The Ecological Footprint The Ecological Footprint ModelModel

Is humanity outrunning the Is humanity outrunning the ecological capacity of the Earth to ecological capacity of the Earth to

sustain human life? sustain human life?

Pop Quiz 2 SolutionsPop Quiz 2 Solutions

Q: Why did we conclude that high school Q: Why did we conclude that high school GPA is a better predictor of college success GPA is a better predictor of college success than SAT?than SAT?

A: Because regression models that use high A: Because regression models that use high school GPA to predict college GPA school GPA to predict college GPA explain explain more variancemore variance than models that use SAT than models that use SAT

Pop Quiz 2 SolutionsPop Quiz 2 Solutions

Q:Q: Why did investigators look at the Why did investigators look at the unexplained variance for evidence of gender unexplained variance for evidence of gender bias?bias?

A:A: Because their regression models used all Because their regression models used all the other inputs that might explain salary the other inputs that might explain salary difference. If there was gender bias, it would difference. If there was gender bias, it would show up in the unexplained variance.show up in the unexplained variance.

What is sustainability?What is sustainability?

Humans living in a way that does not Humans living in a way that does not diminish Earth’s capacity to sustain lifediminish Earth’s capacity to sustain life

Alternatively: living within Earth’s ecological Alternatively: living within Earth’s ecological carrying capacitycarrying capacity

Are we going through a Are we going through a global ecological global ecological crisis?crisis?

Models, bias, and objectivityModels, bias, and objectivity

To create models, we must make To create models, we must make assumptionsassumptions

This introduces the possibility of This introduces the possibility of biasbias However, invalid models will not validate! However, invalid models will not validate!

(model predictions do not match reality)(model predictions do not match reality)

By rejecting incorrect ideas, we hope to By rejecting incorrect ideas, we hope to eventually discover objective realityeventually discover objective reality

What models cannot doWhat models cannot do

Inform us about our valuesInform us about our values Predict results of conscious human Predict results of conscious human

decisionsdecisions

Modeling goal Modeling goal

A single number to represent the fraction of A single number to represent the fraction of Earth’s ecological capacity being used Earth’s ecological capacity being used

If this number is more than 100%, humans If this number is more than 100%, humans are in trouble and must change our waysare in trouble and must change our ways

We can track this number to see trends We can track this number to see trends (better or worse) over time.(better or worse) over time.

Candidate: human population sizeCandidate: human population size

Ecology: the Ecology: the carrying capacitycarrying capacity for a species is for a species is the maximum population of that species the the maximum population of that species the environment can sustainably supportenvironment can sustainably support

Humans are different because their lifestyles can Humans are different because their lifestyles can vary (vary (e.ge.g. Americans . Americans vs.vs. Europeans Europeans vs.vs. Chinese) Chinese)

A high-consumption individual intuitively uses up A high-consumption individual intuitively uses up more ecological capacity than a low-consumption more ecological capacity than a low-consumption individualindividual

How to measure total ecological impact?How to measure total ecological impact?

Estimating total impactEstimating total impact

Model needs to “boil down” thousands of items we Model needs to “boil down” thousands of items we consume into a single meaningful numberconsume into a single meaningful number

Result is a type of Result is a type of indexindex

IPAT formula by Paul Ehrlich IPAT formula by Paul Ehrlich

Impact = Population x Affluence x TechnologyImpact = Population x Affluence x Technology

(I=PAT)(I=PAT) Population x Affluence = Total $ of Population x Affluence = Total $ of

consumptionconsumption Technology factor = how much ecological Technology factor = how much ecological

impact per dollar of consumption impact per dollar of consumption Doubling P, A, or T will double impactDoubling P, A, or T will double impact

IPAT formula by Paul Ehrlich IPAT formula by Paul Ehrlich

Technology factor : smaller is betterTechnology factor : smaller is better Consumption growth affects the Consumption growth affects the

environment more than population growthenvironment more than population growth Cannot calculate actual numbers, so it is Cannot calculate actual numbers, so it is

only a only a conceptual modelconceptual model

Ecological Footprint modelEcological Footprint model

Fundamental ecological “currency”: Fundamental ecological “currency”: productive land and sea areaproductive land and sea area

Every product measured in usage of four Every product measured in usage of four land area typesland area types

Total area used is the “Ecological footprint”Total area used is the “Ecological footprint” Can compare against known total Earth Can compare against known total Earth

productive area.productive area.

Components of a footprint Components of a footprint

Energy land (growing plants to soak up COEnergy land (growing plants to soak up CO22

output from fossil fuel consumption)output from fossil fuel consumption) Built up landBuilt up land Farm landFarm land Forest landForest land Footprint calculations are Footprint calculations are data-intensivedata-intensive

rather than rather than computation-intensivecomputation-intensive

Footprint CalculationFootprint Calculation

US Ecological FootprintUS Ecological Footprint

Global Ecological FootprintGlobal Ecological Footprint

1961: Total human footprint was 61% of 1961: Total human footprint was 61% of Earth’s productive land areaEarth’s productive land area

1998: Total human footprint was 135% of 1998: Total human footprint was 135% of Earth’s productive land areaEarth’s productive land area

Total footprint if each person lived US Total footprint if each person lived US lifestyle = 400% of Earth’s productive lifestyle = 400% of Earth’s productive capacitycapacity

Footprints and ecological EthicsFootprints and ecological Ethics

““We part the veil on our We part the veil on our killer sunkiller sun

Can’t keep the straight Can’t keep the straight path on this short runpath on this short run

The more we take, the The more we take, the less we become.”less we become.”

--Sarah Maclaclan, “World on Fire”--Sarah Maclaclan, “World on Fire”

The Ethical questionsThe Ethical questions

1.1. Is there a finite ecological space that we all Is there a finite ecological space that we all must share?must share?

2.2. If so, are we taking too much of this space If so, are we taking too much of this space away from other humans?away from other humans?

3.3. Are we taking too much ecological space Are we taking too much ecological space from other species?from other species?

Question #1 is factual, #2 and #3 are ethical Question #1 is factual, #2 and #3 are ethical (but depend on #1)(but depend on #1)