Creating a Sustainable Society:
Dynamics of Renewable
Resources
John Sterman
Jay W. Forrester Professor of Management and Engineering Systems
Director MIT System Dynamics Group
MIT Sloan School of Management
jsterman@mit.edu
web.mit.edu/jsterman/www
Fishbanks Debrief
Winslow Homer, Fishing Boats, Key West (1903)
Results from MIT Exec Ed
Overshoot and Collapse
Atlantic Swordfish Catch
Pacific Bluefin Tuna Catch
16
Thousand Metric Tons/year
Thousand Metric Tons/year
5
4
12
3
2
1
0
1950
8
4
0
1960
1970
1980
1990
2000
1950
1960
1970
1980
1990
2000
North Sea Herring Catch
Mark Wise, Common Fisheries Policy of the European Community, New York, Methuen, 1984.
Consider the Cod
• Northern or Atlantic Cod
–Long-lived, slow to mature
–Once immensely abundant
• Early fishers (e.g., Basque) claimed fish so dense
you could walk from Spain to the New World on
their backs.
• John Cabot, exploring Newfoundland in 1497, noted
fish so thick they practically blocked his ship.
–Harvest ≈ 250,000 metric tons/yr through 1950s
–Vital in feeding the Old World, in the
development of the New World,
…and of Massachusetts:
The Sacred Cod
Massachusetts State House
Prevailing Mental Model:
Unlimited Abundance
“Probably all the great fisheries are
inexhaustible; that is to say that
nothing we do seriously affects the
number of fish.”
– Thomas Henry Huxley, 1883
Source: US National Marine Fisheries Service
Estimated Cod Stocks, Scotian Shelf
(000 Metric Tons)
Estimated Biomass in 1852
1200
Estimated Carrying Capacity
(Myers et al. 2001)
800
400
Total Cod Biomass
Total Cod Biomass Age 5+
0
1850
1870
1890
1910
Rosenberg et al., Frontiers in Ecology, 2005
1930
1950
1970
1980
New England Fisheries - Hard Times
“I remember catching 5,000 pounds of fish in
eight nets. Today, it might take up to 80 nets.
Back then, the average codfish in the spring
would probably be 25 to 40 pounds. Now, it's 5
to 8 pounds.” - Peter Morse
“Go down to the docks and talk to the guys
down there,” said John Nelson, chief of the
Marine Fisheries Division of the state Fish and
Game Department. “Most of them have their
boats for sale. If they could sell their boats and
do something else, they would.”
Source: Clare Kittredge, "N.H. Fish Story Is Not a Happy One," Boston Globe. February 4, 1990.
• World “capture fishery” yield: 90
million tonnes, with first-sale value
of $94 billion (2008).
• Fish sector employs 45m people
directly, 180m indirectly, supporting
about 540m people (8% of world
population).
• More than 3b people today get 15%
or more of their animal protein from
fish.
• World “capture fishery” production
peaked in late 1990s and is falling.
• Total fish production growing due to
rise in aquaculture, but growth rates
slowing.
• Only 15% of fish stocks worldwide
considered “underexploited” or
“moderately exploited”, down from
40% in 1970s.
• World population (7b) projected to
exceed 9b by 2050; 10b by 2100.
UN FAO, State of the World Fisheries and Aquaculture 2010. http://www.fao.org/docrep/013/i1820e/i1820e00.htm
“The proportion of marine fish stocks estimated to be underexploited or moderately
exploited declined from 40 percent in the mid-1970s to 15 percent in 2008,
whereas the proportion of overexploited, depleted or recovering stocks increased
from10 percent in 1974 to 32 percent in 2008. The proportion of fully exploited
stocks has remained relatively stable at about 50 percent since the 1970s.”
UN FAO, State of the World Fisheries and Aquaculture 2010. http://www.fao.org/docrep/013/i1820e/i1820e00.htm
Overshoot and Collapse
Annual fish catch
Why the pervasive pattern of
overshoot and collapse of fisheries?
