Carrying Capacity, human appropriation and the Ecological Footprint

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Carrying Capacity, human appropriation and the
Ecological Footprint
Readings. Vitousek 1986, Postel et al, 1996,
rprogress.org optional Daly et al 1992
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Carrying Capacity

• Upper limit to the ultimate size - carrying
  capacity (CC)
• Logistic or density dependent growth
• Growth determined by
• Pt Pt-1 r Pt-1 (CC - Pt-1)/CC
• Can we measure cc?
• Does it make sense to measure CC?

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Carrying Capacity

• Definition The maximum population of a species
  an area can support without reducing its ability
  to support the same species in the future
• Function both of the area and the organism (ex.
  Ceteris paribus Larger area higher cc)

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Different CC for different species

• Human carrying capacity
• Complicated by individual differences in the
  amount and quality of resources consumed and the
  evolution in the types and quantity of the stuff
  we consume.
• Issues?
• Is it static?

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Categories of CC

• Biophysical carrying capacity
• Maximum population size that could be sustained
  biophysically given certain technological
  capabilities
• Social carrying capacity
• maximum population that can be sustained under
  varying social systems.
• Smaller than biophysical cc

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Estimating CC

• Total area times productivity/ccal needed to
  survive (e.g.)
• Total area times productivity of that area
  divided by total kcal required to survive.
• How many calories people need to survive.
• 5.9 billion people.
• Useful? Realistic? Are we already appropriating
  too much?

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A closer look 1Human appropriation of the
products of photosynthesis

• Vitousek et al. 1986
• Examined the impact on the biosphere by
  calculating the NPP (Net primary production) that
  humans have appropriated
• Seminal study

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Human appropriation of the products of
photosynthesis

• NPP is the amount of energy left after
  subtracting the respiration of primary producers
  from the total amount of energy that is fixed
  biologically through photosynthesis
• Total food resource on the earth

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Human appropriation of the Products of
Photosynthesis

• Three calculations
• Low estimate The NPP used directly for food,
  fuel, timber or fibers
• Intermediate estimate The productivity of land
  that is entirely devoted to human activities
• High estimate The above and productive capacity
  lost due to land conversion

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Human appropriation of the Products of
Photosynthesis

• Low Calculation
• Consumption or production of grain
• Consumption by life-stock
• Forests
• Aquatic ecosystems
• gt 3 of all NPP

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Human appropriation of the Products of
Photosynthesis

• Intermediate calculation
• Includes what is co-opted by humans
• Cropland
• Pasture land
• Forests use and conversion
• Others such as lawns, golf courses and gardens
• gt19.9 of total NPP.

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Human appropriation of the Products of
Photosynthesis

• High calculation
• Includes losses in productivity
• Replacement of natural ecosystems with
  agricultural systems
• Forest conversion to pasture
• Desertification
• Areas occupied by humans
• gt40 of terrestrial NPP, 25 of global NPP

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A closer look 2Human Appropriation of the
products of freshwater

• Objective
• Assess how much of the Earths renewable
  freshwater is realistically accessible to humans
• Assess how much humans use directly

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Human Appropriation of the Products of Freshwater

• Terrestrial renewable freshwater Precipitation
  Evapotranspiration Eventual runoff to the sea
• Evapotranspiration (EP) Based on how much of NPP
  we use (use high estimate)
• gt We appropriate 26 of all EP

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Human Appropriation of the Products of Freshwater

• Total runoff (40,700 km3/year)
• Not accessible runoff excluded
• Accessible (12,500 km3/year)
• Withdrawals, consumption (we use 36 of all)
• Instream uses (we use 18 of all)
• Total appropriated 54

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• Conclusion
• Humans appropriate 30 of accessible RFWS
• Humans appropriate 23 of all RFWS
• Total runoff appropriated 54

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The ecological footprint

• Is a measure of the load imposed by a given
  population on nature.
• Represents the land area required to sustain a
  given level of resource consumption and waste
  discharge by that population
• The land area required to provide the energy and
  material requirements by the economy (measured in
  ha)

