Ecological Footprint
M Wackernagel and J Kitzes, Global Footprint Network, Oakland, CA, USA
Published by Elsevier B.V.
Introduction
Metabolism: An Ecological Model of Society
Fundamental Assumptions
Ecological Footprint and Biocapacity Accounting
Methodology
Key Global and Regional Results
The Footprint of Consumption Activities
Continued Indicator Development
Further Reading
Introduction
Ecosystems provide many critical services to human
society, including both the direct provision of goods,
such as food and fiber products, as well as less-visible
services, such as water filtration and climate stabilization.
The availability of these ecosystem services depends closely
on the functioning of biological capital. Broadly
defined, biological capital consists of all of the ecosystems
and various components of the biosphere that directly or
indirectly provide goods and services. Careful management
of this capital is central to maintaining not only the
health of the natural environment but also human wellbeing
into the future.
Managing biological capital, however, requires tools
that are able to track its availability and its use. The
Ecological Footprint is an accounting tool that calculates
human demand on the biosphere, and compare this to the
planet’s ability to meet these demands. By answering the
specific research question, ‘‘how much of the Earth’s
regenerative capacity is occupied by human activities?,’’
footprint analysis helps governments, businesses, and
individuals track the use and availability of biological
capital over time. Similar to financial balance sheets, the
resulting ecological accounts can be used as a quantitative
input into decision making at all levels.
Metabolism: An Ecological Model of
Society
The Ecological Footprint applies principles of ecology to
human society to create a framework for mapping
society’s metabolism. In a generalized ecosystem model,
primary producers fix energy from sunlight through
photosynthesis. This energy is then available for consumers,
who use this primary production for growth and
maintenance activities. All material ingested by consumers,
however, eventually returns to the biosphere as
waste products, where it is broken down and recycled
back into the raw materials for primary production.
This model, where every input eventually turns into
waste, holds for any organism that exists in a natural
environment, including human society. The human economy
takes high-quality matter and energy as inputs from
the environment and returns these in degraded form as
material waste and heat. Societies consume resources in
order to maintain themselves. Between resource intake
and waste discharge, matter accumulates in these systems,
leading to increased body mass in the case of animals, or
an accumulation of material stocks in societies.
From a human perspective, the ability of the biosphere
to absorb wastes and regenerate resources is known as the
regenerative capacity of the planet. Although the Earth’s
regenerative capacity is robust, it can be eroded in three
significant ways, according to The Natural Step:
1. Natural cycles can be overwhelmed by harvesting
renewably generated resources, such as trees or fish, faster
than they can be replenished. Direct physical interference,
such as the paving over of green surfaces or farming
practices that cause soil erosion, can also damage the
underlying capital that creates these resources, further
reducing the Earth’s total regenerative capacity.
2. Substances produced by society that are persistent
and do not readily break down, and which ecosystems
have not developed abilities to assimilate,
can compromise regenerative capacity as they accumulate
in the biosphere. Examples include synthetic
chemicals such as DDT and PCBs. Many of these manmade
substances have no natural analogs, and the biosphere
as a whole has not evolved efficient means to break
down and re-assimilate these products on human
timescales.
3. Substances normally buried deep with the Earth’s
crust can be extracted, refined, and introduced into the
biosphere at quantities that ecosystems are not able to
assimilate. Examples include heavy metals, radioactive
elements, minerals, and mined carbon. Because there are
few natural cycles that can return these substances to the
crust within human time spans, these substances systematically
accumulate in the biosphere.
Human Ecology | Ecological Footprint 1031
The fundamental insight of the metabolism model is that,
in the long term, the biosphere must be able to turn wastes
back into resources faster than the human society turns
the resources into waste. If the extraction of resources
becomes too large, or if nature’s regenerative capacity is
compromised, biological capital will be systematically
degraded and wastes will accumulate.
While in the past, most ‘environmental’ problems arose
from poor management of some local aspects of society’s
metabolism, such as careless waste disposal, smokestacks,
or overuse of a river basin, now the very size of society’s
global metabolism that has become the overarching concern.
