Watch how you step:  A Case for Understanding the Impacts of Your Personal Consumption on the Environment

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Image credit: Phil Testemale    

 

I. INTRODUCTION & BACKGROUND

On October 12, 1999, Secretary-General of the United Nations, Kofi Annan, welcomed Adnan Nevic of Sarajevo, Kosovo, into the world, marking the symbolic birth of the 6 billionth living human.  The event rejuvenated longstanding debate about how many people the earth can support before exhausting the supply of natural resources and a clean environment.  Most current estimates project a human carrying capacity, or the number of people that the Earth can support, at around 12 billion, occurring sometime within the next century (Cohen 1995).

The difficulty of determining the uppermost limit of human population is that the human carrying capacity changes through time and will likely rise to some extent with increasing population.  Former President George H.W. Bush argued that "Every human being represents hands to work an not just another mouth to feed."  This suggests that more people can acquire more resources to sustain larger populations, such as building irrigation canals to grow more food or building more housing.  More people may lead to greater ingenuity and technical innovation, such as medical advances and genetically engineered crops.  However, others have pointed out that this view does not specify the cultural, environmental, and economic resources available to make additional hands productive and, therefore, does not specify by how much the additional hands can increase human carrying capacity (Cohen 1995).  For example, there is no advantage to more people in drought-stricken countries where irrigation canals are useless.  There is no advantage to more people if raw materials, such as lumber, are not available to build homes. The advantage of additional scientists may be limited if research funding declines. 

In addition, potential limits to human population size depends critically on the relative balance between the rate of consumption of natural resources and the production of waste versus the rate at which natural resources and services are provided by the planet.  Joel Cohen of Rockefeller University argues that "To believe that no ceiling to population size or carrying capacity is imminent entails believing that nothing in the near future will stop people from increasing Earth's ability to satisfy their wants by more than, or at least as much as, they consume."  Cohen emphasizes this point poignantly: "How many people the earth supports depends on how many people will wear cotton and how many polyester; on how many will eat meat and how many bean sprouts; on how many will want parks and how many will want parking lots.  These choices will change in time and so will the number of people the Earth can support."  Thus, not only does human suatainability on Earth depend on population size, it also depends on rates of material consumption and waste production by the population. 

Although human population growth rates are often highest in developing nations, income and material consumption is often more than an order of magnitude greater in wealthy industrialized nations, such as the United States, Japan, Canada, France, Germany, and England (Table 1).

Table 1. Population growth rates and doubling times of selected countries for year 2001.
Data Sources:

Country
Continent/Region
Annual Population Increase (%)
Population Doubling Time (yr)
Per-capita purchasing power (1999 $)
Palestinian Territory
Middle East
3.7 %
19
NA
Oman
Middle East
3.5 %
19
NA
Solomon Islands
Oceana
3.4 %
20
2,050
Yemen
Middle East
3.3 %
21
730
Chad
Africa
3.3 %
21
840
Maldives
Asia
3.2 %
22
4880
Liberia
Africa
3.1 %
23
NA
Demo. Rep. Congo
Africa
3.1 %
23
590
Bhutan
Asia
3.1 %
23
1,260
Gambia
Africa
3 %
23
1,550
Mali
Africa
3 %
23
740
Saudi Arabia
Middle East
2.9 %
24
11,050
Guatemala
Central America
2.9 %
24
3,630
Pakistan
Asia
2.8 %
25
1,860
Honduras
Central America
2.8 %
25
2,270
Paraguay
South America
2.7 %
26
4,380
China
Asia
0.9 %
77
3,550
United States
North America
0.6 %
116
31,910
France
Western Europe
0.4 %
174
23,020
Canada
North America
0.3 %
231
25,440
Japan
Asia
0.2 %
347
25,170
United Kingdom
Western Europe
0.1 %
693
22,220
Italy
Western Europe
0 %
--
22,000
Greece
Western Europe
0 %
--
15,800
Poland
Eastern Europe
0 %
--
8,390
Sweden
Western Europe
0 %
--
22,150
Germany
Western Europe
-0.1 %
--
23,510
Czech Republic
Eastern Europe
-0.2 %
--
12,840
Latvia
Eastern Europe
-0.6 %
--
6,220
Russia
Eastern Europe
-0.7 %
--
6,990
Ukraine
Eastern Europe
-0.7 %
--
3,360

