HUMAN POPULATIONS

HUMAN POPULATIONS• Every second, on average, 4-5 children are born

somewhere on earth. In that same second, 2 other people die. This difference between births and deaths means a net gain of nearly 2.5 people per second in the world’s population.

– 9000 people per hour– 214,000 people per day– Over 6 million per month– 78 million per year

– If each one stood up, pronounced their name and sat down, it would take 600 years to complete roll call

– By 2025 it will take 1,000 years to complete this exercise

HUMAN POPULATIONS

World Population Clock

Population Ranks

U.S. POP Clock Projection

HUMAN POPULATIONS

7.2 ish Billion People2013

World Population Over the Centuries

9,000 human beings added to the planet every hour

World’s Human Population

• The human population hit 1 million about 15,000 years ago.

• The human population hit 1 billion in 1804.– 3 billion in 1960 ( 150 years to add 2 billion)– 1 billion people add between 1987-1999

• This means our population will double in about 40 years.

What is Exponential Growth?

• Which would you choose?

2 million dollars or

1 penny on day one and then double it each

day for 30 days.

Exponential Grwoth

0

1000000

2000000

3000000

4000000

5000000

6000000

1 3 5 7 9 11 13 15 17 19 21 23 25 27 29

Days

Money Series1

Series2

$5,368,709.12

0.01 1

0.02 2

0.04 3

0.08 4

0.16 5

0.32 6

0.64 7

1.28 8

2.56 9

5.12 10

10.24 11

20.48 12

40.96 13

81.92 14

163.84 15

327.68 16

655.36 17

1310.72 18

2621.44 19

5242.88 20

10485.76 21

20971.52 22

41943.04 23

83886.08 24

167772.16 25

335544.32 26

671088.64 27

1342177.28 28

2684354.56 29

5368709.12 30

Exponential Growth

• Exponential growth is marked by doubling. A few doublings can lead quickly to enormous numbers.

• It is deceptive because it starts out slowly, but rapidly gets out of hand.

Exponential Grwoth

0

1000000

2000000

3000000

4000000

5000000

6000000

1 3 5 7 9 11 13 15 17 19 21 23 25 27 29

Days

Money Series1

Series2

Reasons for the Human Population Explosion

• Causes of disease recognized• Improvements in nutrition• Discovery of antibiotics• Improvements in medicine• Increase in number of women who actually

reach child-bearing age• Short doubling times in some countries• Increased food production• Sanitation

What influences Growth rate?

What influences Growth rate?• Crude birth rate – the number of

births per thousand people.

• Crude death rate – the number of deaths per thousand people.

– If they are equal, there is zero population growth.

– If births is higher than deaths, then the pop. Goes up.

– Life expectancy – The average number of years someone is expected to live.

Calculating Fertility Rates and Doubling Times(CBR - CDR)/1000 x 100 =

% Rate of Increase or decrease in population per 1000 per year

70/ Rate of Increase = Doubling Time

Doubling time- The time it takes for the population to double the number of people

Growth Rate- includes birth rate, death rate, immigration and emigration

Factors Affecting Death Rates• Death rates have declined because of:

– Increased food supplies, better nutrition.– Advances in medicine.– Improved sanitation and personal hygiene.– Safer water supplies.

• U.S. infant mortality is higher than it could be (ranked 46th world-wide) due to:– Inadequate pre- and post-natal care for poor.– Drug addiction.– High teenage birth rate.

Infant mortality rate- Number of child/infant deaths.

If a mother lives in an area with a high infant mortality rate she will tend to have a lot of children to ensure some will make it to adulthood.

Zero Population Growth- When the number of births, equals the number of deaths. No growth in the population.

Total Fertility Rate- an estimate of the average number of children a women will have during her childbearing years.

Factors that affect birth & fertility rates

• Importance of kids in labor force

• Urbanization• Cost of raising &

educating kids• Availability of private

& public pensions• Religious beliefs,

traditions & cultural norms

• Educational & employment opportunities

• Infant mortality rate• Average age at

marriage• Availability of reliable

birth control

Replacement-level fertility- the number of children a couple must bear to replace themselves. It is slightly higher than two children per couple. (2.2 in developed countries and as high as 4.5 in some developing countries)

It is greater in countries w/ high infant mortality rates than in countries w/ low infant mortality rates

Factors Affecting Birth Rates and Fertility Rates

• The number of children women have is affected by:– The cost of raising and educating them.– Availability of pensions.– Urbanization.– Education and employment opportunities.– Infant deaths.– Marriage age.– Availability of contraception and abortion.

