United Nations, World Population Prospects: The 2004 Revision (medium scenario), 2005.
17 Factors affecting population growth rates Population growth depends on rates ofBirthDeathImmigrationEmigrationPOPULATION GROWTH RATE =(birth rate + immigration rate) – (death rate + emigration rate)DOUBLING TIME = 70/Population Growth RateNATURAL RATE OF POPULATION CHANGE =Change due to birth and death rates aloneexcluding migrationIs often expressed in % per year
18 Migration can have environmental effects Immigration and emigration play large roles today.Refugees from the 1994 Rwandan genocide endured great hardship, and deforested large areas near refugee camps.
19 Global growth rates have fallen The annual growth rate of the world population has declined since the 1960s.(But the population size is still rising!)
20 Fertility rates affect population growth rates Total fertility rate (TFR) = average number of children born per woman during her lifetimeReplacement fertility = the TFR that keeps population size stableFor humans, replacement fertility is about 2.1
21 Total fertility rates by region African nations have the highest TFRs. European nations have the lowest TFRs.
22 SINGLE MOST IMPORTANT FACTOR THE SOCIAL AND ECONOMIC STATUS OF WOMEN
23 Educational Opportunity & Fertility Women with more education marry later and have fewer children
24 Female education and TFR Female literacy and school enrollment are correlated with total fertility rate:More-educated women have fewer children.
25 FAMILY PLANNING SERVICES Reduced Fertility Rate does not happen without access to servicesDoes not force limited family sizesPromotes small family as acceptable & desirableprovides info and access to contraceptives
26 Family planning and TFR Nations that invested in family planning (green) reduced TFRs more than similar nations that did not (red).Figure 7.17a
27 Key Factors that Reduce Population Growth: Investments in Education and Health Status of womenGeneral educationEmployment opportunities, economic securityHealth and nutritional status (including pre- and post-natal care)UrbanizationFamily planning methodsAccess to family planning optionsAffordability of family planningComfort with family planning methodsAge at first birthSpacing between childrenDecrease consumption
28 Affluence and the environment Poverty can lead to environmental degradation…BUTWealth and resource consumption can produce even more severe and far-reaching environmental impacts.ONE American causes greater impact & more resource depletion than 12 people from developing countries
29 Make make 75% of world’s pollution Born ConsumersHighly Developed Nations = 20% of world’s population but use:86% of aluminum76% of timber harvested68% of energy produced61% of meat eaten42% of fresh water consumedMake make 75% of world’s pollution
30 The wealth gapResidents of developed nations have larger houses, more possessions, and more money than residents of developing nations.The richest 20% of the world’s people consumes 86% of its resources, and has >80 times the income of the poorest 20%.
31 Ecological Footprint Ecological Footprint cumulative amount of Earth’s surface area required to provide the raw materials a person or a population consumes and to dispose of or recycle the waste that is producedshows the area of the earth that is needed to supply all the resources to support a standard of livingcan be shown for individuals or for entire countries
32 Ecological footprints Residents of some countries consume more resources—and thus use more land—than residents of others.Shown are ecological footprints of an average citizen from various nations.
35 Conclusions: Challenges Human population is rising by 79 million people annually.Many more people are born into poverty than into wealth.Rich and poor nations are divided by a “wealth gap.”HIV/AIDS is taking a heavy toll.Population growth has severe environmental effects.
36 Conclusions: Solutions Expanding women’s rights is crucial to encourage the demographic transition.Health and reproductive education and counseling can reduce fertility rates.Education, medicine, and policies can lessen the toll of HIV/AIDS.New “green” technologies can help reduce population growth’s environmental impacts.