Where are the
leverage points for
creating a
sustainable fishery?
Where are they not?
Time
1. Renewable resources
Regeneration
Renewable
Resource
Harvest
2. Pollution and wastes
can be emitted no faster than natural systems can
absorb them, recycle them, or render them harmless.
Recycling,
Decay
Pollution,
Wastes
Waste
Generation
3. Nonrenewable
resources
Nonrenewable
Resource
can be used no faster
than renewable substitutes can
be introduced.
Nonrenewable
Resource
Extraction
Source: Herman Daly (e.g., H. Daly (1990) Ecological Economics 2, 1).
Human Activity
Ecosystem Services
can be used no faster than they regenerate.
Feedback structure Governing
Renewable Resources
Fish Stock
Net Recruitment
+
+
Catch
+
R1
+
Population
Growth
B2
Fishing
Effectiveness
Fractional Net
Recruitment
+
B1
Limits to
Growth
+
Fish Density
-
Maximum Fish
Stock
Catch per Ship
+
Fleet Size
Fractional Net
Recruitment (1/year)
Fractional Net Recruitment vs.
Fish Density
0
0
Fish Density, S/Smax
(Dimensionless)
1
Impact of Technology on Ship Effectiveness
Catch per Ship
(Fish/Ship/year)
High Technology
Low Technology
0
0
Fish Density, S/Smax
(Dimensionless)
1
Net Recruitment
(fish/year)
Net Recruitment vs. Fish Density
0
0
Fish Density, S/Smax
(Dimensionless)
1
Net Recruitment vs. Fish Density
Net Recruitment
(fish/year)
Reinforcing Feedback
Dominant (R1)
Balancing Feedback
Dominant (B1)
MSY
0
0
Unstable
Equilibrium
Fish Density, S/Smax
(Dimensionless)
1
Stable
Equilibrium
Overshoot and Collapse
Simulation:
Fleet (potential catch)
grows 2%/year
Overshoot and Collapse: Examples
• Carrying capacity of the Earth:
- climate change,
- ozone layer,
- ground water,
- agricultural soils,
- forests,
- etc.
• Borrowing to maintain lifestyle
• Speculative bubbles
(housing, tech stocks, art, etc.)
• Abusing trust and good will
- Misleading accounting
- Telephone Marketing
- False online reviews
• Drinking
“The Tragedy of The Commons”
Garrett Hardin. Science 1968; 162:1243-8.
G. Hardin,
1915-2003
Photo: 1986
The Tragedy of the Commons
“Each man is locked into a system that compels him to
increase his herd without limit—in a world that is limited.
Ruin is the destination toward which all men rush, each
pursuing his own best interest…”
“No technical solution can rescue us.…”
“We may well call it ‘the tragedy of the commons,’ using
the word ‘tragedy’ as the philosopher Whitehead used it:
‘The essence of dramatic tragedy is not unhappiness. It
resides in the solemnity of the remorseless working of
things.’
“Common Pool Resources”
• Easily Appropriable (Low barriers to access)
• Rival (What you take, I can’t)
EXAMPLES:
•
•
•
•
•
•
Pastures
Fish
Forests
Irrigation
Clean Air & Water
Climate
•
•
•
•
•
Roads and Highways
Parking Spaces
Views
Server Resources
Consumer Trust in Online
Reviews
Single Owner vs. Open Access Harvest
MEY
Revenue
$/year
MSY
pmax
pOA = 0
Costs
0
0
Fish Density, S/Smax
(Dimensionless)
1
Causes of Collapse (1)
Collapse of the carrying capacity can occur when
underlying resources are
Nonrenewable or
Renewable but Consumable or Degradable
Collapse is worse with
• Common pool resources (Tragedy of the Commons)
• Slow or limited regeneration potential
• Tipping points created by positive feedbacks
• Irreversibilities due to e.g.