While local overuse of the biosphere has a long
history (e.g., overfishing, deforestation, soil erosion), the
global human economy has now become so large, relative
to the regenerative capacity of planet Earth, that it is now
for the first time in human history confronting global
limits.
Fundamental Assumptions
In order to provide a quantitative answer to the research
question of how much regenerative capacity is required to
maintain a given resource flow through human society,
Ecological Footprint analysis uses a methodology
grounded on six basic assumptions:
1. The annual amounts of resources consumed and wastes
generated by countries are tracked by national and international
organizations. Most countries have extensive annual statistics
documenting their resource use, particularly in the
areas of energy, forest products and agricultural products.
United Nations agencies, like the Food and Agriculture
Organization (FAO), compile many of these national statistics
in a consistent format.
2. The quantity of biological resources appropriated for
human use is directly related to the amount of bioproductive
land area necessary for regeneration and the assimilation of
waste. Bioproductive processes are associated with surfaces
that capture sunlight for photosynthesis. Even
three-dimensional processes that represent layers of
such surfaces, as in aquatic ecosystems or rainforests,
can be mapped on the two-dimensional area.
3. By weighting each area in proportion to its usable biomass
productivity (i.e., its potential annual production of usable biomass),
the different areas can be expressed in terms of a
standardized average productive hectare. This unit is referred
to as a global hectare, a hectare of surface area with
world-average useful biological productivity.
4. The overall demand in global hectares can be aggregated by
adding all mutually exclusive resource-providing and wasteassimilating
areas required to support the demand.
5. Aggregate human demand (Ecological Footprint)and nature’s
supply (biocapacity) can be directly compared to each other.
By using the standardized unit of a global hectare,
demand and supply can be compared, as can different
components of demand and supply.
6. Area demanded can exceed area supplied. A footprint
greater than available biocapacity at any given scale indicates
that demand exceeds the regenerative capacity of
existing biological capital. This condition, known as
‘overshoot’, is possible in the short term, as resources
can be harvested faster than they regenerate (e.g., deforestation)
and wastes can accumulate (e.g., carbon dioxide
in the atmosphere). In the long term, however, such overshoot
leads to increasing risks of ecological degradation or
collapse.
Ecological Footprint and Biocapacity
Accounting
Ecological Footprint analysis examines the size of
society’s metabolism with a specific research question:
how much of the regenerative capacity of the biosphere
is being occupied by human activities? To answer this
question, footprint analysis measures how much biologically
productive land and water area an individual, a city,
a country, a region, or humanity uses to produce the
resources it consumes and to absorb the waste it generates,
using prevailing technology and resource
management schemes.
This demand can be compared with supply, or biocapacity,
the total available biologically productive surface
of the planet. The common unit used for this analysis, as
the term ‘footprint’ suggests, is a global hectare, one
hectare of land or sea with world-average biological
productivity.
Calculating Demand: Footprint
At present, human demands on ecosystems, a population’s
footprint, are translated into demands for six major land
types – cropland, grazing land, fishing grounds, forest,
built-up land, and ‘carbon land’ (Table 1). The first four
Table 1 Major land types in Ecological Footprint and
biocapacity accounting. The biocapacity associated with
emissions of carbon dioxide is represented by forest land
Ecological Footprint Biocapacity
Cropland Cropland
Grazing land Grazing area
Fishing grounds Fishing grounds
Forest Forest
Built-up land Built-up land
‘Carbon land’ NA
From Global Footprint Network (2005) National Footprint Accounts,
2005 edition. Available at http://www.footprintnetwork.org.
1032 Human Ecology | Ecological Footprint
of these land types produce food, fiber, and timber products
for human consumption. These products may be
consumed directly or processed further before final consumption.
Regardless of the forms they eventually take
within society, however, all products produced from these
four land types can be translated, through the use of yields
(annual tonnes per hectare) and conversion factors
(tonnes of processed product per tonnes of raw material),
back into the amount of area required to produce the
products. This land and water area can be located anywhere
on the planet.
