Title: Carrying Capacity, human appropriation and the Ecological Footprint
1Carrying Capacity, human appropriation and the
Ecological Footprint
Readings. Vitousek 1986, Postel et al, 1996,
rprogress.org optional Daly et al 1992
2Carrying 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?
3Carrying 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)
4Different 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?
5Categories 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
6Estimating 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?
7A 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
8Human 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
9Human 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
10Human 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
11Human 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.
12Human 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
13A 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
14Human 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
15Human 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
16- Conclusion
- Humans appropriate 30 of accessible RFWS
- Humans appropriate 23 of all RFWS
- Total runoff appropriated 54
17The 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)
18Measuring
- 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
19The Concept
20Core 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
21The Calculation
- 4 Steps
- Step 1.
- Consumption of various goods and services
- Measured in Kg consumed/capita
- C
22The 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
23Calculation
- 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
24Calculation
- 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.
25Calculation
- Sustainability factor
- EF/total land area available
- Should be smaller than 1
26Calculation a closer look
- Step 1. Consumption Items
- Food
- Housing
- Transportation
- Consumer goods
- Services
27Consumption Categories
28A closer look Step 2
- 8 Main land-use categories
- Energy
- Consumed land
- Currently used land
- Land of limited availability
29Land-use Categories
30Productivity
31A closer look The land-consumption Matrix
32Overview
33Results 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
34Regional footprints
35Some 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
36EF 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)
37EF 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
38Fun 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
39Fun 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
40Fun with footprints
- The ecological footprint of various modes of
transportation in Reykjavik - Ecological footprint of vegans vs others
- Ecological footprint of the University
41Advantages 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
42Disavantages
- Is static
- Assumes no changes in productivity
- Assumes equal productivity everywhere
- Requires more sectors?
- Requires more products?