1. Unit 3: Human Impact
I Why is human population growth an environmental problem?
A. Causes of human population growth
1. Agricultural Revolution – people settle into communities and more people were needed for division of labor; more reliable food supply can support a larger population.
2. Industrial Revolution – In the early 20th century technological advancements led to improvements in medicine and sanitation allowing for an increased birth rate and decreased death rate.
3. Urbanization (development of cities) leads to economic and social development which influence human populations.

2. Unit 3: Human Impact
I Why is human population growth an environmental problem?
B. Effects of human population
1. Overcrowding – may lead to tension and crime.
2. Increased pollution – air, water, and land ALL
pollution problems relate back to overpopulation.
3. Decreased natural resources, especially
nonrenewable resources (available only in limited
amounts).
Ex. fossil fuels, minerals, metals
4. Increased land use – leads to loss of habitat for
other species.

3. Unit 3: Human Impact
I Why is human population growth an environmental problem?
C. Solution =
1. ZPG – zero population growth (birth rate = death rate).
a. Limit number of births per family by offering tax incentives
Ex. China
b. Make birth control and family planning more available.
c. Educate public and our political leaders.
2. Conservation – wise and careful use of resources
a. Twenty percent of the world’s population uses more than
fifty percent of the world’s resources.

4. Unit 3: Human Impact
I Why is human population growth an environmental problem?
b. People in developed countries (like the U.S.) can decrease
resource use by the 3 R’s:
i. Reduce – use less materials; for example, buying
products that have less packaging
ii. Reuse – use products more than once; for example,
bring lunch in Tupperware instead of one-use
containers
iii. Recycle – return products to be re-processed; for
example, old tires are used to make track surfaces
c. Sustainability – ensuring the availability of resources and a
stable environment for future generations.

5. Review Questions What were three causes of human population growth?
- agricultural revolution, industrial revolution, urbanization
Why does human population growth lead to increased pollution?
- Increased number of people create more waste products (water-
pesticides, land – garbage, air – waste from factories) and use
more resources to produce consumables.
How do people, particularly those in developed countries, need to lessen the impact of human population growth?
- Conservation of resources (reduce, reuse, recycle)

6. Unit 3: Human Impact
II.How do local problems affect global conditions?
Global Warming
Cause: Excessive greenhouse gases (CO2 and CH4) in the atmosphere trap heat, leading to an abnormal increase in earth’s surface temperature
a. CO2 comes from burning fossil fuels in power plants, factories, and cars. Map shows top 10 production countries
b. CH4 comes from bacteria in landfills and cow farts
Effects: With just a small increase in temperature (2-4 degrees Celsius), weather patterns will change worldwide. Polar ice caps may melt, flooding coastal cities and contaminating drinking water with saltwater.

7. Global Warming Animation
Global Warming in short

8. Unit 3: Human Impact How do local problems affect global conditions?
B. Ozone Depletion
Cause: CFCs, once used as refrigerants and in aerosol cans,escape to the upper atmosphere and destroy many ozone molecules. This leads to a “hole”, or thinning, of the ozone layer. The CFCs can last decades, even though now banned.
Effects: A thinner ozone layer allows harmful UV radiation to reach earth’s surface causing increased incidence of sunburn, skin cancer, cataracts (leading to blindness), and crop damage.
Note: Ozone is “good” up high; “bad” nearby. This means ozone in the upper atmosphere blocks harmful UV rays, but ozone in the lower atmosphere (near us) causes respiratory ailments and damage to plant life.

9. Unit 3: Human Impact How do local problems affect global conditions?
C. Acid Precipitation
Cause: Harmful emissions from cars and factories
(especially nitrous oxide and sulfur oxide) react with
oxygen and water to make precipitation (rain, etc) more
acidic (pH less than 5.6)
Effects: A lowered pH disrupts aquatic ecosystems,
makes soil less fertile, harms plant life, and damages
human property.

10. Unit 3: Human Impact How do local problems affect global conditions?
D. Water Quality
Cause: Sources of water pollution often
begin on land, such as oil from cars, sediments from
naked land, and fertilizers from lawns. Other sources
include illegal chemical dumping, acid rain, overheated
water from power plants, and raw sewage.
Effects: A lack of clean drinking water is a leading
cause of disease (such as cholera, dysentery, typhoid).
Water pollution also affects many ecosystems through
habitat destruction.

