carrying capacity, natural capital, and ecological footprints
by William E. Rees, The University of British Columbia
WHY CARRYING CAPACITY?
According to Garrett Hardin (1991), "carrying capacity is the fundamental basis for demographic accounting." On the other hand, conventional economists and planners generally ignore or dismiss the concept when applied to human beings. Their vision of the human economy is one in which "the factors of production are infinitely substitutable for one
another" and in which "using any resource more intensely guarantees an increase in output" (Kirchner et al., 1985). As Daly (1986) observes, this vision assumes a world "in which carrying capacity is infinitely expandable" (and therefore
irrelevant). Clearly there is great division over the value of carrying capacity concepts in the sustainability debate.
Definitions: Carrying Capacity and Human Load
For purposes of game and range management, carrying capacity is usually defined as the maximum population of a given species that can be supported indefinitely in a defined habitat without permanently impairing the productivity of that habitat. However, because of our seeming ability to increase our own carrying capacity by eliminating competing
species, by importing locally scarce resources, and through technology, this definition seems irrelevant to humans. Indeed, trade and technology are often cited as reasons for rejecting the concept of human carrying capacity out of
hand. [According to orthodox theory, free trade is invariably good, resulting in improved living standards and increased aggregate productivity and efficiency -- increased carrying capacity -- through comparative advantage.]
This is an ironic error -- shrinking carrying capacity may soon become the single most important issue confronting humanity. The reason for this becomes clearer if we define carrying capacity not as a maximum population but rather as
the maximum "load" that can safely be imposed on the environment by people. Human load is a function not only of population but also of per capita consumption and the latter is increasing even more rapidly than the former due
(ironically) to expanding trade and technology. As Catton (1986) observes: "The world is being required to accommodate not just more people, but effectively 'larger' people . . ." For example, in 1790 the estimated average daily energy consumption by Americans was 11,000 kcal. By 1980, this had increased almost twenty-fold to 210,000 kcal/day (Catton 1986). As a result of such trends, load pressure relative to carrying capacity is rising much faster than is implied by mere population increases.
The Ecological Argument
Despite our technological, economic, and cultural achievements, achieving sustainability requires that we understand human beings as ecological entities. Indeed, from a functional perspective, the relationship of humankind to the rest of the ecosphere is similar to those of millions of other species with which we share the planet. We depend for both basic needs and the production of artifacts on energy and material resources extracted from nature and all this energy/matter is eventually returned in degraded form to the ecosphere as waste. The major material difference between humans and other species is that in addition to our biological metabolism, the human enterprise is characterized by an industrial metabolism. In ecological terms, all our toys and tools (the "capital" of economists) are "the exosomatic equivalent of
organs" (Sterrer, 1993) and, like bodily organs, require continuous flows of energy and material to and from "the environment" for their production and operation. It follows that in a finite world:
* Economic assessments of the human condition should be based on, or at least informed by, ecological and biophysical analyses.
* The appropriate ecological analyses focus on the flows of available energy/matter (essergy) particularly from primary producers--green plants and other photosynthesizers -- to sequential levels of consumer organisms in ecosystems (specifically, humans and their economies) and on the return flows of degraded energy and material (wastes) back
to the ecosystem.
This approach shows that humankind, through the industrial economy, has become the dominant consumer in most of the Earth's major ecosystems. We currently "appropriate" 40% of the net product of terrestrial photosynthesis (Vitousek et al., 1986) and 25-35% of coastal shelf primary production (Pauly & Christensen, 1995), and these may be unsustainable proportions. [Global fisheries yields have fallen since 1989.] At the same time some global waste sinks seem full to overflowing.
A fundamental question for ecological economics, therefore, is whether the physical output of remaining species populations, ecosystems, and related biophysical processes (i.e., critical self-producing natural capital stocks), and the waste assimilation capacity of the ecosphere, are adequate to sustain the anticipated load of the human economy into the next century while simultaneously maintaining the general life support functions of the ecosphere.
This "fundamental question" is at the heart of ecological carrying capacity but is virtually ignored by mainstream analyses.
Approptiated Carrying Capacity and Ecological Footprints
We can now redefine human carrying capacity as the maximum rates of resource harvesting and waste generation (the maximum load) that can be sustained indefinitely without progressively impairing the productivity and functional integrity of relevant ecosystems wherever the latter may be located. The size of the corresponding population would be a function of technological sophistication and mean per capita material standards (Rees, 1988). This definition reminds us
that regardless of the state of technology, humankind depends on a variety of ecological goods and services provided by nature and that for sustainability, these must be available in increasing quantities from somewhere on the planet as
population and mean per capita resource consumption increase (see also Overby, 1985).
