© 2011 Pearson Education, Inc.

AP Environmental Science

Mr. Grant

Lesson 6

Our World At Seven Billion

© 2011 Pearson Education, Inc.

Objectives:

• Define the term IPAT Model.

• Perceive the scope of human population growth.

• Assess divergent views on population growth.

• Evaluate how human population, affluence, and technology affect the environment.

© 2011 Pearson Education, Inc.

IPAT Model: A formula that represents how humans’ total impact (I) on the environment results from the interaction among three factors: population (P), affluence (A), and technology (T).

I = P x A x T

Define the term IPAT Model.

© 2011 Pearson Education, Inc.

Perceive the scope of human population growth.

It would take 30 years, counting once each second, to count to a billion! It would take 210 years to count to 7 billion!

Populations continue to rise in most countries, particularly in poverty-stricken developing nationsGrowth in poorer

nations leads to stresses on society, the environment,

and people’s well-being

China’s stringent policies have greatly slowed growth there, but other countries may wish to slow

their growth without the measures used

by China

© 2011 Pearson Education, Inc.

India’s growth continues and if not changed will surpass China’s population

© 2011 Pearson Education, Inc.

Exponential population growth…

It took until 1800 to reach 1 billion

130 years later) we reached 2 billion

We added the most recent billion in 12

years

© 2011 Pearson Education, Inc.

Rates of growth vary from region to region.

Some countries are over 3%, while other country’s populations are shrinking

current world growth rate is 1.2%

At this rate, the human population of the planet would double in 58.3 years

© 2011 Pearson Education, Inc.

Assess divergent views on population growth - Malthus.

Thomas Malthus’s An Essay on the Principles

of Population (1798)

Humans will outstrip food supplies

War, disease, starvation reduce

populations

© 2011 Pearson Education, Inc.

Assess divergent views on population growth - Ehrlich.

Neo-Malthusians: population growth will increase faster than food production; cause famine and conflict

Paul Ehrlich’s Population Bomb (1968) predicted that civilization would end by the end of the 20th century

© 2011 Pearson Education, Inc.

Is population growth a problem?

Cornucopians argue that we

will continue to find new

resources and technology to support people

there are finite resources Quality of life will suffer with unchecked growth

© 2011 Pearson Education, Inc.

Is population growth a problem?

© 2011 Pearson Education, Inc.

Some governments fear falling populations.

Policymakers believe population growth increases

economic, political, and military strength

But growth is correlated with poverty, not wealth

Strong, rich nations have low growth rates

Weak, poor nations have high growth rates

© 2011 Pearson Education, Inc.

Evaluate how human population, affluence, and technology affect the environment.

x S

Total impact (I) on the environment

Population (P) = individuals need space and resources

Affluence (A) = greater per capita resource use

Technology (T) = increased exploitation of resources, but also pollution controls and

renewable energy

Sensitivity (S) = how sensitive an area is to human pressure (e.g., arid land vs.

rainforest)

© 2011 Pearson Education, Inc.

Population is one of several factors that affect the environment.

Humans use 25% of Earth’s net primary production

Technology has increased

efficiency and reduced our strain

on resources, resulting in

further population growth

© 2011 Pearson Education, Inc.

Human population growth and regulation

© 2011 Pearson Education, Inc.

Human population growth and regulation