Transcript Ecological footprint

Carrying Capacity, human
appropriation and the
Ecological Footprint
Readings. Vitousek 1986, Postel et al, 1996,
rprogress.org optional – Daly et al 1992
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?
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)
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?
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
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?
A closer look 1
Human 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
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
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
Human appropriation of the
Products of Photosynthesis
• Low Calculation:
– Consumption or production of grain
– Consumption by life-stock
– Forests
– Aquatic ecosystems
=> 3% of all NPP
Human appropriation of the
Products of Photosynthesis
• Intermediate calculation
– Includes what is co-opted by humans
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Cropland
Pasture land
Forests use and conversion
Others such as lawns, golf courses and gardens
=>19.9% of total NPP.
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
=>40% of terrestrial NPP, 25% of global NPP
A closer look 2
Human Appropriation of the products of
freshwater
• Objective:
• Assess how much of the Earth’s
renewable freshwater is realistically
accessible to humans
• Assess how much humans use directly
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)
=> We appropriate 26% of all EP
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%
Conclusion
• Humans appropriate
30% of accessible
RFWS
• Humans appropriate
23% of all RFWS
• Total runoff
appropriated 54%
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)
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
The Concept
Core footprint issues
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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
The Calculation
4 Steps
Step 1.
• Consumption of various goods and
services
• Measured in Kg consumed/capita
• C
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
Calculation
Step 3.
• Assess the land mass appropriated per
capita for the production of each
consumption item.
• Measured in hectare per capita
=> aa = C/P = (kg/capita)/(kg/ha) = ha/capita
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.
Calculation
• Sustainability factor
• EF/total land area available
• Should be smaller than 1
Calculation – a closer look
Step 1. Consumption Items
• Food
• Housing
• Transportation
• Consumer goods
• Services
Consumption Categories
A closer look – Step 2
• 8 Main land-use categories
– Energy
– Consumed land
– Currently used land
– Land of limited availability
Land-use Categories
Productivity
A closer look: The landconsumption Matrix
Overview
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
Regional footprints
Some results
• North American average 9,7 ha/person
• Total land required 9,7*6 billion
• Require 57 billion - only have 13 ha
productive (need 4 earths)
• Average footprint is 2,3 ha/person - need
13,8 billion ha
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)
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
Fun with footprints
1. How much ecologically productive land is
needed to sequester all the CO2 emissions
released by the average Icelander’s fossil fuel
consumption?
Assume:
Fossil fuel consumption 160GJ/cap/year
Productivity of energy land 100 GJ/HA
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 M^3 of wood
• Wood productivity 2,3 M^3/ha/yr
Fun with footprints
• The ecological footprint of various modes
of transportation in Reykjavik
• Ecological footprint of vegans vs others
• Ecological footprint of the University
Advantages of the concept
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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
Disavantages
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Is static
Assumes no changes in productivity
Assumes equal productivity everywhere
Requires more sectors?
Requires more products?