The Human Population. Human Population Over Time After growing slowly for thousands of years, the...

The Human PopulationThe Human Population

Human Population Over TimeHuman Population Over Time

After growing slowly for thousands of years, After growing slowly for thousands of years, the human population grew rapidly in the the human population grew rapidly in the 1800s.1800s.

The History of Human Population GrowthThe History of Human Population Growth

Years HumanElapsed Year Population

3,000,000 10,000 B.C. (Agricultural Revolution) 5-10 Million 10,000 1 A.D. 170 Million 1,800 1800 (Industrial Revolution) 1 Billion 130 1930 2 Billion 30 1960 3 Billion 15 1975 4 Billion 12 1987 5 Billion 12 1999 6 Billion 8 2008 6.7 Billion


Why was the population able to grow so Why was the population able to grow so rapidly during this period of time?rapidly during this period of time? Increases in food productionIncreases in food production Improvements in hygiene that came with industrial Improvements in hygiene that came with industrial

and scientific improvementsand scientific improvements

Enabling GrowthEnabling GrowthAgriculture:

About 12,000 years ago, several cultures shifted from hunting and gathering to farming.

Humans became the first and only species ever to control our own food supply, and steady population growth was the result.

In the absence of other limiting factors, any population will expand to the limit of its food supply; this happens so reliably that it is considered a law of ecology.

Agricultural ImprovementsAgricultural Improvements

Enabling GrowthEnabling GrowthTechnology:

The development of agriculture led by turns to settlement, division of labor, mathematics, literacy, and science.

By about 1800, major advances collectively referred to as the “Industrial Revolution” were occurring.

Breakthroughs in medicine, nutrition and sanitation brought down child mortality rates and led to longer life spans.

The mechanization of agriculture and improvements in food preservation led to even greater increases in food production and availability.

Human numbers began doubling at an unprecedented pace.

Rates of GrowthRates of Growth Past: A graph of human population

before the agricultural revolution would likely have suggested a wave, reflecting growth in times of plenty and decline in times of want, as graphs of other species‘ populations continue to look to this day.

The graph of recent human population growth is referred to as a "J curve," as it follows the shape of that letter, starting out low and skyrocketing straight up.

Rates of GrowthRates of GrowthPresent: World population reached 6 billion people in

1999, and it is over 6.6 billion in 2007. At the present rate of growth; over 77 million

a year, the world adds a New York City every month, a Germany every year and a Europe each decade.

Teen childbearing rates in the US are the highest in the developed world and 11% of all US births are to teenage mothers.

Rates of GrowthRates of Growth

The United States, with over 300 million people, is growing by more than 2.8 million people each year. At this rate, we are one of the fastest growing industrialized nations in the world, and we have the third largest population of all nations, preceded only by China and India.

Rates of GrowthRates of GrowthFuture: With a current annual growth rate of 1.2%,

world population is projected to double in just 58 years.

Our doubling times will be realized if and only if growth rates remain constant.

Today, the world's birth rate is about two and a half times its death rate. The closer these two rates are, the slower population growth will be.

Rates of GrowthRates of Growth

Zero population growth is the demographic term for the state of equilibrium reached when birth and death rates are the same.

Momentum is also a factor in population growth. Some countries, like the U.S., are growing even

though the average woman has just two children. In such cases, a population can still take 60-70 years

to stabilize, and will do so only when the percentage of elderly people is equal to the percentage at child-bearing age

Studying Human PopulationsStudying Human Populations

The human population of Earth grew faster in The human population of Earth grew faster in the 20the 20thth century than ever before. century than ever before.

Demography is the study of populations.Demography is the study of populations. Demographers study historical size and makeup of Demographers study historical size and makeup of

populations to make comparisons and predictions.populations to make comparisons and predictions.

Demography Cont.Demography Cont.

Demographers also study properties that affect Demographers also study properties that affect population growth.population growth. Ex: economics and social structureEx: economics and social structure

Countries are grouped into 2 different categories:Countries are grouped into 2 different categories: Developed countries: higher average incomes, slower Developed countries: higher average incomes, slower

population growth, diverse industrial economies, strong population growth, diverse industrial economies, strong social supportsocial support

Developing countries: lower average incomes, simple Developing countries: lower average incomes, simple agriculture-based economies, and rapid population growthagriculture-based economies, and rapid population growth

Forecasting Population SizeForecasting Population Size

Population Size is determined by:Population Size is determined by: Age structureAge structure SurvivorshipSurvivorship Fertility RatesFertility Rates MigrationMigration

Forecasting Population SizeForecasting Population Size

Age Structure: the distribution of ages in a Age Structure: the distribution of ages in a specific population at a certain time.specific population at a certain time. Countries that have a high rate of growth usually Countries that have a high rate of growth usually

have more young people than older people.have more young people than older people.

Countries that have a slow rate of growth or an Countries that have a slow rate of growth or an even rate of growth usually have an even age even rate of growth usually have an even age distribution. distribution.