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Measuring

• The land required to sustain a particular human
  population - that is the area of land of various
  classes that is required on a continued basis to
  
• Provide all the energy and material resources
  consumed
• Absorb all the wastes that assimilate

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The Concept
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Core footprint issues

• Current industrial practices are sustainable
• Include only basic natural services
• Try not to double count
• Simplify the ecological productivity values
• Not really account for marine areas

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The Calculation

• 4 Steps
• Step 1.
• Consumption of various goods and services
• Measured in Kg consumed/capita
• C

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The Calculation

• Step 2.
• Assess the productivity of each land category
  required (given in program)
• Defined as how much land area is required to
  produce a particular amount
• Use global averages
• Measured in kg/ha
• P

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Calculation

• Step 3.
• Assess the land mass appropriated per capita for
  the production of each consumption item.
• Measured in hectare per capita
• gt aa C/P (kg/capita)/(kg/ha) ha/capita

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Calculation

• Step 4.
• Sum over all aa to get total EF
• ?aa, giving EF per capita per population
• Then of course you can multiply the total EF per
  capita by total population to get EF per nation.

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Calculation

• Sustainability factor
• EF/total land area available
• Should be smaller than 1

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Calculation a closer look

• Step 1. Consumption Items
• Food
• Housing
• Transportation
• Consumer goods
• Services

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Consumption Categories
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A closer look Step 2

• 8 Main land-use categories
• Energy
• Consumed land
• Currently used land
• Land of limited availability

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Land-use Categories
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Productivity
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A closer look The land-consumption Matrix
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Overview
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Results in a global context

• United States 9.7 ha/capita
• Canada 8.4 ha/capita
• - NS - 8.1 ha/capita
• - AB - 7.9 ha/capita
• France 5.3 ha/capita
• Japan 4.8 ha/capita
• Zimbabwe 1.3 ha/capita
• Bangladesh 0.5 ha/capita
• Global Average 2.3 hectares/capita

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Regional footprints
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Some results

• North American average 9,7 ha/person
• Total land required 9,76 billion
• Require 57 billion - only have 13 ha productive
  (need 4 earths)
• Average footprint is 2,3 ha/person - need 13,8
  billion ha

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EF Applications

• Region (country, province, town, university
  campus)
• Personal Ecological Footprint (redefining
  progress, mountain equipment co-op)
• Competing technologies (fuel cells)
• Growing Techniques (field tomato vs. hydroponic
  tomato)
• Policy decisions (rail vs. road, urban planning
  decisions)
• Purchase decisions (cradle to grave)
• Other (big mac, aquaculture, newspaper)

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EF in Use

• Teach concepts of sustainability, environmental
  issues, responsibility.
• Benchmark of School Sustainability (define
  current state, assess progress -- footprint
  increase? Footprint decrease?)
• Means of Comparison (between schools, between
  grades, students vs. teachers)
• Promote holistic decision making

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Fun with footprints

• How much ecologically productive land is needed
  to sequester all the CO2 emissions released by
  the average Icelanders fossil fuel consumption?
• Assume
• Fossil fuel consumption 160GJ/cap/year
• Productivity of energy land 100 GJ/HA

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Fun with footprints

• How much area do you need to produce paper for
  the average Icelander?
• 113 kg paper/cap/yr
• Each metric ton requires 1,8 M3 of wood
• Wood productivity 2,3 M3/ha/yr

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Fun with footprints

• The ecological footprint of various modes of
  transportation in Reykjavik
• Ecological footprint of vegans vs others
• Ecological footprint of the University

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Advantages of the concept

• Is clear and understandable
• Are we living beyond our means?
• Can be used in the Local Agenda 21 process
• Can be used as a benchmarking tool
• Can be used to public relations, information,
  motivation or for forming public opinion
• Can be used comparatively
• Nations, regions
• Technologies, behaviors

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Disavantages

• Is static
• Assumes no changes in productivity
• Assumes equal productivity everywhere
• Requires more sectors?
• Requires more products?