The fifth land type, built-up land, represents the area
required for the physical infrastructure associated with
human society, such as cities and roads. The sixth land
type, carbon land, represents the amount of biologically
productive space required to absorb one of the human
economy’s most significant waste products: carbon dioxide.
This footprint is currently calculated as the amount of
forested area required to sequester a given amount of
carbon dioxide, effectively removing it from the atmosphere,
after accounting for absorption by the oceans.
This approach of translating fossil fuel use into bioproductive
area does not suggest that afforestation or
other types of biological sequestration are the solution
to reducing atmospheric carbon dioxide concentrations.
These measures do show, however, how much larger the
biosphere would need to be to stabilize carbon dioxide
concentrations in the atmosphere without further human
intervention. The 2005 Edition of the National Footprint
Accounts, for example, calculates that in 2002 the release
of one tonne of carbon dioxide per year has a footprint of
approximately 0.27 global hectares. Other human-supported
methods exist for sequestering carbon dioxide,
and the use of these technologies will be reflected in a
decrease in the energy footprint as they are brought on
line. Similarly, the introduction of renewable energy
technologies with lower carbon intensities will also lead
to a reduced carbon footprint.
Calculating Supply: Biocapacity
Human demand, or footprint, can be compared to the
total availability of biologically productive land and sea,
or biocapacity. Biocapacity is currently measured in five
major land types (Table 1), analogous to the six land
types of footprint with the exception of ‘carbon land’
(the regenerative capacity available for sequestering carbon
dioxide emissions is included in the other major land
types).
Globally, footprint analysis identifies, for 2002,
approximately 11.2 billion hectares of biologically productive
land and sea that can provide economically useful
concentrations of renewable resources. These 11.2 billion
hectares cover just under one quarter of the planet’s
surface and include 1.5 billion hectares of cropland, 3.5
billion hectares of grazing land, 3.6 billion hectares of
forest, 2.3 billion hectares of marine and inland fisheries,
and 0.2 billion hectares of built-up land.
These areas concentrate the bulk of the biosphere’s
regenerative capacity. There are not yet concrete estimates
of precisely how much of the total usable annual
biomass generation or net primary production is concentrated
on these 11.2 billion hectares, but the number is
likely not lower than 80% or possibly 90%. While the
remaining areas of the planet are also biologically active,
such as the deep oceans or deserts, their renewable
resources are not concentrated enough to be a significant
addition to the overall biocapacity.
Many materials and pollutants place demands on the
biosphere primarily by reducing the ability of ecosystems
to provide goods and services, which leads to a loss in
biocapacity. Toxics, heavy metals, and other persistent
pollutants fall into this category. The amount of bioproductive
area required to mine mercury, for example, is
vanishingly small compared to the extent of the ecosystems
that this metal affects. Similarly, the area required to
absorb this product is an undefined quantity, as ecosystems
do not have a well-defined or understood ability to
assimilate this metal naturally. As a result, the impacts of
mercury, as well as other toxics, do not appear primarily
in the material’s footprint but rather in the widespread
loss of biocapacity that it can cause when released widely
into the environment.
The Common Unit: Global Hectares
Given the widely varying scope of human demands, and
the wide variety of ecosystems available on the planet,
any aggregate analysis or indicator requires a common
metric for comparison. Ecological Footprint accounts
compare different types of footprints to each other and
to available biocapacity using a global hectare, defined as
a hectare with world-average ecological productivity of
the 11.2 billion bioproductive hectares on Earth.
In the context of global hectares, biological productivity
does not refer to a rate of biomass production, such as
net primary production (NPP). Rather, productivity is the
potential to achieve maximum yields of products considered
useful for human purposes. As a result, one hectare of
highly productive land (e.g., cropland) is equal to more
global hectares than one hectare of less productive land
(e.g., pasture). Global hectares are normalized so that the
number of actual hectares of biologically productive land
and sea on the planet is equal to the total worldwide
budget of global hectares in any given year.
What products are useful is defined in any year by the
types of products that are actually extracted from global
ecosystems. Useful yields, and hence total biocapacity,
Human Ecology | Ecological Footprint 1033
will increase if largely unharvested ecosystem products
(e.g., tree bark) are extracted on a large scale in the future.
