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: 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 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:

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. 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 /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. 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 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: Hubbert curves from