Ecological Sustainability: what can models tell us?
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Transcript Ecological Sustainability: what can models tell us?
Ecological Sustainability:
what can models tell us?
CSCI 1210
Fall 2003
Note: please don’t forget the
online student evaluations!
What is sustainability?
Humans living in a way that does not
diminish Earth’s capacity to sustain life
Alternatively: living within Earth’s
ecological carrying capacity
Are we going through a global
ecological crisis?
Overshoot and collapse
Previous model
assumes carrying
capacity is constant
What if a severe
overshoot degrades the
environment?
Carrying capacity might
be permanently
reduced
Image:http://www.dieoff.com/page8
0.htm
Humans are different…
Human carrying capacity is hard to
define, because…
1. Technological changes affect food
production
2. Complex social factors affect
population
UN world population projections:
World population may have passed its
inflection point in 1970.
Herman Kahn called this time The Year Zero
World3:The Nightmare Scenario
World3 model created by MIT systems group for the Club of
Rome
Model updated, 1990
Graphic: www.dieoff.com
Malthus in, Malthus out!
Nonrenewable resources run out…
Capital is diverted to resource extraction
Less capital for agriculture
Yields fall, leading to famine and death
Is this realistic??
The Cornucopians
Economist Julian Simon bet
ecologist Paul Ehrlich that prices
of nonrenewable resources
would fall
Ehrlich lost and had to pay
Simon $1000
Cornucopians argue that human
ingenuity will surmount all “limits”
to growth.
http://www.cato.org/pubs/policy_report/cpr-20n21.html
Are there limits?
Simon and climatologist Steven Schneider
offered to bet Simon $1000 on each of 15
ecological indicators getting worse over time.
Simon declined this bet.
The limits to growth are not industrial
resources, but ecological resources
The real limit may be the ability of Earth
to absorb pollution
World3 model and pollution
Here is what happens when you increase the
initial stock of natural resources by 1000
times.
World3 model and pollution
This time there is no shortage of agricultural
inputs, but land fertility suffers because of
pollution.
The IPAT formula
I = PAT
Proposed by Paul Ehrlich
I = environmental
Impact
P = population
size
A = Affluence
T = Technology
factor
http://www.stanford.edu/group/CCB
/Staff/paul.htm
IPAT: a conceptual model
Population is not the only factor
An American has more environmental
impact than a Bangladeshi or Chinese
To reduce environmental impact we
must control P, A, T or all three
Problem with IPAT: no defined measure
of total impact I
Ecological Footprint model
Definition of total
impact:
Ecological fooprint
is the total land area
that would be
needed to support a
city, country, or other
population unit.
http://www.ire.ubc.ca/ecoresearch/e
coftpr.html
Results of Ecological footprint
Were everyone
on Earth to live as
an average North
American…
It would require
three Earths to
sustain this
lifestyle.
World3 Persistent Pollution
World3 pollution model
In World3, the world reacts to pollution
problems after the pollution has already
become a problem
Inevitable delays in inventing and
deploying technology cause overshoot.
Pollution technology is modeled as a
stock. You can add more technology but
cannot make qualitative changes.
Real-world pollution response
In order to avoid overshoot, societies try
to deal with pollution problems before
they become severe
In the long term, qualitative changes
(redesigning technology) is more
powerful than adding filters to the back
end of the smokestack
Ecological safety factor?
Many scientists believe that humans
should use at most 50% of Earth’s
ecological capacity
This gives us a safety margin in case
our calculations are off
It also leaves some room for other living
things to share our planet
The Big Question:
How much do humans
have to change in order to
live within Earth’s carrying
capacity?
And the answer is…
Ecological overload factor if every
Earthling comes up to US lifestyle: 3
Additional population increase from
6 to 9 billion:
1.5
Further improvement needed to
leave 50% of Earth alone
2
TOTAL IMPROVEMENT NEEDED:
9
What does this mean?
We need at least a 9-fold reduction in
the amount of pollution caused by each
dollar of economic activity
Design school: Factor Ten
Another design school: Zero Waste
Is Zero Waste possible?
Nature does it!
Bill McDonough: divide
materials into industrial
nutrients and ecological
nutrients
Recycle industrial nutrients
Compost biological nutrients
Voila! Future technology!
A Democracy Deficit?
Those most vulnerable are far away…
And have little power to promote change
Needed: effective planetary democracy
Struggle over the global trade system – the
front line of the battle to save the Earth?
Acknowledgements
DOE vs EIA Hubbert curves: http://www.dieoff.org/page177.htm
Hubbert curves from
http://www.hubbertpeak.com