 Trophic cascade
 Evolutionary impacts
Causes of Overshoot (2)
• Long Delays in
Changes in Resource level
Measuring resource level
Understanding causes
Recommending action
Implementing policies
Policy impact
(Physical/Biological delay)
(Perception delay)
(Research delay)
(Political/social delay)
(Political/social delay)
(Physical/Biological delay)
Note: Delays are partly physical and partly political and social. Those with
vested interests in the status quo often misrepresent the situation to delay
action (e.g. tobacco, lead in gasoline, toxics in food, climate change).
Limits to Privatization
• Moxnes (1998): Experiment similar to Fishbanks
but with perfect private property rights: no Tragedy of Commons
• 74% of subjects overbuilt fleets; average fleet 60% above optimal
• Average fish stocks 15% below optimal
• Average subject wealth 46% below optimal
• Subjects: Fishers, Fishing Resource Managers, Researchers
Typical subject behavior:
No uncertainty case
Moxnes, E. (1998) Not Only the Tragedy of the Commons: Misperceptions of Bioeconomics. Management Science, 44(9):1234-1246.
Professor Elinor Ostrom
Winner, 2009 Nobel Memorial Prize in Economic Sciences
Elinor Ostrom’s Optimism
“I would rather address the
question of how to enhance the
capabilities of those involved to
change the constraining rules of
the game to lead to outcomes
other than remorseless
tragedies…”
Design Principles for “Governing the Commons”
1. Clearly defined boundaries (effective exclusion of
external unentitled parties);
2. Rules adapted to local conditions;
3. Most appropriators can participate in the decisionmaking process;
4. Effective and independent monitoring available;
5. Graduated sanctions available to punish appropriators
who violate community rules;
6. Conflict resolution mechanisms easily accessible;
7. The self-determination of the community recognized by
higher-level authorities;
8. For large scale common-pool resources: organization
in the form of multiple layers of nested enterprises.
Turkey
Rule-Base for Alanya
•
•
•
•
List of eligible fishers each September
List all usable fishing spots
Assign spots by lottery – one per fisher
September – January: Each day each
fisher moves east to next spot
• January – May: Each day each fisher
moves west to next spot
Limits to privatization
• Enforcement
– Requires effective rule of law to enforce property rights.
– Conflict around equity, fairness.
• High discount rate (“Après moi, le déluge.”)
– Owners may find it in their interest to harvest unsustainably
• Irreducible externalities
– You can pen up your sheep, but your fish? Air? Water?
Climate?
• Dynamic complexity
– Difficulty of measuring resource stocks, consumption,
regeneration
– Long delays in detecting and responding to overexploited
resource
– Long recovery delays
– Nonlinearities, thresholds, ‘side effects’
Limits to social solutions
• High discount rate (“Après moi, le déluge.”)
• Enforcement
– Identifying and sanctioning free riders, poachers
– Setting a sustainable limit
– Political pressure to discredit the science to raise catch
limits
– Eroding Goals (“Shifting Baselines” syndrome)
• Dynamic complexity
– Difficulty of measuring resource stocks, replenishment
– Long delays in detecting and responding to overexploited
resource
– Long recovery delays
– Nonlinearities, thresholds, ‘side effects’
Preventing Overshoot:
Where the Leverage Points Are
1. Earlier effective signal of resource depletion and system health
– Requires sustained, serious scientific effort to assess stock levels,
ecosystem health, emerging threats (e.g., pollution, invasive species,
climate change),
– In partnership with appropriators and communities,
– Analogous to disease surveillance systems and programs in public
health.
But
–
–
–
–
Resource level often unobservable
Harvest not a reliable indicator of stock levels
Natural variability means safe harvest often << MSY and current take
Difficult to build and maintain trust among scientists, regulators,
appropriators, communities, and other stakeholders, particularly when
the resource is threatened.
Preventing Overshoot:
Where the Leverage Points Are
2. Harvest must be limited to regeneration
But
– Enforcement difficult; expensive
– Regeneration rate uncertain, variable, difficult to assess
– To rebuild an already-depleted resource requires harvest fall even
farther (so regeneration > harvest).
