© 2011 Pearson Education, Inc. CHAPTER 8 The Human Population

© 2011 Pearson Education, Inc. World population over the centuries

© 2011 Pearson Education, Inc. How many people can the Earth support? The number of people the Earth can support depends on the living standard we are willing to accept Many more people can be supported if we don’t eat meat, don’t travel, don’t heat or A/C our homes, etc. For all 7 Billion of us to enjoy a 21 st century American way of life, we would need many more Earths! So the real human carrying capacity is unknown. Your text suggests 7.7 Billion.

© 2011 Pearson Education, Inc. How have we gotten to 7 Billion?

© 2011 Pearson Education, Inc. The Agricultural Revolution Agriculture began 10,000-12,000 years ago. Better, more reliable nutrition meant less starvation and better resistance to infection. More people survived and reproduced. They needed more children to help on the farms.

© 2011 Pearson Education, Inc. The Industrial Revolution Began in 1800s with coal and then the steam engine Coal, oil, and natural gas let people do much more work than by human or animal power Cars, planes, cranes, bulldozers, huge fishing boats This easy energy lets people do more work, but it has also produced pollution and allowed resource exploitation

© 2011 Pearson Education, Inc. The medical revolution Before the early 1800s, human populations grew slowly and fluctuated Diseases (smallpox, diphtheria, measles, scarlet fever) hit infants/children hardest Epidemics (e.g., cholera, black plague) killed millions So high reproductive rates were offset by high death rates (mainly from diseases), resulting in a low population growth rate

© 2011 Pearson Education, Inc. Many diseases were vanquished 1797 Edward Jenner produced the first reliable vaccine 1800s Louis Pasteur showed that many diseases were caused by specific infectious agents (bacteria, viruses, fungi) & transmitted via water, food, insects, rodents Spectacular decreases in child and infant mortality boosted population growth Vaccinations Cities treating sewage and drinking water Penicillin (and other antibiotics) starting in late1940s Nutritional improvements Availability of contraceptives in developed nations.

© 2011 Pearson Education, Inc. Developed vs. developing countries Developed countries: high-income, industrialized nations. The U.S., U.K., Canada, Japan, Australia, Germany, Sweden, etc. Developing countries: most low-income nations. Afghanistan, India, Iraq, Iran, Haiti, many others. China and India are transitioning, because of a rising middle class in China and India. There is disparity of wealth between countries.

© 2011 Pearson Education, Inc. Fertility rates Total fertility rate (TFR) is the number of children the average woman will have during her lifetime. TFR has dropped worldwide, to 2.6 now. In developed countries, the TFR averages 1.6 The U.S. : TFR ~2.0 In developing countries, the TFR averages 2.8 These populations will likely continue growing It is projected that 90% of all people will live in developing nations by 2075

© 2011 Pearson Education, Inc. Total fertility rate, United States,

© 2011 Pearson Education, Inc. Projecting future populations: a developed country (here, Italy).

© 2011 Pearson Education, Inc. Projecting future populations for developing countries (Burkina Faso, for ex.)

© 2011 Pearson Education, Inc. Comparing projected populations

© 2011 Pearson Education, Inc. Population momentum Population momentum: the tendency of a population to increase for a while, even though TFR is reduced to 2 or less. This is analogous to hitting the brakes when the light turns red. You can’t stop instantly. Age structure of the population is key: The more young people you have, the more reproduction. A stable population will be obtained only when the population has been at replacement level fertility (TFR=2.0) for decades!

© 2011 Pearson Education, Inc. The demographic transition Modernization results in lower death rates, better health care, declining fertility rates Undeveloped societies have stable populations High birth rates and infant and childhood mortality rates Developed societies have stable populations Low birth rates and infant and childhood mortality rates Demographic transition: a shift in birth and death rates from the primitive to the modern condition in industrialized societies

© 2011 Pearson Education, Inc. Birth and death rates Crude birth rate (CBR): the number of births per thousand people per year Crude death rate (CDR): number of deaths per thousand people per year No consideration for age, gender CBR – CDR = natural increase (decrease) per 1,000 per year Zero-growth occurs when CBR = CDR With no net migration

© 2011 Pearson Education, Inc. Epidemiologic transition Most of human history had high crude death rates Death rates in Europe and North America gradually declined by the middle 1800s At present, most mortality is from cancer, cardiovascular disease, and other degenerative diseases

© 2011 Pearson Education, Inc. Phases of the demographic transition Phase I: primitive stability High CBR is offset by high CDR Phase II: epidemiologic transition. Better health care means a declining CDR But a high CBR results in rapid population growth Phase III: Fertility rates decline Population growth is still significant Phase IV: modern stability is reached CDR and CBR are both low

© 2011 Pearson Education, Inc. The demographic transition