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