– Appropriators very clever in finding loopholes in particular
mechanisms:
• 200 mile territorial limit kept foreign fleets out of US/Canada waters; domestic fleets
expanded to fill gap, collapse fishery
• Fleet size limits are offset by better technology, more intensive fishing
• Limited fishing days offset by better technology, more intensive, dangerous fishing
• Quotas lead to increased bycatch
• Catch shares lead to industry concentration, squeeze out small players
– If the limit is set too high, the system collapses
•
•
•
•
•
Science opposed by fishery interests, delays or prevents implementation
Political pressure leads to catch limits set too high
Catch limits lag stock assessments
Normal ecological variability can tip system into collapse
Shifting Baselines (Eroding Goals)
Preventing Overshoot:
Where the Leverage Points Are
3. Reduce effectiveness of harvest technology
– Without factory ships, spotter aircraft, advanced gear and other
technologies, ship effectiveness drops as stocks drop, limiting
overfishing.
– Less effective technology balances the system at higher fish
population, productivity and profit.
– Low tech makes it more difficult for free riders to evade enforcement &
curtails evader-enforcer arms race
But
– Enforceable regulations required to ensure level playing field, fairness
across all appropriators
– Individual appropriators have strong incentive to boost harvest
productivity through technology
– Some innovations worsen working conditions (e.g., factory ships), but
some enhance safety & working conditions, but not fully separable
from catch-enhancing technology. Goal conflict.
Impact of Technology
Other Technologies
• Factory Ships
• Sonar, Radar, GPS
• Spotter Aircraft
• Weather Forecasts
• Remote Sensing
• Trawls
• Bottom Drags
• Dredging
• Purse Seines
• Long Lines (>50 miles)
Source: http://www.erin.utoronto.ca/~w3env100y/env/ENV100/hum/cod.htm
Factory Trawlers
Impact of Technology on Ship Effectiveness
Catch per Ship
(Fish/Ship/year)
High Technology
Signal of problem detected
Low Technology
0
0
Fish Density, S/Smax
(Dimensionless)
1
Successful Management of the Commons
• Renewable Resources
–
–
–
–
–
State Fish and Game licensing programs
Some fisheries, e.g., Maine Lobsters
National and state parks, conservation zones, land trusts
International Whaling Commission (effectiveness limited)
CITES (effectiveness limited)
• Pollutants:
– CFCs and Stratospheric Ozone (Montreal Protocol, as amended)
– Clean Air Act, Clean Water Act; Limits on other pollutants
– US SO2 cap and trade program
• Self-Regulation in commercial groups, guilds
– Mozarella di Bufala in Italy
– Mangos in Brasil
• Government regulation/oversight of privatization
–
–
–
–
–
–
Workplace health and safety regs (e.g., prohibition on child labor)
Traffic signals, speed limits, seat belts
Mandatory childhood immunizations
Public funding for police, fire protection, schools, defense, etc.