Now, as noted earlier, a fundamental question for ecological economics is whether supplies of natural capital will be adequate to meet anticipated demand into the next century. Inverting the standard carrying capacity ratio suggests a
powerful way to address this critical issue. Rather than asking what population a particular region can support sustainably, the carrying capacity question becomes:
How large an area of productive land is needed to sustain a defined population indefinitely, wherever on Earth that land is located? (Rees, 1992; Rees & Wackernagel, 1994; Wackernagel & Rees, 1995). Since many forms of natural income (resource and service flows) are produced by terrestrial ecosystems and associated water bodies, it should be
possible to estimate the area of land/water required to produce sustainably the quantity of any resource or ecological service used by a defined population at a given level of technology. The sum of such calculations for all significant
categories of consumption would give us a conservative area-based estimate of the natural capital requirements for that population.
Directions
So how can you personally have an impact on the sustainability of the environment? The first thing you should do is to recognize how you contribute directly or indirectly to the problem. Then you need to figure out how you can reduce your impact and increase your green practices.
You can do all of this by knowing your ecologocial or carbon footprint.
What is your ecological footprint?
Your ecological footprint is the total amount of greenhouse gases produced by human activities. It is measured in units of carbon dioxide.
Your task will be to better understand the Ecological Footprint and learn how you can reduce your personal footprint.
Go to the Global Footprint Network
Go to the top of the page and find the section called Footprint Basics. Find "Overview" in the drop down screen. Answer the following questions in your notebook or a word document
"Describe basically what an ecological footprint is and what it measures".
From the menu on the left, find the "World Footprint link". Answer the following questions in your notebook.1) Describe the growth of the world ecological footprint from 1960-2007; 2) Describe and explain the two potential ecological footprint models for the year 2050; 3) What is overshoot?
Go back to the Overview. On the menu find "Footprint For Nations". From the "Country Trends" box, select "United State of America". Answer the following questions in your notebook. 1) What year was the United States’ ecological footprint and biocapacity equal; 2) Describe the growth trends of the ecological footprint and biocapacity; 3) What are the three major factors that account for an individual’s ecological footprint (in hectares per person)?; 4)List the ecological footprint for a U.S. citizen in the following years- 1961, 1973, 1985, 2001, 2005.
Go back to the drop down menu of "Footprint For Nations" and select "Japan" . Answer the following questions in your notebook.
1) How does Japan’s ecological footprint compare to its biocapacity overall; 2) When will Japan’s biocapacity and ecological footprint equalize?; 3) How does a Japanese citizen’s ecological footprint compare to someone from the U.S. in the year 2005?
Go back to the drop down menu of "Footprint For Nations" and select "Chile". Complete the following questions in your notebook.
1) How does Chile’s biocapacity compare to its ecological footprint overall?; 2) What to you think this says about Chile’s long term sustainability compared to the U.S. or Japan?; 3) Estimate the average ecological footprint (in hectares per person) for a resident of Chile from 1961 to 2005.
Go back to the "Overview". Now go to the left hand links and find Carbon footprint. Answer the following questions in your notebook.
1) How much of the ecological footprint is represented by the "Carbon Footprint"?; 2) Typically the carbon footprint refers to emissions. How is the carbon footprint here utilized in a different way as incorporated into the model?; 3) How do carbon emissions exemplify the "tragedy of the commons"?
Go back to the "Overview". Now find the Personal Footprint link and complete the Quiz. Answer the following questions in your notebook.
1) What was your ecological footprint according to the model in terms of the number of Earth’s necessary to sustain you lifestyle? Did this surprise you? Why or why not?; 2)How many global acres of Earth’s productive area are required? Tons of Carbon Dioxide?; 3) List the percentage breakdown for each of the five categories in the pie chart for your ecological footprint.
Click on the explore scenarios button on your Footprint page….Click on at least two of the "What if" selections and then click "OK". Describe the two actions you chose, and the effect on your ecological footprint. Record this information in your notebook.
Click "OK" one more time, and when prompted click on the "Save Footprint" button….you’ll need to enter a valid email address and pick a password. Now you can access your footprint any time.
