The Human Population Think of the earth as a living organism that is being attacked by billions of bacteria whose numbers double every forty years. Either the …bacteria dies, or both die.  - Gore Vidal

Planet Earth: Population 7 Billion The evolution of Homo sapiens and a total population of about 2 billion took about 200,000 years In 2015, the World population reached 7.3 billion people It’s estimated that there will be 2.5 billion more people by 2050 Are there too many people already? Will technological advances overcome environmental resistance that populations face? Should populations be controlled/limited?

Early Human History During the earliest parts of human history, our population survived as hunter-gatherers. The population during this time was low; estimated to be in the thousands. Like other species, population size was limited by environmental resistance factors, such as competition for food and water, predators, and disease.

At some point, estimated to be about 130,000 years ago, Homo sapiens migrated out of Africa into what would become the fertile crescent.

The fertile crescent, as a “bridge” between Africa and Eurasia, had an unusually high amount of biodiversity. The eight “founder crops,” including wild ancestors to modern flax, wheat, barley, and lentils, grew here. The ancestor species of four out of the five modern domesticated livestock animals were native to here.

The presence of two major river systems also stimulated the invention of irrigation. This period is known as the Agricultural Revolution and marked the first point where humans moved from a nomadic lifestyle to settling in towns and villages. Instead of hunting and gathering, humans began growing and raising their own food supply.

Agriculture gave humans a greater degree of control over their food supply. As a result, the population began to grow.

The Middle Ages The human population grew at a steady rate, reaching about 800 million by 1800 A.D. Some density-dependent limiting factors were still in place. Famines Western Europe, 400-800 A.D. Mayan Civilization, 800-1000 A.D. Little Ice Age, 17th century Great Potato Famine (Ireland), 1845-1847 Disease Malaria (10,000 B.C.-present), cause of about half of all human deaths Black Plague (14th century), Eliminated 1/3 of Europe’s population.

The Industrial Revolution The industrial revolution began a multitude of new technologies and innovations. Electricity The steam engine Water treatment Antibiotics Vaccines The overall impact was a massive drop in infant mortality – the death rate in newborns. This led to an increase in overall average life expectancy. Pre-industrial life expectancy in Britain was 25-40 years. Current life expectancy worldwide is 67 years.

World Population “Dots” Video. Population Connection, 2003.

Industrialized farming, water treatment, and modern medicine removed many density- dependent limiting factors. The human population began to grow exponentially.

Industrial revolution Planet Earth: Population 7.3 Billion 2011 (7 billion) Billions of people 1999 (6 billion) 1987 (5 billion) 1974 (4 billion) 1960 (3 billion) Figure 6.1 The human population has grown exponentially—showing slow growth throughout most of history and shooting up at a rapid rate within the last 200 years. This graph also shows projections to 2100 that range from 8 billion to 16 billion. (This figure is not to scale.) 1930 (2 billion) 1800 (1 billion) Time Hunting and gathering Agricultural revolution Industrial revolution Fig. 6-1, p. 122

Exponential Growth Exponential growth occurs when the population size and its rate of growth both increase. It took over 70,000 years to reach 1 billion. 150 years to reach 3 billion. 25 years to reach 4 billion. 20 years to reach 5 billion 12 years to reach 6 billion. 11 years to reach 7 billion.

Doubling time is calculated with this equation: Another way of measuring growth is through doubling time, an estimate of how long it will take the population to double in size at its current rate of growth. Doubling time is calculated with this equation: 70 / (Current % Growth Rate) Year Growth Rate Doubling Time 1970 2.09 34 years 1980 1.82 38 years 1990 1.60 44 years 2000 1.26 56 years 2010 1.12 63 years

HUMAN DEMOGRAPHY Demographics is the study of human populations. Includes comparing statistics such as births, deaths, gender, race, and economic status. Developing countries have populations that tend to be poorer, younger, and are growing much more rapidly. Developed countries are wealthy, old, and tend to have decreasing population sizes.

The Human Population Can Grow, Decline, or Remain Fairly Stable Population change = (births + immigration) – (deaths + emigration) Crude birth rate The number of live births/1000/year Crude death rate The number of deaths/1000/year

NATURAL CAPITAL DEGRADATION Altering Nature to Meet Our Needs Reduction of biodiversity Increasing use of the earth's net primary productivity Increasing genetic resistance of pest species and disease-causing bacteria Elimination of many natural predators Introduction of potentially harmful species into communities Figure 6.A Major ways in which humans have altered the rest of nature to meet our growing population’s resource needs and wants. See an animation based on this figure at CengageNOW. Questions: Which three of these items do you believe have been the most harmful? Explain. How does your lifestyle contribute directly or indirectly to each of these three items? Using some renewable resources faster than they can be replenished Interfering with the earth's chemical cycling and energy flow processes Relying mostly on polluting and climate-changing fossil fuels Fig. 6-A, p. 124

Global Connections: The World’s 10 Most Populous Countries in 2008

Developing countries contain 80% of the world’s population, and will account for 90% of its projected growth.

Population (billions) 12 11 High10.8 10 Medium 9.3 9 8 7 Population (billions) Low7.8 6 5 Figure 6.2 Global connections: UN world population projections, assuming that by 2050 women will have an average of 2.5 children (high), 2.0 children (medium), or 1.5 children (low). The most likely projection is the medium one—9.3 billion by 2050. (Data from United Nations). 4 3 2 1950 1960 1970 1980 1990 2000 2010 2020 2030 2040 2050 Year Fig. 6-2, p. 125

Comparing developed and developing countries requires the use of these demographic variables: Life expectancy, or how long an average newborn will live in a society. Most affected by infant mortality rate. The total fertility rate, the average number of children a woman will have in her lifetime. A fertility rate above replacement level, 2.1, will generally result in a growing population. Below replacement level results in a shrinking population. Gross domestic product per capita is a measurement of standard of living. Total value of all goods and services produced in a country per person.

