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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

20

40

60

80

100

120

140

Number of planets

Res

po

nse

s

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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1015202530354045

Ecological Footprint

Avg = 19 acres

0 10 20 30 400

20

40

60

80

100

120

140

160

Acres of land to feed you

Res

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s

2

Ecological Footprint

Which resource would be easiest to change?

05

101520253035404550

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

2

4

6

8

10

12

Carrying capacity

Pop

ula

tion

Siz

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

2

4

6

8

10

12

14

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

Yie

ld i

n t

on

sY

ield

in

$

Max

imu

m E

con

om

ic Y

ield

Max

imu

m S

ust

ain

able

Yie

ld

En

d o

f P

rofi

t Z

on

e(O

pti

mal

eff

ort

in

th

e sh

ort

ter

m)

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