The human population and the environment Chapter 7 AP Environmental The human population and the environment Chapter 7

History of Human Population Growth The human population increased slowly until the last 200 years Initially the human population was limited by resources provided by the land and higher mortality rates for a younger age demographic

History of Human Population Growth Hunters and gatherers The world’s population was probably less than a few million Early, pre-industrial agriculture Allowed a much greater density of people The first major increase in human population Machine age Industrial revolution led to rapid increase in human population The Modern era Rate of population has slowed in wealthy nations but continues to increase rapidly in poorer, less developed nations.

Current Human Population Growth Technology, medical advancements, better sanitation and food distribution have all contributed to the current exponential growth of the human population Estimates state that every second 4 children are born and one person dies Overpopulation trends have been identified as the biggest contributing factor in resource depletion and environmental degradation

Population Changes Exponential growth represents a constant net rate of increase. The rate of net increase for the human population in the graph has exceeded the exponential rate Factors like a decline in death rate have caused the growth in the net rate of increase

Exponential growth and doubling time The current growth rate for the human population falls between 1-2% so doubling time is expected to be between 35-70 years. *Remember: doubling time = 70/R No population can sustain exponential growth rate indefinitely because of resource constraints within the environment so some scientists believe that the human population will start to level out around 11 billion people by year 2100

How do we measure the human population? A group of individuals of the same species living in the same area of interbreeding and sharing genetic information. Species: All individuals that are capable of interbreeding. Made up of populations Population dynamics The general study of population changes.

Population Dynamics Formula to represent population change: Human population is usually presented as a crude rate which is a given number per 1000. Example: If the crude death rate is 9 then that represents 9 out of every 1000 people died in that given time frame. Expressed as a percentage this would equal 0.9%. Crude growth = crude birth rate – crude death rate ( g = b-d) and represents a net change in the population P1 = number of individuals at a given time P2 = number of individuals at a later time P2 = P1 + (B – D) + (I – E)

Population Dynamics Growth rates can be determined using a series of equations that factor in the number of births or deaths in a population with a known population size (N). birth rate (b)= B/N death rate (d) = D/N Growth rate (g) = (B-D)/N

Perspectives on Population Growth Given the current population of the Earth, what factors influence population growth rates in the future and how the size of the human population will impact the environment?

Perspectives on Population Growth Thomas Malthus (1798 An Essay on the Principle of Population) Argues that population growth is tied to food resources so when the population gets too large the lack of food resources will cause the population to decline Depletion of resources will lead to poverty, war, starvation, etc.

Perspectives on Population Growth Karl Marx (1818-1883) Argued that poor economic and social conditions (oppression of workers, exploitation of resources) led to poverty which in turn led to higher birth rates and more resource depletion With increasing environmental degradation and resource depletion overpopulation would lead to unequal distribution of resources, starvation, war, etc.

Perspectives on Population Growth The opposing viewpoints of Malthus and Marx beg the question: Is it more important to focus on reducing population size or reducing poverty to prevent further environmental degradation?

China Case Study 1960’s : uncontrolled population growth was leading to food resource issues and the possibility of mass starvation in some provinces 1970’s: government begins to focus on slowing population growth 1979: Implementation of “One Child Policy” Encouraged young professionals to focus on career before family Government offered free contraceptives, sterilization and abortion Families that agreed to one child given increased pension, better housing, free food, salary bonuses, free medical care and free school (all taken away if families later exceeded one child) 2001: Studies showed fertility rates dropped from 6.5 to 1.3 children per woman 2015: Phase out of “One Child Policy”

Population Solutions Delay the age of first childbearing by women Birth control Biological and Social Breast-feeding, which can delay resumption of ovulation Abstinence Induction of sterility with natural agents Contraceptive devices National Programs to Reduce Birth Rates Formal family planning programs to explain the problems arising from rapid population growth Describe the benefits to individuals of reduced population growth. Education Jobs for women Family planning flyer from Singapore

Where do you see population trends increasing? Why? Population Changes Where do you see population trends increasing? Why?

Population Changes

Growth Factors Total Fertility Rate (TFR) is a major factor in the growth or maintenance of a population over time. Total fertility refers to the average number of children that could be born to a woman if she follows the normal rates of fertility and survives from birth through her reproductive years. An important figure in fertility is called Replacement Level Fertility. Replacement level fertility means that a woman produces enough children to maintain the current population levels

Growth Factors Fertility rates are generally higher in developing countries because of a need for labor and caregivers within the household, a lack of education in birth control, and cultural beliefs Worldwide fertility rates are dropping due to higher levels of urbanization, especially in developing countries (Current TFR = 2.6) If fertility rates were to drop below replacement levels then the population could stabilize by 2100

Population Outlook

Age Structure Graphs Population age structure: The proportion of the population in each age class, also divided by gender Shows possible effects on current and future birth rates, death rates and growth rates Can be used as a predictor for future impacts on the environment Can predict complications for current and future social and economic status in a country.

Age Structure

Population Growth Factors Mortality rates are dependent upon access to clean water, good hygiene, sanitary living conditions and access to medical care Declining mortality, not increases in fertility contribute to current population growth World mortality rates do not currently offset natality rates leading to natural increases in most populations The current growth rate of the world is 1.08% meaning the population will double in approximately 65 years

Population Growth Factors Life expectancy is the average age a newborn infant is expected to attain For most of human history average life expectancy was 30 years Increased medical care, sanitation, etc. have increased the average life expectancy to 71.2 Life Expectancy By Country (2017 data from CIA Factbook) Top 5 Bottom 5 Monaco 89.4 Swaziland 52.1 Japan 85.3 Gabon 52.1 Singapore 85.2 Afghanistan 51.7 Macau 84.6 Guinea-Bissau 51 Iceland 83.1 Chad 50.6

Population Growth Factors Life Expectancy Patterns: Women generally have higher life expectancies than men Life expectancy tends to increase with annual income Worldwide life expectancy has been steadily increasing in the last 30 years

Demographic Implications As populations stabilize and reduce the number of children born into a country the ratio of people in the young working class begins to drop below the numbers of those in the older age groups that are retired and are dependent upon government support Higher numbers of older, non-working individuals puts a stress on the economy of a country Sudden increases such as the “baby-boomer” population in the United States can also cause temporary stresses

Birth Dearth In developed countries fertility rates have started to drop below the standard fertility rate of 2.1 children per woman needed to maintain a population (Italy 1.5, Japan, 1.3) Declining populations in these countries will no longer be able to fill the jobs needed to support the economy or provide soldiers to bolster military strength By 2030 the former world superpower countries in Europe and North America may only account for 9% of the total world population

Immigration/Emigration Movement of people between countries has become necessary for economic stability of countries experiencing fertility declines The United States averages 800,000 immigrants each year entering the population while European numbers have seen numbers in the millions due to the recent refugee crisis 2016 estimates for number of refugees was 60 million

How did we get here? Much of the current population growth today can be attributed to the economic development that occurred during the industrial revolution Economic development leads to increased jobs, better medicine and improved living conditions for a population Modernization of a population affects birth and death rates over time in a demographic transition

Demographic Transition Three-stage pattern of change in birth rates and death rates. Occurred during the process of industrial and economic development of Western nations. Leads to a decline in population growth. Stage I: Decline in death rate Stage II: High growth rate Stage III: Birth rate drops toward the death rate, leading to low or zero growth rate

Demographic Transition

Demographic Transition

Demographic Transition Benefits Population stabilization Increased technology availability Growing prosperity and social reform Concerns Countries that get “trapped” in the middle transitional stage Social justice