Congratulations on a job well done
WHY CARRYING CAPACITY?
According to Garrett Hardin (1991), "carrying capacity is the fundamental basis for demographic accounting." On the other hand, conventional economists and planners generally ignore or dismiss the concept when applied to human beings. Their vision of the human economy is one in which "the factors of production are infinitely substitutable for one
another" and in which "using any resource more intensely guarantees an increase in output" (Kirchner et al., 1985). As Daly (1986) observes, this vision assumes a world "in which carrying capacity is infinitely expandable" (and therefore
irrelevant). Clearly there is great division over the value of carrying capacity concepts in the sustainability debate.
Definitions: Carrying Capacity and Human Load
For purposes of game and range management, carrying capacity is usually defined as the maximum population of a given species that can be supported indefinitely in a defined habitat without permanently impairing the productivity of that habitat. However, because of our seeming ability to increase our own carrying capacity by eliminating competing
species, by importing locally scarce resources, and through technology, this definition seems irrelevant to humans. Indeed, trade and technology are often cited as reasons for rejecting the concept of human carrying capacity out of
hand. [According to orthodox theory, free trade is invariably good, resulting in improved living standards and increased aggregate productivity and efficiency -- increased carrying capacity -- through comparative advantage.]
This is an ironic error -- shrinking carrying capacity may soon become the single most important issue confronting humanity. The reason for this becomes clearer if we define carrying capacity not as a maximum population but rather as
the maximum "load" that can safely be imposed on the environment by people. Human load is a function not only of population but also of per capita consumption and the latter is increasing even more rapidly than the former due
(ironically) to expanding trade and technology. As Catton (1986) observes: "The world is being required to accommodate not just more people, but effectively 'larger' people . . ." For example, in 1790 the estimated average daily energy consumption by Americans was 11,000 kcal. By 1980, this had increased almost twenty-fold to 210,000 kcal/day (Catton 1986). As a result of such trends, load pressure relative to carrying capacity is rising much faster than is implied by mere population increases.
The Ecological Argument
Despite our technological, economic, and cultural achievements, achieving sustainability requires that we understand human beings as ecological entities. Indeed, from a functional perspective, the relationship of humankind to the rest of the ecosphere is similar to those of millions of other species with which we share the planet. We depend for both basic needs and the production of artifacts on energy and material resources extracted from nature and all this energy/matter is eventually returned in degraded form to the ecosphere as waste. The major material difference between humans and other species is that in addition to our biological metabolism, the human enterprise is characterized by an industrial metabolism. In ecological terms, all our toys and tools (the "capital" of economists) are "the exosomatic equivalent of
organs" (Sterrer, 1993) and, like bodily organs, require continuous flows of energy and material to and from "the environment" for their production and operation. It follows that in a finite world:
* Economic assessments of the human condition should be based on, or at least informed by, ecological and biophysical analyses.
* The appropriate ecological analyses focus on the flows of available energy/matter (essergy) particularly from primary producers--green plants and other photosynthesizers -- to sequential levels of consumer organisms in ecosystems (specifically, humans and their economies) and on the return flows of degraded energy and material (wastes) back
to the ecosystem.
This approach shows that humankind, through the industrial economy, has become the dominant consumer in most of the Earth's major ecosystems. We currently "appropriate" 40% of the net product of terrestrial photosynthesis (Vitousek et al., 1986) and 25-35% of coastal shelf primary production (Pauly & Christensen, 1995), and these may be unsustainable proportions. [Global fisheries yields have fallen since 1989.] At the same time some global waste sinks seem full to overflowing.
A fundamental question for ecological economics, therefore, is whether the physical output of remaining species populations, ecosystems, and related biophysical processes (i.e., critical self-producing natural capital stocks), and the waste assimilation capacity of the ecosphere, are adequate to sustain the anticipated load of the human economy into the next century while simultaneously maintaining the general life support functions of the ecosphere.
This "fundamental question" is at the heart of ecological carrying capacity but is virtually ignored by mainstream analyses.
Approptiated Carrying Capacity and Ecological Footprints
We can now redefine human carrying capacity as the maximum rates of resource harvesting and waste generation (the maximum load) that can be sustained indefinitely without progressively impairing the productivity and functional integrity of relevant ecosystems wherever the latter may be located. The size of the corresponding population would be a function of technological sophistication and mean per capita material standards (Rees, 1988). This definition reminds us
that regardless of the state of technology, humankind depends on a variety of ecological goods and services provided by nature and that for sustainability, these must be available in increasing quantities from somewhere on the planet as
population and mean per capita resource consumption increase (see also Overby, 1985).