Fig. 9-3, p. 174

Average crude death rate

Average crude birth rate

World21

9

All developedcountries

11

10

All developingcountries

27

8

9

23

Developingcountries

(w/o China)

Other factors that influence a countries population

• Immigration – the migration or movement of people into a country or area to take up permanent residence.

• Emigration – the migration or movement of people out of a country.

• Net Migration- Total number of people moving into or out of the population.

Reasons to Immigrate

1. Work2. Money3. Political Safety4. Freedom of Religion5. To Escape War 6. Famine7. For a Better Education8. Different Government9. Tolerance

• Usually people immigrate to start a better life for them or their families. Some come alone in hope that they can soon bring the rest of their family. Others work so they can send money to help those where they came from.

Case Study: U.S. Immigration

• Since 1820, the U.S. has admitted almost twice as many immigrants and refugees as all other countries combined.

Figure 9-8Figure 9-8

FACTORS AFFECTING HUMAN POPULATION SIZE

• Population increases because of births and immigration and decreases through deaths and emigration.

• Instead of using raw numbers, crude birth rates and crude death rates are used (based on total number of births or deaths per 1,000 people in a population).

Demographics

• Demography – Keeps track of human populations. The data collected is used to show age structures (number of people in various age brackets), and is separated by gender (male and female). Population profiles (graphs) are used to determine age structures (proportions of people in each age bracket), and are used to make predictions of future population trends.

Demographics

• A demographer studies vital statistics about people, such as birth rates, death rates, where they live, as well as population size.

• They compare country to country, state to state, region to region.

• They can predict trends that can be important to plan the future.

Demographics

• They study the populations of developed countries and non-developed countries.– Developed countries are those that are

industrialized and/or have high standards of living.

– Less-developed countries are those that have very little industrialization and/or low standards of living.

Demographics

• Developed– High literacy rates– High standards of living– Low birth rate– Low death rate– Slow or Zero population

growth– High life expectancy– Rich– High per capita– High Energy Consumption– Urban populations

• Less-Developed– Low literacy rates– Low standard of living– High birth rate– High death rate– Rapid population growth– Low life expectancy– Poor– Widespread Disease– Low per capita– Rural populations

Economic Categories Based on Per Capita Gross National Income

• Gross National Product (GNP)- The most commonly used measure of the economic growth of a country.

per capita – takes into relation countries population

• High-income, highly developed, industrialized countries– United States, Japan, Canada– Average GNI per capita = $26,710

• Middle-income, moderately developed countries– Latin America, South Africa, China– Average GNI per capita = $1,850

Economic Categories Based on Per Capita Gross National Income

• Low-income, developing countries– Western and central Africa, India, central Asia– Average GNI per capita = $430

Major Economic Divisions of the World

Gross national income/capita

The Poverty Cycle

Disparities

• Developed countries– 15% of the world’s population– Control 80% of the world’s wealth

• Low-income developing countries– 37% of the world’s population– Control 3.0% of the world’s gross national

income

• Difference in per capita income: 63 to 1!

Dimensions of the Human Poverty Index

Stabilizing Population and Eradicating Poverty

• Universal primary education• Eradication of adult illiteracy• School lunch programs for 44 poorest countries• Assistance to preschool children and pregnant

women in 44 poorest countries• Reproductive health care and family planning

services

Total Additional Annual Cost = $77 billion

Photo Credit: iStockPhoto / Wallenrock

Poor (less developed) countries have high population growth rates therefore, high populations.

More developed (richer) countries have little or no population growth.

Histograms• These population histograms show the

age distribution and help predict the age dist. for the future.

10 years later

• The age structure histogram below shows the percentage of population for both male (left) and female (right) for three nations, Mexico (rapid growth), U.S. (slow growth) and Sweden (zero growth). The shaded areas on each graph show people in their child bearing years.

What is the growth rate?

Age structure- Percentage of the population at each age

level in a population

Generation time- the time it takes for 1 generation to pass.

POPULATION AGE STRUCTURE

• The number of people in young, middle, and older age groups determines how fast populations grow or decline.

• The number of people younger than age 15 is the major factor determining a country’s population growth.

• Changes in the distribution of a country’s age groups have long-lasting economic and social impacts.

POPULATION AGE STRUCTURE

• Populations with a large proportion of its people in the preproductive ages 1-14 have a large potential for rapid population growth.

Figure 9-9Figure 9-9

Population Profile of Italy

U.S. Statistics

• Because of the ‘Baby Boom’ the US has a bulge in the pyramid with people in their 50’s-60’s.

• There are also more women than men in the older age group because of differences in longevity between the sexes.

(Cont…)

POPULATION AGE STRUCTURE

• Today, baby boomers make up nearly half of all adult Americans and dominate the populations demand for goods and services.