Do-not-call list for telemarketing
Congestion pricing (e.g. London, Stockholm)
Extra Slides
Fish Stock
Net Recruitment
+
+
Catch
R1
+
Population
Growth
+
Fleet
B2
Fishing
Effectiveness
Fractional Net
Recruitment
+
B1
Limits to
Growth
+
Fish Density
-
Maximum Fish
Stock
Catch per Ship
+
+ Revenue
R2
Total Costs
+
Fish Stock
Net Recruitment
+
+
Catch
R1
+
Population
Growth
+
B1
Limits to
Growth
Fish Density
-
Maximum Fish
Stock
B3
Investment
Catch per Ship
+
+
Profit
Fleet
B2
+
-
Costs
+
Fishing
Effectiveness
Fractional Net
Recruitment
Profitable Growth
+
+ Revenue
R2
Total Costs
+
Fish Stock
Net Recruitment
+
+
Catch
R1
+
Population
Growth
+
B1
+
Limits to
Growth
Fish Density
-
Profit
B3
Investment
R3
Catch per Ship
+
+
Technology Race
+
Fleet Productivity
(Technology)
+
B4
Innovate or Die
Maximum Fish
Stock
+
Fleet
B2
+
-
Costs
Fishing
Effectiveness
Fractional Net
Recruitment
Profitable Growth
- Pressure to
Innovate
+
Demand for Fish
+
B5
-
Demand
Response
Fish Price
+
B5
Supply
Response
+ Revenue
R2
Total Costs
+
Fish Stock
Net Recruitment
+
+
Catch
R1
+
Population
Growth
+
B1
Limits to
Growth
Fish Density
-
Profit
B3
Investment
R3
Catch per Ship
+
+
Technology Race
+
Fleet Productivity
(Technology)
+
B4
Innovate or Die
Maximum Fish
Stock
+
Fleet
B2
+
-
Costs
+
Fishing
Effectiveness
Fractional Net
Recruitment
Profitable Growth
- Pressure to
Innovate
+
Demand for Fish
+
-
+
B5
Demand
Response
R4
Fish Price
+
B5
Conspicuous
Consumption
Status Value
Supply
Response
+ Revenue
+
R2
Total Costs
+
Fish Stock
Net Recruitment
+
+
Catch
R1
+
Population
Growth
+
B1
Limits to
Growth
Fish Density
-
Profit
B3
Investment
R3
Catch per Ship
+
+
Technology Race
+
Fleet Productivity
(Technology)
+
B4
Innovate or Die
Maximum Fish
Stock
+
Fleet
B2
+
-
Costs
+
Fishing
Effectiveness
Fractional Net
Recruitment
Profitable Growth
- Pressure to
Innovate
+
Population
Population
Growth
+
+
R5
Demand for Fish
+
+
-
Demand
Response
Wealth
Economic
Growth
+
B5
R4
Fish Price
B5
Conspicuous
Consumption
R6
+
+
Status Value
Supply
Response
+ Revenue
+
R2
Total Costs
+
Fish Stock
Net Recruitment
+
+
Catch
R1
+
Population
Growth
+
B1
Limits to
Growth
Fish Density
-
Profit
B3
Investment
R3
Catch per Ship
+
+
Technology Race
+
B4
+
Fleet Productivity
(Technology)
+
Innovate or Die
Maximum Fish
Stock
+
Fleet
B2
+
-
Costs
+
Fishing
Effectiveness
Fractional Net
Recruitment
Profitable Growth
- Pressure to
Innovate
+ Revenue
R2
Total Costs
+
Fish Stock
Net Recruitment
+
+
Catch
R1
+
Population
Growth
+
B1
Limits to
Growth
Fish Density
-
Maximum Fish
Stock
B3
Investment
Catch per Ship
+
+
Profit
Fleet
B2
+
-
Costs
+
Fishing
Effectiveness
Fractional Net
Recruitment
Profitable Growth
+
Overshoot and Collapse
UN FAO, State of the World Fisheries and Aquaculture 2010. http://www.fao.org/docrep/013/i1820e/i1820e00.htm
Stable or Growing…so far:
UN FAO, State of the World Fisheries and Aquaculture 2010. http://www.fao.org/docrep/013/i1820e/i1820e00.htm
UN FAO, State of the World Fisheries and Aquaculture 2010. http://www.fao.org/docrep/013/i1820e/i1820e00.htm
UN FAO, State of the World Fisheries and Aquaculture 2010. http://www.fao.org/docrep/013/i1820e/i1820e00.htm
UN FAO, State of the World Fisheries and Aquaculture 2010. http://www.fao.org/docrep/013/i1820e/i1820e00.htm
UN FAO, State of the World Fisheries and Aquaculture 2010. http://www.fao.org/docrep/013/i1820e/i1820e00.htm
Catch per Capita Falling
• Wild Catch/capita stagnated in
1970, now falling at
accelerating rate
• Compensated (to date) by
rising aquaculture production
• Aquaculture growth slowing
worldwide, faces limits:
– Food supply (e.g., 5 Kg oceanic fish
converted to meal to yield 1 Kg shrimp)
–
–
–
–
–
Pollution (feces, BOD)
Toxics (e.g., dioxin accumulation)
Disease (requires antibiotics)
Coastal erosion, sedimentation
Genetic impact on wild stocks
(escapees)
UN FAO, State of the World Fisheries and Aquaculture 2010. http://www.fao.org/docrep/013/i1820e/i1820e00.htm
Fisheries Essential to World Food Security
• Undernourishment: “describes the status of persons whose food
intake regularly provides less than their minimum energy
requirements”
• Grain production not keeping pace with population in many regions
• More grain devoted to meat production to increase protein
Number of undernourished
people in the world
UN FAO, 2010. The State of Food Insecurity in the World. http://www.fao.org/publications/sofi/en/
Where did the big fish go?
