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/page80.htm
Humans are different… • Human carrying capacity is hard to define, because… • Technological changes affect food production • Complex social factors affect population
UN world population projections: • World population may have passed its inflection point in 1970. • Herman Kahn called this time TheYear 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-20n2-1.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/ecoftpr.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 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