The Human Population and Its Impact
Chapter 6
1. Clarify weebly stuff
2. Finish 1-3 Notes
3. Introduce Shoe Project
Due next Friday
4. Start Chapter 6 –
History of human population
5. HW read 6-2 to 6-4 tonight
6. Quiz tomorrow
7. TEST Thursday, I think
C.O. You’ll know how human population has changed over time and if the
Earth can sustain our rapidly growing population.
L.O. You’ll get into small groups after taking some notes and discuss
ramifications of current human population and if you agree or disagree with
Malthus’ assertions.
Are There Too Many of Us?
 Estimated 2.4 billion more people by 2050
 Currently 7+ Billion people living
• Earth reached that milestone October 31st,
 Are there too many people already?
 Will technological advances overcome
environmental resistance that populations face
 Should populations be controlled?
Are There Too Many of Us?
The World’s Most Typical Person (video)
Core Case Study: Are There Too
Many of Us?
 Will growing populations cause increased
environmental stresses?
 Quick Group Discussion & Share-out. What
environmental stresses might an increasing human
populations cause?
Infectious diseases
Biodiversity losses
Water shortages
Traffic congestion
Pollution of the seas
Climate change
6-1 How Many People Can the Earth Support?
 We don’t know. But….
• how long can we continue increasing the earth’s
carrying capacity for humans?
• without seriously degrading the life-support system for
humans and many other species?
Vegas, Baby, Vegas
 Early Human Population
• Anatomically Modern Humans appear in fossil record
~200,000 years ago in Africa
 Early Human Population
• About 70,000 yrs ago Toba Volcano erupted in Indonesia.
• Ash limited sun for nearly 6yrs
• Genetic Bottleneck suggests humans almost wiped out – DNA
suggests we owe our existence to 40 breeding pairs!
 Early Human Population
 Mostly hunter/gather populations existed before 10
• Populations were very small and had very little population
• Death rates and birth rates were both very high.
• Catastrophic population crashes were also possible.
 At about 10 kya – 8 kya, the population growth rate increased,
 Early Human Population
 “Neolithic Revolution”
• Transition from hunter/gather to agrarian (farming) societies
• With ag comes the end of nomadism.
 Occurred through the development of cultivation of animals
and plants
 Occurred in many different regions of the World
• Asia, Africa, North America, Melanesia, etc
 Early Human Population –
• The Fertile Crescent (Birthplace of Ag)
 Early Human Population –
• The Fertile Crescent of North America
• The Four Corners (AZ, NM, CO, UT)
Human Population Growth Continues but It Is
Unevenly Distributed
 Reasons for human population increase
• Movement into new habitats and climate zones
• Early and modern agriculture methods
• Control of infectious diseases through
• Sanitation systems
• Antibiotics
• Vaccines
Human Population Growth Continues but It Is
Unevenly Distributed
Human Population
Yrs to an Additional
Billion People
Human Population Growth Continues but It Is
Unevenly Distributed
 Population growth in developing countries is
increasing 15 times faster than developed countries
 By 2050, 97% of growth will be in developing
 Should the optimum sustainable population be
based on cultural carrying capacity?
Global Connections: UN World Population
Projections by 2050
Science Focus: How Long Can the Human
Population Keep Growing?
 Thomas Malthus (economist) and his take on population
growth: 1798
• Proposed humans growing exponentially & food couldn’t
keep up.
• Proven wrong… so far
 Humans have altered 83% of the earth’s land surface
 Can the human population grow indefinitely?
Science Focus: How Long Can the Human
Population Keep Growing?
Thomas Malthus’ beliefs – Continued
Population growth leads to poverty when the population increases faster than the food
Overpopulation leads to lower wages and a labor surplus, further exasperating poverty
Malthus believed that the Poor should incorporate “moral restraint” to curve their high
reproductive habits.
Poverty is to be blamed on the Poor. It’s the Poor's own fault that they are poor.
Malthus was skeptical that the Poor where capable of doing this
(Social Darwinism), and thus the Poor would remain poor.
He was opposed to welfare because it might encourage more poverty.
Science Focus: How Long Can the Human
Population Keep Growing?
Two of the more outspoken, and controversial Neo-Malthusians are
 Paul Ehrlich: The Population Bomb
 Seen as a “Doomsdayer” , proposes that unless immediate action is taken to control overpopulation,
series crisis's will ensue.
 “We can no longer afford merely to treat the symptoms of the cancer of population growth; the cancer
itself must be cut out. Population control is the only answer. The operation will demand many apparently
brutal and heartless decisions. The pain may be intense. But the disease is so far advanced that only with
radical surgery does the patient have a chance of survival”, quote in Schmidtz and Willott (2002),
Environmental Ethics; What Really Matters, What Really Works, Oxford University Press, New York, pg
 Garrett Hardin: “The Tragedy of the Commons”
 Author of the “Lifeboat Ethics. Quoting Goldfarb (2000) in his book Notable Selections in Environmental
Studies, Second Edition, Dushkin-McGraw Hill, Guilford, CN,)
“[Lifeboat ethics is] a world model in which the developed, affluent nations that control and use most of the
world’s resources are in a lifeboat while the struggling developed nations are floundering in the
surrounding ocean. He concludes that it is folly to try to rescue all the swimmers and suggests that
the ethically appropriate strategy is one of triage, by which the ‘haves’ permit the poorest and least
developed of the ‘have nots’ to drown in order to prevent the entire boat from sinking” (pp. 39-40).
Science Focus: How Long Can the Human
Population Keep Growing?
A contrasting academic camp to the Neo-Matlhusians are the
• Technological advances (e.g. in agriculture) and expansion of the market
economy will mitigate any problems presented by overpopulation.
• If there are more people, then we will discover/invent new ways to feed
them. Technology will help us better utilize our resources, cure diseases, etc.
 – Prominent among the Cornucopians is Bjørn Lomborg.
Altering Nature to Meet Our Needs
Reduction of biodiversity
Increasing use of the earth's net primary
Increasing genetic resistance of pest species and
disease-causing bacteria
Elimination of many natural predators
Introduction of potentially harmful species into
Using some renewable resources faster than they
can be replenished
Interfering with the earth's chemical cycling and
energy flow processes
Relying mostly on polluting and climate-changing
fossil fuels
Fig. 6-A, p. 124