To the extent that material consumption drives energy use, resource extraction, pollution, climate change, and landfill buildup, this means that industrialized nations, although perhaps not more populous than developing nations, have a larger per-capita impact on the environment (Brown et al. 1993, Herendeen 1998).  The United States, by virtue of its massive per-capita consumption of natural resources and energy and its generation of CO2 and waste, could be considered the most overpopulated country in the world in terms of environmental impact (Cohen 1995, Gardner and Sampat 1999).

Can the earth sustain current rates of material consumption and pollution?

Earth is strained by rapidly rising per-capita consumption, especially in industrial nations.  Modern societies are consuming more natural resources and generating more waste than at any time in human history.  For example, the average American uses 101 kilograms of materials in a given day in both direct consumption of goods and indirect consumption of materials required to make those goods (Gardner and Sampat 1999). 

Material consumption is having significant impacts on the global environment.  The global cycles of carbon and nitrogen are now dominated by human inputs, often eclipsing natural rates of movement of material by the biosphere and geosphere.  From 1860 to 1991, human population quadrupled, whereas energy consumption rose 93 fold (Cohen 1995).  Most of this energy consumption is provided by the combustion of fossil fuels, which releases greenhouse gases like carbon dioxide into the atmosphere.  In 1998, the top five industrial polluters alone (USA, China, Russia, Japan, and India) contributed more than half of global carbon emissions[1] (Marland et al 2001).  The anthropogenic rise in carbon dioxide is occurring at a rate hundreds of times faster that any change seen during the last ice age over the past 1.6 million years.  By the end of the 21st century, atmosphereic carbon dioxide levels will reach the highest levels seen in the last 30 million years (Pearson and Palmer 2000).  Stanford ecologist, Peter Vitousek, determined that humans co-opt approximately 40% of total plant productivity on Earth (Vitousek 1986).  Moreover, the exponential growth of nitrogen fertilizers following WWII now rivals nitrogen fixation by the biosphere in terms of the amount of new nitrogen introduced into the environment each year, leading to chronic problems of acid rain, eutrophication, and the destruction of stratospheric ozone (Vitousek 1994).  Lastly, wood comprises one fraction of these materials, and current logging rates in tropical countries to supply this demand is leading to record rates of rainforest destruction (Laurance 1997, Laurance 2000).  Given that the tropics may support 50-80% of the world's biodiversity, destruction of this habitat may be driving 8-11 species extinct per day (Wilson 1992).

Clearly, consumption in the industrialized world is rapidly converting natural capital to material goods, resulting in the decline in primary forests, biodiversity, clean air and water, ozone and the buildup of atmospheric pollution and solid-waste landfills.  At the global level, steady changes in these indicators of environmental health all suggest that rates of material consumption are not sustainable in the long term

Can we measure sustainability? The big glass dome analogy and the ecological footprint

Instead of the difficult task of estimating the human carrying capacity (number of people per total land area of Earth), Mathis Wackernagel and colleagues at Redefining Progress[2] developed the "ecological footprint" to quantify humanity's long-term impact on the global environment (Wackernagel and Rees 1996). The ecological footprint represents the inverse of carrying capacity because it quantifies the amount of land area that is required to sustain the lifestyle of a population of any size--an individual, household, community, city, country, or world. For example, consider the ecological footprint of one human: Given Earth's 8.9 billion hectares[3] of productive land and its 6 billion human inhabitants, the average ecological footprint should be about 1.5 hectares per person if we assume that land use should be equitably distributed among all of the planet's citicens. This per-capita footprint provides an unambiguous benchmark with which to assess the long-term sustainability of population growth and material consumption.  Individuall footprints below 1.5 hectares are sustainable whereas footprints above 1.5 hectares are not. Footprint calculations by Wackernagel and Rees (1996) suggest that the individuals in industrialized countries often have footprints as large as 4-10 hectares.