Now, as noted earlier, a fundamental question for ecological economics is whether supplies of natural capital will be adequate to meet anticipated demand into the next century. Inverting the standard carrying capacity ratio suggests a
powerful way to address this critical issue. Rather than asking what population a particular region can support sustainably, the carrying capacity question becomes:
How large an area of productive land is needed to sustain a defined population indefinitely, wherever on Earth that land is located? (Rees, 1992; Rees & Wackernagel, 1994; Wackernagel & Rees, 1995). Since many forms of natural income (resource and service flows) are produced by terrestrial ecosystems and associated water bodies, it should be
possible to estimate the area of land/water required to produce sustainably the quantity of any resource or ecological service used by a defined population at a given level of technology. The sum of such calculations for all significant
categories of consumption would give us a conservative area-based estimate of the natural capital requirements for that population.
Directions
So how can you personally have an impact on the sustainability of the environment? The first thing you should do is to recognize how you contribute directly or indirectly to the problem. Then you need to figure out how you can reduce your impact and increase your green practices.
You can do all of this by knowing your ecologocial or carbon footprint.
What is your ecological footprint?
Your ecological footprint is the total amount of greenhouse gases produced by human activities. It is measured in units of carbon dioxide.
Your task will be to better understand the Ecological Footprint and learn how you can reduce your personal footprint.
Go to the Global Footprint Network
Go to the top of the page and find the section called Footprint Basics. Find "Overview" in the drop down screen. Answer the following questions in your notebook or a word document
"Describe basically what an ecological footprint is and what it measures".
From the menu on the left, find the "World Footprint link". Answer the following questions in your notebook.1) Describe the growth of the world ecological footprint from 1960-2007; 2) Describe and explain the two potential ecological footprint models for the year 2050; 3) What is overshoot?
Go back to the Overview. On the menu find "Footprint For Nations". From the "Country Trends" box, select "United State of America". Answer the following questions in your notebook. 1) What year was the United States’ ecological footprint and biocapacity equal; 2) Describe the growth trends of the ecological footprint and biocapacity; 3) What are the three major factors that account for an individual’s ecological footprint (in hectares per person)?; 4)List the ecological footprint for a U.S. citizen in the following years- 1961, 1973, 1985, 2001, 2005.
Go back to the drop down menu of "Footprint For Nations" and select "Japan" . Answer the following questions in your notebook.
1) How does Japan’s ecological footprint compare to its biocapacity overall; 2) When will Japan’s biocapacity and ecological footprint equalize?; 3) How does a Japanese citizen’s ecological footprint compare to someone from the U.S. in the year 2005?
Go back to the drop down menu of "Footprint For Nations" and select "Chile". Complete the following questions in your notebook.
1) How does Chile’s biocapacity compare to its ecological footprint overall?; 2) What to you think this says about Chile’s long term sustainability compared to the U.S. or Japan?; 3) Estimate the average ecological footprint (in hectares per person) for a resident of Chile from 1961 to 2005.
Go back to the "Overview". Now go to the left hand links and find Carbon footprint. Answer the following questions in your notebook.
1) How much of the ecological footprint is represented by the "Carbon Footprint"?; 2) Typically the carbon footprint refers to emissions. How is the carbon footprint here utilized in a different way as incorporated into the model?; 3) How do carbon emissions exemplify the "tragedy of the commons"?
Go back to the "Overview". Now find the Personal Footprint link and complete the Quiz. Answer the following questions in your notebook.
1) What was your ecological footprint according to the model in terms of the number of Earth’s necessary to sustain you lifestyle? Did this surprise you? Why or why not?; 2)How many global acres of Earth’s productive area are required? Tons of Carbon Dioxide?; 3) List the percentage breakdown for each of the five categories in the pie chart for your ecological footprint.
Click on the explore scenarios button on your Footprint page….Click on at least two of the "What if" selections and then click "OK". Describe the two actions you chose, and the effect on your ecological footprint. Record this information in your notebook.
Click "OK" one more time, and when prompted click on the "Save Footprint" button….you’ll need to enter a valid email address and pick a password. Now you can access your footprint any time.
Congratulations on a job well done