Population PyramidPopulation Pyramid

Forecasting Population Size Cont.Forecasting Population Size Cont.

Survivorship: the percentage of members of a Survivorship: the percentage of members of a group that are likely to survive to any given group that are likely to survive to any given age.age. Demographers study a group of individuals that Demographers study a group of individuals that

were born at the same time and notes when each were born at the same time and notes when each group member dies.group member dies.

The results are plotted on survivorship curves.The results are plotted on survivorship curves.

Survivorship CurvesSurvivorship Curves

Type I Curves:Type I Curves: Most people live to old age Most people live to old age Type II CurvesType II Curves: Similar death rates at all ages: Similar death rates at all ages Type III Curves:Type III Curves: the pattern in very poor the pattern in very poor

human populations in which many children diehuman populations in which many children die

Type I and type III survivorship may result in Type I and type III survivorship may result in populations that remain the same size or grow populations that remain the same size or grow slowly.slowly.

Survivorship CurvesSurvivorship Curves


Fertility Rates:Fertility Rates: the number of babies born the number of babies born each year per 1,000 women in a populationeach year per 1,000 women in a population Replacement level:Replacement level: the average number of children the average number of children

each a parent must have in order to “replace” each a parent must have in order to “replace” themselves in a population.themselves in a population.

This number is 2.1 or slightly more than 2, because This number is 2.1 or slightly more than 2, because not all children born will survive.not all children born will survive.

In 1972, the total fertility rate dropped below the In 1972, the total fertility rate dropped below the replacement rate and remained there for most of replacement rate and remained there for most of the 1990s.the 1990s.

Total Fertility RateTotal Fertility Rate


Migration: the movement of individuals Migration: the movement of individuals between areasbetween areas Immigration: movement into an areaImmigration: movement into an area Emigration: movement out of an areaEmigration: movement out of an area

How Have Fertility Rates Changed How Have Fertility Rates Changed in the U.S.?in the U.S.?

Between 1910 and 1930, birth rates fell Between 1910 and 1930, birth rates fell sharply as sharply as the country underwent industrialization and the country underwent industrialization and

urbanizationurbanization More women got an education and began working More women got an education and began working

outside the homeoutside the home


In the 1930s, the birth rate remained low due to In the 1930s, the birth rate remained low due to the Great Depression and then began rising in the the Great Depression and then began rising in the 1940s during World War II.1940s during World War II.

The sharp rise in birth rates after World War II is The sharp rise in birth rates after World War II is known as the baby boom period when 79 million known as the baby boom period when 79 million people were added to the U.S. population.people were added to the U.S. population.

Between 1956 and 1972, the birth rate began to Between 1956 and 1972, the birth rate began to drop as more women began working outside of drop as more women began working outside of the home.the home.


Between 1977 and 2000, a small echo boom in Between 1977 and 2000, a small echo boom in the number of births per year occurred as large the number of births per year occurred as large numbers of people born during the baby boom numbers of people born during the baby boom began having children.began having children.

According to the U.S. Bureau of Census, the According to the U.S. Bureau of Census, the population of the U.S. will increase from 288 population of the U.S. will increase from 288 million to 414 million between 2002 and 2050 million to 414 million between 2002 and 2050 and will reach 571 million by 2100.and will reach 571 million by 2100.

Declining Death RatesDeclining Death Rates

The dramatic increase in Earth’s population in The dramatic increase in Earth’s population in the last 200 years has occurred because death the last 200 years has occurred because death rates have declined more rapidly than birth rates have declined more rapidly than birth rates.rates. Life Expectancy:Life Expectancy: the average number of years a the average number of years a

person is expected to liveperson is expected to live For people in many developed countries life expectancy For people in many developed countries life expectancy

is 80 yearsis 80 years

Life ExpectancyLife Expectancy

The Demographic TransitionThe Demographic Transition

Demographic transition:Demographic transition: the shift from high the shift from high birth rates to low birth rates during birth rates to low birth rates during industrializationindustrialization

This occurs in four stages.This occurs in four stages.

Stages of Demographic TransitionStages of Demographic Transition

11stst Stage preindustrial conditions: Stage preindustrial conditions: birth rate and birth rate and death rate are both high and population is stabledeath rate are both high and population is stable

22ndnd Stage population explosion: Stage population explosion: death rate decline as death rate decline as hygiene, nutrition and education improvehygiene, nutrition and education improve

33rdrd Stage Stage population growth slows as birth rate population growth slows as birth rate decreasesdecreases

44thth Stage Stage birth rate drops below replacement rate, so birth rate drops below replacement rate, so the population begins to decrease the population begins to decrease

The Demographic TransitionThe Demographic Transition

Changing Population TrendsChanging Population Trends

Some countries have reached the demographic transition- they have reached large population sizes and have increased life expectancies.

Throughout history, populations that have high rates of growth create environmental problems.

