7 Billion…and counting!

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History of Population Growth

1. How long will human population growth continue?

2. Why does the human population continue to grow?

History of Population Growth• Tech advances, mostly in agriculture and

industry, changed the ways people lived and triggered increases in population size.

• Prior to the Industrial Revolution, humans relied on hunting/gathering/and farming to survive.

Growth Over Time• The human population grew faster in the 20th

century than it ever has before.• WHY? Because of improvements in health and

hygiene, increased availability of food, advances in industry and science.

• It is projected that the human population will reach 7 billion people by the year 2015(Oops! 2011! Wait…we are there already!)

By the way…the study of populations is called demography.

Industrial Revolution

1. Sanitation1. Louis Pasteur – Germ Theory of disease.2. Improved living conditions – no more dumping human waste3. Decreased disease

2. Medical Technology1. Antibiotics and vaccines2. Knowledge of diseases, infections, etc.

3. Changes in Agriculture1. Shift to large scale agriculture. 2. Pesticides and fertilizers developed to improve yield.

Industrial Revolution = life improvements = population explosion.

Recent Trends in Population• Recent growth rate down, but

population up.• Infant mortality – the number of

babies out of 1,000 that die during their first year of life.

• Life expectancy – the average number of year an individual is expected to live.

• When babies have a greater chance for survival and adults live longer, a population is likely to grow!

Growth Rate• Population growth rates vary by

region. Some nations have negative population growth rates, meaning the population is getting smaller.

• Humans use technology to extend Earth’s carrying capacity for our species.

• Growth rate (click to link to an interactive map)

refers to how a population changes in size during a specific period of time.

Growth rate of human population

has slowed from 2.1% to about 1.2% since

the 1960s.

Why Study Population Growth?

• Scientists have been carefully monitoring the human population for many reasons.

1. Do we have the resources on this planet to provide for all people?

2. What impact do the people have on our environment and natural world?

3. What impact do we have on each other?

Describing the Human PopulationDemographers look at a variety of things when studying populations.

– Population size, population density, population distribution, fertility rates, survivorship, birth rates, death rates, etc.

• Population Size – Clearly, the size of the human population is changing every second.

• Population Density – describes how many people live per square mile or kilometer. – Using your current knowledge, explain where you think the human

population is dense and where population is less dense? • Population Distribution – In ecological terms, the human

population is clumped. What does this mean? The above combined give demographers a “snapshot” of what the

human population looks like at a specific time.

Demographers consider…

• Demographic Transition : A model that explains a population’s change from high birthrates and death rates to low birthrates and death rates– Pre-industrial stage: Birthrates and death rates are

high.– Transitional stage: Birthrates are high but death

rates are declining.– Industrial stage: Birthrates start to decline; death

rates stay low.– Post-industrial stage: Both birthrates and death

rates fall to low and stable levels.

Canada, Japan, United

States, and Europe have gone through the transition, but scientists are not sure if

other countries will follow suit.

When Studying Population Growth…Demographers Consider…• Social Factors: factors such as wealth and education can

affect a nation’s population growth and its resource use. • Developing Nations – refers to nations with moderate to

low income. Worldwide, more people live in developing nations. – Tend to have higher fertility rates, infant mortality, and death

rates. – Despite many negative factors, population growth is high in

developing nations. – There are programs that encourage “smart family planning”

to help curb population growth in these countries.

Predicting Population GrowthSome scientists predict

that there will be 9 billion people on

Earth by 2050, while others maintain that

the population will be closer to 10.5 billion.

How do we predict what will occur?

To Predict Growth Demographers Look At…

• Fertility Rate– Total fertility rate: the average number of children a female

member of a population has during her lifetime. – What factors could influence fertility rate? – Recently, total fertility rates have started to drop in several

nations. – Replacement fertility rate: the total fertility rate for a nation that

would keep its population size stable. This rate will defer due to death rates.

To Predict GrowthDemographers Look At…

• Age Structure– It describes the relative

numbers of organisms of each age within a population.

– It shows the proportion of those that are currently at reproductive age and those that could reproduce in the future.

– Helps demographers to predict how a population could change over time.

To Predict Population Growth Demographers Look At…

• Sex Ratios– Describes the number of males compared to the number of females in

a population. – Normally, for every 100 females born, there are 106 males born.

Why Be Concerned About the Human Population Size?

• We are using renewable resources faster than they can be replaced. Such as trees, water, and food crops.

• We are using non-renewable resources at a faster rate each year. Such as oil, coal, minerals, natural gas.

• We are polluting the land, water, and air at a faster rate than ever. There are more people producing more pollutants.

• So what do we do?

What An Impact!• Obviously it is difficult to control population

growth. It is in our nature as humans to reproduce and grow.

• What we can control is what we all do while we are on the planet.

• Because this is an environmental science course, we are going to look at the environmental impacts created by the human population. You will find that as we explore those, we will discover many social and economic impacts as well.

What Can Be Done?

1. What would you do to control population growth while still maintaining quality of life for the human population?

2. What environmental impacts occur as a result of the human population?