Sustainability 101:

Ecological Footprints (3)

What is Sustainability?

"Meeting the needs of the present generation without compromising the ability of future generations to meet their needs."
Gro Harlem Brundtland-1987

Brundtland Report

A few sustainability indicators:

The Natural Step

Environmental Space

Systems Models

Environmental Impact Statements

Corporate Environmental Performance

Life Cycle Analysis

Material Accounts

EMergy Analysis: Embodied energy

Why use sustainability indicators?

1) They indicate a balance between quality of life and carrying capacity.

2) Land is a finite resource. It is good to have a measure of how much is available and how much is "consumed" by human activity.

3) They allow comparisons between many different entities (countries, lifestyles, products...) in a simple way.

Natural Step Principles (worksheet):

1. Substances from the Earth's crust can not systematically increase in the biosphere.

In order to achieve this goal, fossil fuels, metals, and other minerals can not be extracted at a faster rate than they are replaced.

2. Substances produced by society can not systematically increase in the biosphere.

In order to achieve this goal, substances can not be produced at a faster rate than they are broken down in nature. This requires a greatly decreased production of naturally occurring substances that are systematically accumulating beyond natural levels, and a phase-out of persistent human-made substances not found in nature.

3. The physical basis for the productivity and diversity of nature must not be systematically deteriorated.

This means that we cannot harvest or manipulate ecosystems in such a way as to diminish their productive capacity, or threaten the natural diversity of life forms (biodiversity). This requires that we critically examine how we harvest renewable resources, and adjust our consumption and land-use practices to fall well within the regenerative capacities of ecosystems.

4. In order to meet the previous three system conditions, there must be a fair and efficient use of resources to meet human needs.

This means that basic human needs must be met with the most resource-efficient methods possible, including a just resource distribution.

 

 

 

Does I really equal PAT?

Ehrlich, Ehrlich & Holdren hypothesized that the impact of human's on the earth was equal to the product of these three factors. Argue for or against this hypothesis.

• I = Impact
• P = Population
• A = Affluence
• T = Technology

You may want to check this image and then discuss the hypothesis.

Ecological Footprint Concept:

An ecological footprint is the inverse relation of carrying capacity. The carrying capacity is defined as the number of individuals (often humans) that the resources of a habitat (often planet Earth) can support. The ecological footprint is a measure of the area of land required to sustain an individual, an activity or a group of individuals (sometimes populations of entire countries or even the entire human population).

What is an ecological footprint?

The land and water area that is required to sustain the material standard of living of a given population using existing technology.

Compute your own Ecological Footprint

What factors enter into an ecological footprint calculation?

• Bioproductive (currently used) land: land used for food and materials such as farmland, gardens, pasture and managed forest.
• Bioproductive sea: sea area used for human consumption (often limited to coastal areas)
• Energy land: an equivalent amount of land that would be required to support renewable energy instead of non-renewable energy. This is discussed in more detail below.
• Built (consumed) land: land that is used for "development" such as roads and buildings.
• Biodiversity land: Land required to support all of the non-hu,an species. What's left or what should be left.
• Nonproductive land: Land such as deserts and icecaps is subtracted from the total available land area.

How is energy land calculated?

Energy land can be calculated in numerous ways. Wackernagel & Rees (1) suggest three methods that can be used. The first method yields a slightly smaller value. The latter two methods yield identical conversion factors between energy and land. The net assumption behind these calculations is the "fuel cycle" of biomass fuels:

n CO2 + n H2O + light --> n C(H2O)

 

3 C(H2O) --> CH3CH2OH + CO2

 

CH3CH2OH + 1.5 O2 --> CO2 + H2O

Method 1: Calculating the assimilative capacity for carbon dioxide from burning fuels. Thus, an equivalent forest area required to sequester the CO2 from burning fuels would represent the footprint area. The equivalent areas for footprint calculations by this method yield 100 GJ/ha/year. Thus, a consumption rate of 100 GJ of energy in one year would require 1.0 hectare (2.5 acres).

Method 2: Calculating the amount of land area required to grow the equivalent energy of the fuel as either ethanol or methanol from biomass crops. The equivalent areas for footprint calculations by this method yield 80 GJ/ha/year. Thus, a consumption rate of 80 GJ of energy in one year would require 1.25 hectare (3.125 acres).

 

 

Method 3: Converting fossil energy use into a corresponding land area estimates the land area required to rebuild natural capital at the same rate that fossil fuel is being consumed. This is essentially the same method as Method 2, except that the fuel is not actually used, but forest is grown to replace what is used. The equivalent areas for footprint calculations by this method yield 80 GJ/ha/year. Thus, a consumption rate of 80 GJ of energy in one year would require 1.25 hectare (3.125 acres).