Figure 9-11Figure 9-11

POPULATION AGE STRUCTURE

• About 14% of the world’s population live in countries with stabilizing or declining populations.

• Rapid population decline can lead to long-lasting economic and social problems.

• Death from AIDS can disrupt a country’s social and economic structure by removing significant numbers of young adults.

• Global again may help promote peace.

POPULATION AGE STRUCTURE

• Some problems with rapid population decline.

• Which of these problems do you believe are the most important?

Figure 9-13Figure 9-13

Population Profile United States

Population Profile United States

Population Profile United States•US Population Growth Histogram

SOLUTIONS: INFLUENCING POPULATION SIZE

• Demographic Transition: As countries become economically developed, their birth and death rates tend to decline.– Preindustrial stage: little population growth

due to high infant mortality.– Transitional stage: industrialization begins,

death rates drops and birth rates remain high.– Industrial stage: birth rate drops and

approaches death rate.

SOLUTIONS: INFLUENCING POPULATION SIZE

• Generalized model of demographic transition.– Some developing countries may have difficulty making

the demographic transition.

Figure 9-14Figure 9-14

Population Density

Population Density

http://www.epa.gov/maia/index-txt.html

World Population Over the Centuries

9,000 human beings added to the planet every hour

Do you think our world can handle this many people?

• Carrying capacity – The maximum number of individual species that can be supported by an ecosystem on a long term basis.

Carrying Capacity

• At this point, the environment can no longer provide for the species, due to a number of different environmental resistances, including food, crowding, competition, etc. The population, due to lack of resources, will begin to die out, allowing the environment to recover. As the environment recovers, the species population is able to flourish once more. This leads to a fluctuation between the prosperity of the species and the prosperity of the environment (hence the fluctuations in the graph). 

Biotic potential – if resources were unlimited, optimal conditions.

Human predictions

• If there was a continued growth and not death, food would run short and available space would run out.

• But, humans can’t reproduce as fast as other animals.

• This helps to stop the growth.

Effects of Overpopulation?

• Food Shortage - famine

• Natural recourses shortage

• Land Overuse• War• Disease• Pollution-waste

managment

Consequences of Exploding Populations

More PopulationCauses

MORE

LESS

deforestationresource depletionloss of agricultural landbiodiversitydiseasepest resistancepopulation migrationirrigationwetlands

Reasons for World Hunger Issues

• Unequal distribution of available food

• Loss of arable land

• Increasing population growth rate

• Increasing poverty in developing countries

Strategies for ensuring adequate nutrition for a growing population:

• Increase the number of new food crops from a diversity of plant species

• Distribute food more equitably• Increase land are that is dedicated to grain

production rather than meat production• Assist developing countries in efficient

crop irrigation systems.

HUMAN ASPECTS ON NATURAL SYSTEMS

• We have used technology to alter much of the rest of nature in ways that threaten the survival of many other species and could reduce the quality of life for our own species.

Figure 9-17Figure 9-17

Developed Countries

• High rates of resource use• Result in high levels of pollution and

environmental degradation per person

• These are believed to be the key factors determining overall environmental impact.

(Cont….)

It is estimated that a US citizen consumes 35 X’s as much as the average citizen of India and 100 X’s as much as the average person in the world’s poorest countries.(Cont…)

Thus, poor parents in a developing country would need 70-200 kids to have the same lifetime environmental impact as 2 typical US kids.

Urban areas must import most of its food, water, energy, minerals, & other resources.

They produce enormous quantities of wastes that can pollute the air, water & land.

44% of the world’s people live in urban areas that occupy only 5% of the world’s land & they consume 75% of the world’s resources.

Core Case Study: Is the World Overpopulated?

• The world’s population is projected to increase from 6.6 billion to 8.9 billion between 2006 and 2050.

• The debate over interactions among population growth, economic growth, politics, and moral beliefs is one of the most important and controversial issues in environmental science.

Core Case Study: Is the World Overpopulated?

• Some argue that the planet has too many people.

• Some feel that the world can support billions of more people due to technological advances.

• There is a constant debate over the need to reduce population growth.– Must consider moral, religious, and personal

freedom.

Population Control

• Psychological/Behavioral: abstention, calendar rhythm method

• Mechanical: condoms, diaphragms

• Chemical: the pill, Norplant

• Surgical: tubal ligation, vasectomy

• Intrauterine Devices (IUD): abortion device

• An important example of mandated population control is China's one-child policy, in which having more than one child is made extremely unattractive. This has led to allegations that practices like infanticide, forced abortions, and forced sterilization are used as a result of the policy.

China’s Family Planning Program

• Currently, China’s TFR is 1.6 children per women.

• China has moved 300 million people out of poverty.