11. Review Questions What are the two main greenhouse gases?
- carbon dioxide (CO2) and methane (CH4)
How are the effects of global warming different from the effects of ozone depletion?
- Global warming results from the buildup of greenhouse gases in the atmosphere, trapping heat and causing an increase in global temperatures, altering weather patterns.
- Ozone depletion results from pollutants (CFC) which destroy good ozone in the causing harmful UV radiation to enter our atmosphere. This causes increase skin cancer risks and crop damage.
Explain how car exhaust can contribute to acid precipitation?
- harmful emissions (nitrous and sulfur oxides) react with oxygen and water to lower the pH of precipitation.
Give an example of how land pollution contributes to water quality?
- Illegal dumping by industry or individuals that contaminate water sources. Run-off of pesticides into bodies of water.

12. Unit 3: Human Impact
III. How do humans negatively impact other species?
Biodiversity – the number of different species of
organisms that exist within an area and the genetic
diversity within each species
B. Causes of Biodiversity Loss:
1. Habitat Destruction
a. Deforestation – forests are cut down for
timber, agriculture, and development
b. Fragmentation – natural territories are broken
into areas too small to support native
populations
c. Draining/Filling Wetlands – for agriculture
and development

13. Unit 3: Human Impact
III. How do humans negatively impact other species?
2. Biomagnification of Pesticides
a. Rachel Carson, in her book Silent Spring,
wrote about the dangers of pesticide
contamination
b. Bioaccumulation – the build up of certain
pesticides in the tissues of organisms (Ex.
DDT in fish)
c. Biomagnification – increasing
concentration as pesticides move up the
food chain (Ex. DDT in bald eagles)

14. Unit 3: Human Impact
III. How do humans negatively impact other species?
Effects of Biodiversity Loss:
1. Endangerment/Extinction of Species
a. Endangered species are at risk of
becoming extinct. Extinction refers to the loss of a particular species.
b. The Endangered Species Act provides
protection for species recognized and
listed by the government. This Act does
not, however, provide adequate protection of the habitat.
2. Loss of valuable medicinal or crop plants, and
other species that may be potentially useful to
humanity
3. Lack of genetic variety makes crops more
susceptible to disease, pests, and environmental
changes

15. Unit 3: Human Impact What can you do to protect the environment?
A. Awareness – understand that each human has an
impact on his/her environment, and that because
our population is so large we have an ENORMOUS impact at the global level. “We cannot all do
everything, but we can all do something.”
B. Specific suggestions:
1. Reduce dependence on fossil fuels
(Example – car pool, support “green power”)
2. Recycle whenever possible
3. Limit use of chemicals at home
4. Consumer choices – supporting businesses
that are environmentally friendly, etc.
5. Political activism – Supporting candidates
and legislation which are environmentally
sound.

16. Review Questions What is biodiversity and why is it important?
the number of different species of organisms that exist within an area and the genetic diversity within each species. It is important to maintain the health of an ecosystem.
What is the difference between bioaccumulation and biomagnification?
- Bioaccumulation is the buildup of toxins in an individual organism.
- Biomagnification is the increased concentration at each higher trophic level. Ex. Herbivore (low concentration) vs. tertiary consumer (high concentration)
What is the weakness of the Endangered Species Act?
- It does not protect the habitat of the organism.
4. Rank the specific suggestions in order of importance. Give a reason for your choices.

17. Unit 3: Human Impact
V. What technology and techniques are used to study human impact on the environment?
Global imaging – scientists use satellites to track
changes global temperature and the ozone layer
Ice core analysis – analyze ice formed long ago to
determine the greenhouse gases present in the atmosphere at that time
C. Census data – demographers construct histograms to use in predicting future population growth trends (field called “demography”)
2. Developed and Stable
(Ex. United States)
3. Developed and Decreasing
(Ex. Germany)
Developing and Growing (Ex. Sudan)
(from

18. Review Questions
What two global conditions does global imaging help track?
ozone layer and global temperatures
2. Which histogram most accurately reflects the US population? #2