In this class, we will use the values suggested by Wackernagel and Rees: one hectare per 1.8 tons carbon emitted per year, which is identical with Method 1.

How is built land calculated?

Built land is calculated on a hectare per hectare basis. Thus, a house on a 0.1 ha plot would consume 0.1 ha. This is perhaps the most straightforward calculation.

How much land is required to protect biodiversity?

There is no clear answer here, but we do know that humans current appropriation of about 40% of net primary productivity (3) is taking a toll on many species, as evidenced by anomalously high extinction rates. Eugene Odum (4) suggests that 1/3 of every ecosystem type be secured for biodiversity.

Gross primary productivity (GPP): Total rate of photosynthesis in a specified area.Autotrophs (most photosynthetic plants and algae) absorb solar energy and produce organic nutrients for all organisms in a community.

Net primary productivity (NPP): The rate at which plants produce organic nutrients for heterotrophs:

Where RS is the energy used by autotrophs for respiration.

In this flow of energy diagram for the ecosystem, gross primary productivity is 10,400 kcal/m 2 /yr,of which 5,720 is used for respiration and becomes heat. Net primary productivity is 4,680 kcal/m 2 /yr,of which 3,470 (increased by an input of 40 kcal/m 2 /yr)is passed on to the grazing and detrital food webs.Less than 1% is utilized by the grazing food web,and the rest is funneled through the detrital food web. Of the 3,510 kcal/m 2 /yr, 3,380 is used for respiration and becomes heat. A total of 10 kcal/m 2 /yr is an output to other ecosystems. Notice that of the original 10,400 kcal/m 2 /yr,1,210 is stored in living plant tissue, and 120 is stored as dead remains in the soil.

The biomass or dry weight (g/m^2 )for trophic levels in a grazing food web in a bog at Silver Springs, Florida.

What is the total land available?

What forms of consumption are typically calculated?

• Food
• Housing
• Transportation
• Goods
• Waste
• Services

How big a footprint does each area account for?

Each one depends on the what is used as well as the amount used. For instance, a vegetarian diet generally has a smaller footprint for an equal number of calories consumed, but even among different vegetarian diets, there is a difference in footprints. For example, a pound of bread consumes a greater footprint than a pound of vegetables. An excellent spreadsheet that allows you to compile your footprint is available on the Sharing Nature's Interest WWW site.

Passenger Transport

Mode	Footprint (ha-years/passenger-km)
Car	0.06-0.13
Bus & Train	0.03
Air	0.06-0.09

Freight Transport

Mode	Footprint (ha-years/1000 t-km)
Train	0.01
Road	0.07
Sea	0.01
Air	0.32

Electricity

Source	Footprint (ha-years/GW-hr)
Hard coal condensing	161
Coal	198
Oil	150
Natural Gas	94
Wind	6
Photvoltaics	24
Biomass-woody	27-46
Hydro	10-75

Food

Food Type	Footprint (ha/year/tonne)
Grain	1.7-2.8
Pulses	3.6-4.4
Roots & Vegetables	0.3-0.6
Meat	6.9-14.6
Milk	1.1-1.9
Fish	4.5-6.6
Fruit	0.5-0.6

Various Materials & Waste

Material & Waste	Footprint (ha-years/tonne)
Timber	1.0-5.7
Concrete	.01
Steel	0.8-1.4
Cotton Garments	5.6-5.8
Paper (landfill)	2.8-4.0
Paper (recycle)	2.0-2.9
Glass (landfill)	1.0-1.1
Glass (recycle)	0.8-0.9
Aluminum (landfill)	9.4-17.8
Aluminum (recycle)	0.4-0.9
Plastic (landfill)	3.6-4.1
Plastic (recycle)	1.1-3.3

How big is our footprint?

How do different countries' footprints compare?

Country	Footprint (ha/capita)
World Average	2.2
U.S.	9.6
France	5.3
Brazil	3.6
China	1.4
Canada	7.2
Mexico	2.5
Russian Federation	4.6
India	1.0

Questions:

What countries have the largest and smallest ecological footprints?

How might the different footprints in Q1 relate to The Natural Step Condition 4 for sustainability?

What are the greatest contributions to your footprint?

What components of your footprint would be easiest to reduce?

References:

1) Our Ecological Footprint, Mathis Wackernagel and William Rees

 

2) Sharing Natures Interest, Nicky Chalmers, Craig Simons, Mathis Wackernagel

3) Many ideas, all diagrams and data are excerpted from: Sharing Nature's Interest, by Chambers, Simmons & Wackernagel