Wackernagel and Rees (1996) posed the following thought experiment to illustrate the concept of sustainability and the ecological footprint.  Imagine you could cover your town with a big glass dome that sealed off the area of the town and its immediate atmosphere from the rest of Earth.  The question of sustainability becomes this:  How large does the dome have to be and what sorts of land use types need to be included to ensure the survival of all inhabitants?  The more your town is comprised of industrial capital, such as asphalt, buildings, and vehicles, the more difficult it becomes to sustain life because of the lack of natural capital, such as land to grow food and plants to provide life supporting oxygen and remove life-threatening carbon dioxide.  It is clear from this example that every urban center is unsustainable, as indicated by huge influxes of energy, water, food, and air from outside and exports of solid and gaseous waste.  Sealing off an urban center under a glass dome would be fatal for its inhabitants.  It is clear that the ecological footprint of cities is vastly larger than the geographic area in which they lie (Wackernagel and Rees 1996). In fact, Wackernagel and Rees estimated that if all global citizens aspired to the American lifestyle and attendant levels of consumption, we would require 2 additional Earths to provide enough land area to supply natural resources and to absorb industrial waste!

Understanding the interactions of population growth and material consumption presents a challenging study of the impacts of humans on the global environment and the long-term sustainability of humanity: 

These are some of the most hotly debated environmental questions today, leading to several international conventions like the 2002 World Summit on Sustainable Development (WSSD) in Johannesburg, South Africa.


[1] http://cdiac.esd.ornl.gov/trends/emis/graphics/top20_1998.gif
[2] http://www.rprogress.org/
[3] A hectare is an area equal to a 100-m ´ 100-m square.

II. THE ISSUE

To what extent do our lifestyles contribute to environmental impacts and the number of people the Earth can support?  How can the concept of the ecological footprint be used to measure the impacts of our personal consumption on the environment?  Is your lifestyle sustainable?

In this case, you will have the opportunity to calculate your ecological footprint based on your own consumption of resources.  You will be able to judge whether your lifestyle is sustainable relative to the global benchmark of 1.5 hectares per person.

III. CALCULATING YOUR FOOTPRINT

In this case, you will record your consumption of energy and materials in each of the following six categories:

The following table provides a guide for the specific items and quantities you should monitor over the time span of a month.  Once you have tallied your monthly consumption of these items, use the footprint spreadsheet to directly convert the amount of goods and services you consume and waste you produce into an area of land needed to support them. 

Downloading the Miscosoft Excel spreadsheet

Using the Spreadsheet

You will use a spreadsheet developed by Mathis Wackernagel and colleagues at Redefining Progress (Wackernagel et al. 2000).  This following description provides an overview of how the spreadsheet works: 

How does the ecological footprint work?  Understanding the spreadsheet calculations

Using the spreadsheet to calculate an ecological footprint does not require a detailed understanding of how the spreadsheet converts material and energy consumption and waste into land area.  However, examining the relationship between land area and material and energy consumption provides a rich understanding of how humanity impacts the environment--impacts that we may not commonly think about.

The following links describe these calculations in depth, showing the innovative approaches that Wackernagel and colleagues developed to assess individual sustainability.

Specific Notes about the Spreadsheet Calculations

The following section describes how specific land use types are important for producing the materials and absorbing waste in the spreadsheet.  As explained below, some calculations are modified from the general description presented in the Introduction to calculations page.  By clicking on the red triangles in the spreadsheet, you can show comments describing each calculation.

Other notes about the Spreadsheet Calculations

 

IV. QUESTIONS FOR FURTHER THOUGHT

1.  List the factors that contributed to your footprint, from the largest to smallest contribution, what did you find?  Are you surprised or shocked by these results?

