- Количество слайдов: 42
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 • • 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 km 3/year): – Not accessible runoff excluded – Accessible (12, 500 km 3/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
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
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 Þ∑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
A closer look – Step 2 • 8 Main land-use categories – Energy – Consumed land – Currently used land – Land of limited availability
A closer look: The landconsumption Matrix
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
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 CO 2 emissions released by the average Icelander’s fossil fuel consumption? Assume: Fossil fuel consumption 160 GJ/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 • • • 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 forming public opinion • Can be used comparatively – Nations, regions – Technologies, behaviors
Disavantages • • • Is static Assumes no changes in productivity Assumes equal productivity everywhere Requires more sectors? Requires more products?