• Problems:– Strong male preference leads to gender

imbalance.– Average population age is increasing.– Not enough resource to support population.

Some countries, including China, penalize couples who have more than one or two children by:

1. Raising their taxes

2. Charging other fees

3. Eliminating income tax deductions for a couple’s third child

4. Loss of health-care benefits, food allotments and job options

In China couples who pledge to have no more than one child receive

1. Extra food

2. Larger pensions

3. Better housing

4. Free medical care

5. Salary bonuses

6. Free school tuition for their one child

7. Preferential treatment in employment when their child enters the job market.

India’s Failed Family Planning Program

• Poor planning.• Bureaucratic inefficiency.• Low status of women.• Extreme poverty.• Lack of administrative financial support.• Disagreement over the best ways to

slow population growth.

Putting It All Together: Social Modernization

% Increase= (Final Total – Initial Total)/ Initial total x 100

70/ Rate of Increase = Doubling Time

(CBR - CDR)/1000 x 100 = % Rate of Increase or decrease in population per 1000 per year

CB(D)R per 1000 = (# Births / Total Population) x 1000

Chapter 18

Environmental Hazards and Human Health

RISKS AND HAZARDS

• Risk is a measure of the likelihood that you will suffer harm from a hazard.

• We can suffer from:– Biological hazards: from more than 1,400

pathogens.– Chemical hazards: in air, water, soil, and food.– Physical hazards: such as fire, earthquake,

volcanic eruption…– Cultural hazards: such as smoking, poor diet,

unsafe sex, drugs, unsafe working conditions, and poverty.

Transmissible Disease

• Pathway for infectious disease in humans.Figure 18-4Figure 18-4

Transmissible Disease

• WHO estimates that each year the world’s seven deadliest infections kill 13.6 million people – most of them the poor in developing countries.

Figure 18-5Figure 18-5

Case Study: Malaria – Death by Mosquito

• Malaria kills about 2 million people per year and has probably killed more than all of the wars ever fought.

Figure 18-7Figure 18-7

Case Study: Malaria – Death by Mosquito

• Economists estimate that spending $2-3 billion on malaria treatment may save more than 1 million lives per year.

• Window screens, predatory fish, vitamins, and pesticides.

Figure 18-6Figure 18-6

CHEMICAL HAZARDS

• A toxic chemical can cause temporary or permanent harm or death.– Mutagens are chemicals or forms of radiation

that cause or increase the frequency of mutations in DNA.

– Teratogens are chemicals that cause harm or birth defects to a fetus or embryo.

– Carcinogens are chemicals or types of radiation that can cause or promote cancer.

LD50 – Lethal dose 50%

• A helpful measurement for comparing the harmful effects of different chemicals.

• By quantifying the LD50 value for a new chemical, scientist can compare the value to thousands of previous tests.

• They can determine whether a new chemical is more or less lethal in comparison to other chemicals that are being used.

Effects of Chemicals on the Immune, Nervous, and Endocrine

Systems• Long-term exposure to some chemicals at low

doses may disrupt the body’s:– Immune system: specialized cells and tissues

that protect the body against disease and harmful substances.

– Nervous system: brain, spinal cord, and peripheral nerves.

– Endocrine system: complex network of glands that release minute amounts of hormones into the bloodstream.

Effects of Chemicals on the Immune, Nervous, and Endocrine

Systems

• Molecules of certain synthetic chemicals have shapes similar to those of natural hormones and can adversely affect the endocrine system.

Figure 18-9Figure 18-9

Case Study: A Black Day in Bhopal, India

• The world’s worst industrial accident occurred in 1984 at a pesticide plant in Bhopal, India.– An explosion at Union Carbide pesticide plant in

an underground storage tank released a large quantity of highly toxic methyl isocyanate (MIC) gas.

– 15,000-22,000 people died– Indian officials claim that simple upgrades could

have prevented the tragedy.

TOXICOLOGY: ASSESSING CHEMICAL HAZARDS

• Factors determining the harm caused by exposure to a chemical include:– The amount of exposure (dose). – The frequency of exposure.– The person who is exposed.– The effectiveness of the body’s detoxification

systems.– One’s genetic makeup.– Current health status

TOXICOLOGY: ASSESSING CHEMICAL HAZARDS

• Estimating human exposure to chemicals and their effects is very difficult because of the many and often poorly understood variables involved.

Figure 18-11Figure 18-11

TOXICOLOGY: ASSESSING CHEMICAL HAZARDS

• Children are more susceptible to the effects of toxic substances because:– Children breathe more air, drink more water, and

eat more food per unit of body weight than adults.– They are exposed to toxins when they put their

fingers or other objects in their mouths.– Children usually have less well-developed immune

systems and detoxification processes than adults.