2.  Based on your ecological footprint calculation, where might you consider your lifestyle to be sustainable?  Not sustainable?

3.  What specific actions could you take to reduce your footprint? 

4. How realistic/achievable are these reductions?  Would they force you to live a fundamentally different lifestyle?

5.  How do you feel about the fact that the average footprint of a citizen in the United States is 4-10 ha compared to the global average of 1.5 ha?  Why is this the case?  Should anything be done about it?  If so, what?

 

V. EPILOGUE

More than a decade before Wackernagel and Rees (1996) published their concept of the ecological fooprint, a company called Space Biospheres Ventures began an ambitious project -- Biosphere II --to replicate a self-sustaining biosphere like Earth's (a.k.a. Biosphere I). Research to determine what constitutes a basic life support system for humans has been common since the 1960's as part of a broad mission of space travel. A self-sustaining biosphere might enhance the durations of space flights or allow humans to colonize another planet like Mars.

Between 1984 and 1991, Biosphere II was built in Oracle, Arizona for over $200 million (Cohen and Tilman 1996) (Fig. 1). Nothing this comprehensive or complex has ever been attempted before or since.

Click on images to enlarge
Fig. 1 Biosphere II Fig. 2. Ecosystems in Biosphere II Fig. 3. Picture of the ocean ecosystem
photos courtesy of Biosphere II

The purpose of the center was not just a building where people could attempt to live sustainably--it was much bolder. Biosphere II was a glass chamber sealed off from the atmosphere and containing living ecosystems, including a tropical rainforest, ocean, savannah, desert, marsh, and agricultural landscape (Fig. 2). The original footprint enclosed 13,000m2 of land and a total volume of 204,000m3 (Cohen and Tilman 1996).

The original test of Biosphere II occurred in 1991 to determine if these ecosystems could support the lives of eight people in perpituity. Their only source of food was what they could grow in the agricultural sector. Their only source of oxygen was from plants and algae in the terrestrial and oceanic ecosystems. In this respect, Biosphere II is a living experiment of Wackernagel and Rees' big glass dome analogy. Eight people were sealed in the dome in 1991. To date, this has been humanity's best test to see if we understand the ecology of the biosphere well enough to fabricate our own life support system.

Biosphere II failed to sustain these eight scientists for even two years. Before two years had elapsed, the oxygen concentration fell to 13%--roughly equivalent to that at the peak of Mt. Everest. Atmospheric CO2 rose to about 1700 ppm, similar to a level last seen at the time of the dinosaur extinction 65 million years ago (Pearson and Palmer 2000). Ants from the tropical forest took over the insect world, eating the eggs of other species and driving pollinating species extinct, forcing the researchers to pollinate plants themselves. By 1993, fresh air was pumped into Biosphere II, the researchers were able to leave the system, and the test was over.

Why did Biosphere II fail? Much of the answer lies in the fact that researchers did not correctly judge the quantity of different ecosystems that were needed to sustain human life, and they did not anticipate how the entire system would adjust after it was sealed off. Specifically, too much soil was added in the tropical rainforest biome. The microbes in the soil, under the warm conditions in Biosphere II, decomposed the soil carbon, releasing CO2 to the atmosphere and consuming O2. This, in part, drove down the quantity of breathable air and created a greenhouse effect with the high CO2. Another factor that contributed to the decline in oxygen was the cement materials use to construct the foundation. Other surprises included the near complete takever of the animal kingdom by ants, which eliminated valuable ecosystem services like pollination, without which the humans had to reproduce by hand.

Biosphere II is a valuable lesson about sustainability. Even in our best attempt to sustain the lives of just eight people, we could not develop an artificial biosphere that was sufficient. Loss of ecosystem services could prove to be costly because they are invaluble to humanity (Costanza et al. 1997). Consider what it would take for a glass dome over your house, town, city, or country to perform any better.

 

VI. LITERATURE CITED


Image Credits: Phil Testemale, Biosphere II
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