Rapidly growing populations use resources at an increased rate and tax infrastructure. Infrastructure: water supplies, sewer plants, power

companies, roads, subways, schools and hospitals

Problems of Rapid GrowthProblems of Rapid Growth

Shortage of Fuelwood:Shortage of Fuelwood: In many poor countries, wood is the main fuel In many poor countries, wood is the main fuel

source.source. When populations are stable, people are able to use When populations are stable, people are able to use

deadwood.deadwood. When populations grow rapidly, deadwood does When populations grow rapidly, deadwood does

not accumulate fast enough.not accumulate fast enough. This results in forests being cleared of vegetation.This results in forests being cleared of vegetation.


Unsafe Water: In some areas of the world, the local water supply

may be used not only for drinking water and washing but also for sewage disposal.

The water systems many cities cannot keep up the rapidly expanding populations.

In 2001, nearly 1 billion people lacked adequate drinking water and 3 million died from diseases that were spread through water.

Density vs. Consumption

Water Pollution: In the U.S., 40% of streams, 45% of lakes, and 50%

of estuaries are unfit for swimming or fishing. Agricultural chemicals, eroded sediment, and animal

wastes have fouled over 173,000 miles of waterways. Almost 45% of our drinking water comes from

groundwater sources, and 38 states reported finding pesticides, some carcinogens, in their groundwater.

Unsafe Drinking WaterUnsafe Drinking Water


Impacts on Land Growing populations have shortage of arable land

(land that is suitable for growing crops) Growing populations make tradeoffs between

using land for agriculture, housing, or natural habitats.

Much of the world is undergoing urbanization resulting in suburban sprawl.


Land Use: In the last 200 years the United States has lost

at least: 71% of its topsoil, 50% of its wetlands, 90% of its northwestern old-growth forests, and 99% of its tall grass prairie.

In the United States, more than 8,000 square miles of land per year disappear under suburban sprawl—most often land of superior quality for agriculture

Density vs. Consumption Degree of Impact: The impact of any human group on its environment has to do

with three equally important factors. The first is the number of people. The second factor encompasses the ways in which we

manufacture goods, design communities, and use technology. The third is the actual amount of resources consumed by each

person.

Unfortunately, the rate at which industrialized nations consume resources makes their populations' effect on the planet vastly greater than that of developing countries.


Energy: Americans constitute less than 5% of the

world's population, but are responsible for nearly 23% of the world's annual energy consumption, including 25% of fossil fuels.

On average, one American consumes as much energy as 2 Germans, 7 Syrians, 12 Columbians, 24 Indians, 100 Haitians, or 286 Ethiopians.

Global Energy ConsumptionGlobal Energy Consumption


Natural Resources: A person living in an industrialized country

consumes twice as much grain, three times as much meat, nine times as much paper and eleven times as much gasoline as someone in a developing country.

North America, with 5% of the world’s population, consumes 30% of the aluminum

Global Natural Resource UseGlobal Natural Resource Use

Density vs. Consumption Global Warming: In 2004, the U.S. was responsible for 22% of the

world’s carbon dioxide emissions, more than any other country.

China, with over four times more people than the U.S., produces less than 80% of the carbon dioxide that the U.S. produces, but their CO2 output has been growing steadily over the past decade.

Carbon dioxide is the primary greenhouse gas, responsible for 60% of global warming caused by greenhouse gases.

Global Carbon Dioxide ProductionGlobal Carbon Dioxide Production


Waste: The more we consume, the more waste we produce.

By the time a baby born today in the United States reaches the age of 82 years, he or she will have produced at least 60 tons of garbage.

The average American generates 4.4 lbs. of solid waste each day.

Average people in France produce 2.9 pounds and in South Africa 1.5 pounds, while residents of Egypt and Pakistan produce less than 1 pound per day.

Managing Development and Managing Development and Population GrowthPopulation Growth

Countries such as Thailand, China, and India Countries such as Thailand, China, and India have created campaigns to reduce fertility rates have created campaigns to reduce fertility rates in their citizens.in their citizens.

These campaigns include family planning These campaigns include family planning programs, public advertising, economic programs, public advertising, economic incentives, and legal punishments.incentives, and legal punishments.

WORLD POPULATION GROWTH — WORLD POPULATION GROWTH — SOLUTIONSSOLUTIONS

Making sure people around the world have access to Making sure people around the world have access to family planning services. family planning services.

Empowering women in developing countries Empowering women in developing countries economically, socially, and legally in a manner that economically, socially, and legally in a manner that results in them having an equal say (with their results in them having an equal say (with their husbands) in reproductive decisions. husbands) in reproductive decisions.

Modifying school curricula to include information on Modifying school curricula to include information on population levels and implications for the future.population levels and implications for the future.

Reforming tax laws in a way that encourages couples Reforming tax laws in a way that encourages couples to have no more than two children. (They would still to have no more than two children. (They would still be able to have as many kids as they want, but the tax be able to have as many kids as they want, but the tax code would no longer subsidize more than two.) code would no longer subsidize more than two.)

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