1. Reviewing the “Tragedy of the Commons”

2. Example of Tragedy of Commons
Imagine a field of grass shared by 6 farmers, each with one cow

3. Each cow currently produces 20 liters of milk per day The carrying capacity of the commons is 8 cows. For each cow above 8, the milk production declines by 2 liters (due to overgrazing, there is less grass for each cow: less grass, less milk!).
Total daily milk production for the commons: 120 liters

4. I need a new tractor. Better graze another cow
Are the farmers satisfied with 1 cow apiece? Not if they are want more liters of milk (and more profit)!
I need a new tractor. Better graze another cow
Total daily milk production for the commons: 140 liters (7 cows)

5. Wait! If you can graze another cow, so can I.
We are now at the carrying capacity -- do we stop? Not if I can make a little more profit!
Wait! If you can graze another cow, so can I.
Total daily milk production for the commons: 160 liters (8 cows)

6. And so... ...Until there was no more grass for any of the cows The End
Me too!
Me too!
Me too!
Me too!
...Until there was no more grass for any of the cows
The End

7. Practice Questions…
1. Along with population growth, which of the following is a major root of the environmental problems caused by humans? [A] our exploitation & consumption of resources [B] our renewable energy initiatives [C] our reforestation projects [D] our sustainable development practices 2. One example of the tragedy of the commons can occur when several farmers share the same pasture for feeding sheep. The root cause of this tragedy is that [A] people are bad [B] sheep reproduce too quickly [C] the market cannot support too many farmers [D] the farmers believe that if I don’t use it then someone else will. [E] The cost of the sheep is lessened by bulk purchase power

8. Introduction to APES Studying the State of Our Earth
Textbook pages 2-11

9. Interactions between systems
Environmental Science
how nature works.
how the environment effects us.
how we effect the environment.
how we can live more sustainably without degrading our life-support system.

10. Examples of systems Environment Ecosystem Ecology
External conditions that affect living organisms
Ecosystem
Has both biotic (living) and abiotic
(non-living) components
Ecology
Study of relationships between living organisms and their environment (relationships between the biotic and the abiotic)

11. Humans alter natural systems more than any other species.
Environmental scientists monitor natural systems for signs of stress by looking at environmental indicators.

12. Environmental Indicators
Environmental indicators describe the health/quality of a system ( and the “ecosystem services” it provides)
Table 1.2 from textbook: “Five key global environmental indicators”
Indicator
Recent Trend
Outlook for future
Overall impact on environmental quality
Biological diversity
Large number of extinctions, extinction rate increasing
Extinctions will continue
Negative
Food production
Per capita production possibly leveling off
Unclear
May affect the number of people Earth can support
Average global surface temperature and CO2 concentrations
CO2 concentrations and temperatures increasing
Probably will continue to increase, at least short term
Effects are uncertain and varied, but probably detrimental
Human population
Still increasing, but growth rate slowing
Population leveling off. Resource consumption rates are also a factor
Resource depletion
Many resources being depleted at rapid rates. But human ingenuity frequently develops “new” resources, and efficiency of resource use is increasing in many cases
Unknown
Increased use of most resources has negative effects

13. Linear Growth Quantity increases by a constant amount per unit of time
1,2,3,4,5, … or 2, 4, 6, 8
When plotted on a graph, growth yields a fairly straight line
sloping upward (positive growth)
Sloping downward (negative “growth” or decreasing amounts)

14. Exponential Growth Growth yields a J- shaped curve
Describes the human population problem that disturbs the environment today
Fun Fact: Expected to see the population boom to 8.1 billion – 9.6 billion in 2050, then stabilize between billion by 2100.

15. “Rule of 70” How long does it take to double? Rule of 70 Resource use
Population size
Money in a savings account
Rule of 70
70 divided by the percentage growth rate = doubling time in years
70 / 7% means it takes ten years to double

16. Sustainable Development
Assumes the right to use the earth’s resources and earth capital to meet needs
It is our obligation to create sustainability
Environmentally sustainable societies meets basic needs of its people in a just and equitable manner without degrading the natural capital that supplies these resources.

17. Resources: a supply of something
Renewable
Non-Renewable
Potentially Renewable
Direct solar energy
Fossil fuels
Fresh air
Winds, tides, flowing water
Metallic minerals (iron, copper, aluminum)
Fresh water
Nonmetallic minerals (clay, sand, phosphates)
Fertile soil
Plants and animals (biodiversity)

18. Biodiversity Genetic Diversity Species Diversity Ecological Diversity
Variety in a genetic makeup among individuals within a single species
Species Diversity
Variety among the species or distinct types of living organisms found in different habitats of the planet
Ecological Diversity
Variety of forests, deserts, grasslands, streams, lakes, oceans, wetlands, and other communities

19. Environmental Degradation
Common Property Resources
Tragedy of the Commons
Resources owned by none, but available to all users free of charge
May convert potentially renewable resources into nonrenewable resources

20. Practice Questions… [A] The distinction between species
 3. What is genetic diversity?
[A] The distinction between species
[B] The variety of environments
[C] The genetic makeup of individuals
[D] The different genes from mating
[E] Hybrid species mating
4. What is used in order to calculate the doubling of a resource, population, money, etc.?
(A) Rule of 2 (C) Rule of 20
(B) Rule of 40 (D) Rule of 70 (E) Rule of 90

21. 5. Which of the following events has increased the impact of humans on the environment? I. Advances in technology II. Use of tools for hunting III. Reduced human population growth [A] I only [B] I and II only [C] I and III only [D] II and III only [E] I, II, and III

22. 6. Which statement regarding a global environmental indicator is not correct? [A] Concentrations in atmospheric carbon dioxide have been rising quite steadily since the Industrial Revolution. [B] World grain production has increased fairly steadily since 1950, but worldwide production of grain per capita has decreased dramatically over the same period. [C] For the past 130 years, average global surface temperatures have shown an overall increase that seems likely to continue. [D] World population is expected to be between 8.1 billion and 9.6 billion by [E] Some natural resources are available in finite amounts and are consumed during a one-time use, whereas other finite resources can be used multiple times through recycling.