Country GDP Per Capita Total Fertility Rate Life Expectancy United States $49,965 1.89 78.6 Afghanistan $620 6.16 48.7 Afghan market. Photo by Staff Sgt. Russell Lee Klika

Life expectancy (and infant mortality) are highly correlated with GDP, up to about $4000/year.

TFR Rates for the U.S. between 1917 and 2008

Married women working outside the home 8% 81% 77 years Life expectancy 47 years 1900 2000 Married women working outside the home 8% 81% High school graduates 15% 83% Homes with flush toilets 10% 98% Homes with electricity 2% 99% Living in suburbs 10% 52% Figure 6-7 Some major changes took place in the United States between 1900 and 2000. Question: Which two of these changes do you think had the biggest impacts on the U.S. ecological footprint? Hourly manufacturing job wage (adjusted for inflation) $3 $15 Homicides per 100,000 people 1.2 5.8 Stepped Art Fig. 6-7, p. 132

Migration The movement of individuals between areas can have a major impact on population change. Emigration is when people move out of an area. More likely to occur in developing countries. Immigration is when people move into an area. More likely to occur in developed countries.

Japan had a fertility rate of 1.39 in 2011. In some developed countries, immigration offsets or delays the normal population decline. The United States total fertility rate in 2011 was 1.89, below replacement level. The overall immigration was over 11 million. The population growth rate was 0.7%. Japan had a fertility rate of 1.39 in 2011. The overall immigration was just over 200,000. Their population growth rate is -0.2%.

Several Factors Affect Birth Rates and Fertility Rates Children as part of the labor force Cost of raising and educating children Availability of private and public pension Urbanization Educational and employment opportunities for women Average age of a woman at marriage Infant mortality rates Availability of legal abortions Availability of reliable birth control methods Religious beliefs, traditions, and cultural norms

Several Factors Affect Death Rates Life expectancy - the average # of years an infant can expect to live Infant mortality rate: The infant mortality rate (IMR) is the number of deaths of infants under one year old, per 1,000 live births. High infant mortality rate indicates: Inadequate health care for poor women during pregnancy and their infants (poverty) Drug addiction among pregnant women High birth rate among teenagers

Several Factors Affect Death Rates (cont’d.) Less-developed countries (deaths per 1,000 live births) Infant mortality rate World Figure 6-10: Infant mortality rates for the world’s more-developed countries and less-developed countries, 1950–2012, with projections to 2050 based on medium population projections. More-developed countries Year Fig. 6-10, p. 129

In developed countries (like U.S.) Why are people living longer and fewer infants dying? Increased food supply and distribution Better nutrition (less malnutrition and undernutrition) Medical advances Improved sanitation

Population Pyramids When studying the demographics of a single country, two of the most important factors to examine are gender and age distribution. These variables are graphed as population pyramids, and can provide valuable insight into a country.

What is the overall shape of the graph? Is there a dominant age group or groups? What proportion of the 0-4 age group survives into the elderly (60+) age groups? Are the male and female sides roughly equal?

Generalized Population Age Structure Diagrams

Demographic Transition The fertility rate and population growth patterns in a given country will not remain constant. They change based on a wide variety of factors. United States Fertility Rates, 1911-2011

Population Growth : Opposing Factors Pronatalist pressures increase the likeliness of individuals within a population to have more children. Source of pleasure, pride, comfort. Source of support for elderly parents. Aid in supporting family income. Counteracting high child mortality rates. Social status – importance of having a son. Most antinatalist pressures involve women. Higher education and personal freedom. More opportunities to earn a salary. Higher socioeconomic status.

Demographic Transition Model Countries will typically pass through a series of stages as they industrialize and transition from developing to developed countries. During the pre-industrial stage, food shortages, malnutrition, poor sanitation, and lack of access to modern medicine keep death rates high. All regions of the world were in this stage up until the industrial revolution.

Population size begins to increase exponentially. During the early transition stage, access to food and medicine improves, leading to a rapid drop in death rates. Birth rates remain high, as family size is tied to cultural norms and religious beliefs. Population size begins to increase exponentially.

The population continues to increase, but more slowly. During the late transition stage, efforts are made to reduce birth rate. Birth control and sex education gain greater acceptance. Women play a greater role in family planning. The population continues to increase, but more slowly.

The population stabilizes. During the industrial stage, birth rates have fallen back into balance with death rates. Total fertility rate is close to replacement level. The population stabilizes.

The population size decreases. During the post-industrial stage, birth rates continue to fall due to antinatalist pressures Total fertility rate is below replacement level. The population size decreases.

Demographic Transition

Four Stages of the Demographic Transition

Some Problems with Rapid Population Decline Can threaten economic growth Labor shortages Less government revenues with fewer workers Less entrepreneurship and new business formation Less likelihood for new technology development Figure 6.11 Some problems with rapid population decline. Question: Which three of these problems do you think are the most important? Increasing public deficits to fund higher pension and health-care costs Pensions may be cut and retirement age increased Fig. 6-11, p. 133

FUTURE OF HUMAN POPULATIONS Most demographers believe the world population will stabilize sometime during the next century. Projections of maximum population size: Low 8 billion Medium 9.3 billion High 13 billion