The canneries were so efficient at processing
the lobsters that they were soon forced to
work with smaller lobsters.
In 1860, James P. Baxter recalled that four to
five pound lobsters were considered small
and the two pound lobsters were being
discarded as not worth the effort to pick the
meat for canning.
Only twenty years later, the canneries were
stuffing meat from half-pound lobsters into
the tins for processing.
— Gulf Of Maine Aquarium
Challenge the Boundary
•Conventional fishery models suggest
stocks will recover if total catch is
reduced below recruitment.
•This does not appear to be
happening in many depleted
fisheries.
•Why?
Evolution and Ecology
•Conventional theory:
• Ecological dynamics: Fast
• Evolutionary dynamics: Slow
•Modern View:
• Evolution often occurs on the same time scale
as ecological & epidemiological processes
central to public health and human welfare
• Antibiotic resistant Staph, Strep, TB, STDs, etc.
• Treatment resistant HIV
• Pesticide resistant insects & crop pathogens
• Size & maturation rate of fish
Mesh Size
Fishing
Effort
+
Fraction of
Largest Fish
Harvested
-
Average
Fish Size
Mesh Size
Time
Fishing
Effort
+
+
Fraction of
Largest Fish
Harvested
B1
Diminishing
Returns
-
Time
Average
Fish Size
Mesh Size
Time
+
Fishing
Effort
+
+
Fraction of
Largest Fish
Harvested
Time
R2
Tighten the
Noose
B1
Diminishing
Returns
-
Average
Fish Size
Time
Average Size
of Fish Caught
+
Time
+
+
Mesh Size
Time
Minimum
Permitted
Mesh Size
Fishing
Effort
+
+
Fraction of
Largest Fish
Harvested
R2
Tighten the
Noose
B1
Diminishing
Returns
-
Average
Fish Size
Time
Average Size
of Fish Caught
+
Time
+
+
Mesh Size
Time
Minimum
Permitted
Mesh Size
Fishing
Effort
+
+
R2
Fraction of
Largest Fish
Harvested
Tighten the
Noose
B1
+
Diminishing
Returns
+
Average Size
of Fish Caught
Average
Fish Size
Time
+
Average Size of
Mature Fish
+
R1
Selective
Pressure
Frequency of Genes
Favoring Large Size in
Reproductive Stock
Event level: the Headlines
Codfish
depleted
off Maine
Limits may follow
as cod diminishes
in Gulf of Maine
Restrictions could
Hurt local fishermen
Lobstermen
Snag record
38m pounds
Fishing banned
at Georges Bank
Local fishermen fear overcrowding
Hearing casts fishery as sinking ship
Loopholes found
In fishing rules
N.E. lawmakers seek boat buyback ideas
Feds approve boat buyback program
Hope to thin fishing fleet with $2m in incentives
Canada’s
Gunboat
Diplomacy
Chrétien to protect
Atlantic fish stocks
What Happened?
What caused the overshoot
and collapse?
Who was responsible?
Rebranding “Trash” Fish
•
•
•
•
Slimehead
Patagonian Toothfish
Whore’s eggs
Mud Crabs
*
*
*
*
“Orange Roughy”
“Chilean Sea Bass”
“Maine Sea Urchin”
“Peekytoe Crab”