renewable resources ecological footprintfaculty.wwu.edu/~shulld/esci...
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Renewable resources
• Why are they overused?• Announcements
– Exam 2 next Tuesday– Review for exam on Thursday– Study guide posted – bring on Thursday
• Ecological footprint assignment
Ecological Footprint
Avg = 4.4 planets
0 2 4 6 8 100
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Number of planets
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Ecological Footprint
Results of the experiment where you edited your footprint.Which resources had the largest effect on your ecological footprint?
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Ecological Footprint
Avg = 19 acres
0 10 20 30 400
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Acres of land to feed you
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Ecological Footprint
Which resource would be easiest to change?
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Living Natural Resources
“What is common to the greatest number gets the least amount of care.” - Aristotle
• Topics– Public goods and the Tragedy of the Commons– Solutions to the problem of public goods– Example
• Fisheries management and max. sustainable yield
By the end of class today…
• Understand the logic behind “The tragedy of the commons”
• Recognize how this logic relates to the overuse of public resources
• Consider possible solutions to the problem• Understand how to manage renewable
resources to maximize sustainable yield and economic yield
Hardin’s Tragedy of the Commons
• What is the Tragedy of the Commons?• Other “Commons” metaphors?• Is a good conscience really self eliminating?• How can coercion be good?
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Solutions to the tragedy of the commons?
• Regulate access to the resource• Privatize the resource• Goal: Internalize environmental externality
• Example: Fisheries
Annual catch records for fisheries
Source: State of the World Fisheries and Aquaculture, 2012. UN FAO
19Year
Aquaculture – impacts on wild catch
Source: State of the World Fisheries and Aquaculture, 2012. UN FAO
Maximum Sustainable Yield
MSY of ocean: 100-135 MT per yCurrent usage: ~130 MT per y
Problems:Very close to (or exceeding) MSYEffort focused on few speciesTen groups represent > 95% of catch~30% of world fisheries collapsed
Estimated value of global fisheries: > $1 trillion
From Garrison, Oceanography
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> 85% of stocks fully or over exploited
Declines in large predatory fish
From Myers and Worm 2003, Nature
Maximum sustainable yield
0 5 10 15 200
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Carrying capacity
Pop
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e (N
)
Maximum rate ofpopulation growth
r
Population growthrate = harvest rate
Optimum size for harvest
Logistic growth model
Time
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Northern Shrimp
Data from MA Dept. of Fish and Wildlife
Northern Shrimp
1930 1940 1950 1960 1970 1980 1990 20000
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ME NH MA Total
Gulf of Maine northern shrimp landings by fishing season (December to May).
Data from MA Dept. of Fish and Wildlife
MT (thousands)Pandalus borealis
Northern Shrimp MSY
MA Dept. of Fish and Wildlife (2002)
Maximum sustainable yield versus maximum economic yield
• Which would be lower (more conservative)– Maximum sustainable yield of a public resource?– Maximum economic yield of a private resource?
• Maximum economic yield!• MEY is lower than MSY due to
– Reduced costs and capital– Higher fish value
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Max. sust. yield vs. max. economic yield
Fishing effort
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Max
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Max
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Long-termmaximum profit
Cost of Effort
Biomass
Privatization vs. Regulation
• Ways to regulate a fishery– Limited entry into fishery– Gear limitation– Limited catch per fisher– Limited fishing season– Limited total allowable catch– Private ownership: Fishers regulate
• Example: Individual transferable quotas
• Advantages of the different strategies?
Changes in cod-fishing gear in New England
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Trawling tracks recorded byNMFS in G. of ME.
65,000 km2 draggedannually in the Gulf ofMaine.
41,000 km2 dragged onGeorges Bank
On average, every cm2
dragged 3 x per y
1994: Ground fishery closed due to over fishing and habitat destruction
Trawling tracks
Which is more important, preserving benthic habitats or fishers’ livelihoods?Film (on DVD)
Alaskan deep-water corals
Photos: Seattle Times
Diverse deep—water coral communities are diverse and provideessential fish habitat.
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Alaska Trawling Ban
Regulating fisheries
• Keys to sustainability– Eliminate gear that destroys fish habitat
(Bottom trawls, dynamite, cyanide)
– Limit access to sensitive fisheries and habitats– Reduce bycatch– Maximize economic value of catch– Address conflicts of interest– Internalize externalities
Analysis of catch data supports the use of individual transferable quotas
Note Y-axis is upside
down
No ITQ
With ITQ
Number ofITQ fisheriesBy 2003, 27% of fisheries
had collapsed (dropped 90%)
Science 2008
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Pros and cons of ITQs
• Pros– Incentive to fish near maximum economic yield– Reduced capitalization– Longer fishing seasons with higher-value catch
• Cons– Consolidation (ITQs purchased by large firms)– Can still be mismanaged leading to overfishing– Difficult to allocate ITQs – catch history, politics
Clear-cutting the seafloor
Avoiding the tragedy of the commons?
• Regulation or privatization?• Internalizing externalities