Methodology
Data Sources
The most robust Ecological Footprint accounts exist at
the national and international scales. Although subnational
footprint calculations are both possible and
common, because of limitations on the availability and
accuracy of data sources, the quality of subnational footprint
calculations can be more variable. The international
community of footprint practitioners is currently in the
process of developing standards and certification procedures
for subnational footprint applications.
The National Footprint Accounts are currently maintained
by Global Footprint Network, a nonprofit
organization headquartered in Oakland, California, and
its over 65 partner organizations throughout the world.
This high-level analysis relies heavily on data published
by the FAO, the United Nations Statistics Division, the
Intergovernmental Panel on Climate Change (IPCC),
and the International Energy Agency (IEA). Other data
sources, including meta-analyses, scientific publications,
and thematic collections, are used to fill in the gaps
between these international sources.
Yield Factors and Equivalence Factors
Two conversion factors, yield factors and equivalence
factors, are used in calculations of footprint and
biocapacity.
Yield factors are calculated as the ratio of national,
country-specific yields for a given land type to the average
world yield for that same land type. This ratio
describes the extent to which a biologically productive
area in a given country is more (or less) productive than
the global average of the same land type. Differences in
national and global yields can be due to a wide variety of
factors, including variation in climate, soil conditions,
available technology, and management regimes. Yield
factors are specific to individual land types, countries,
and years.
Equivalence factors relate the average productivity of
a given land type to the world-average productivity of all
biologically productive land types. Cropland, for example,
has a higher productivity than world average land.
Grazing land is, on average, less productive than the
average of all land types. Equivalence factors are currently
calculated using Global Agro-Ecological Zones
(GAEZ) data, which provide a spatial model of potential
agricultural yields. The equivalence factor for a land type
depends on its level of potential agricultural productivity
relative to other land types.
Calculating Footprint and Biocapacity
The general formula for calculating the Ecological
Footprint associated with the consumption of a quantity
of product is given as
EF ¼ ðM=NYÞ Â YF  EQF ½1Š
where EF is the Ecological Footprint of a given product
flow (in global hectares), M is the mass of the product flow
(in tonnes per year), NY is the national yield of the
country in which that product was produced (in annual
tonnes per hectare per year), YF is a yield factor calculated
as the ratio of national yields to world yields for a
given product, and EQF is an equivalence factor reflecting
the relative productivity of a given land type
compared to world-average productivity.
This formula can be applied directly to all products
harvested directly from the first four major productive
land types: cropland, grazing land, fishing ground, and
forest land. The footprints of secondary products (e.g.,
flour) that are created from primary products (e.g.,
wheat) are calculated by converting them back into primary-product
equivalents.
The footprint of built-up land is calculated by using
the physical extent of the area occupied in built area (in
hectares) instead of the product of mass (M) and national
yield (NY). Yield and equivalence factors for cropland are
applied, reflecting the assumption that most built land
occupies former cropland, unless more accurate data are
available. The footprint of ‘carbon land’ is calculated
using the total mass of carbon dioxide emissions released
from a given activity and the world-average sequestration
rate of forested land in place of the ratio of national yield
(NY) and yield factor (YF).
To calculate the footprint of a nation, the footprint of
all products consumed within that country is calculated
using the formula above and then summed. The global
Ecological Footprint is calculated as the sum of all
national footprints.
The biocapacity associated with a given productive
land or sea area is calculated in a similar fashion:
BC ¼ A  YF  EQF ½2Š
where BC is the useful biocapacity of a given area (in
global hectares), A is physical extent of the area under
analysis (in country-specific hectares), YF is a yield factor
for that country and land type, and EQF is an equivalence
factor for that land type. Note that this formula is identical
to that for Ecological Footprint, except here area
substitutes for the ratio of mass and national yield. This
formula can be applied equally to all five major productive
land types on the planet: crop land, grazing land,
fishing grounds, forest land, and built-up land.
1034 Human Ecology | Ecological Footprint
Key Global and Regional Results
At the largest scales, global Ecological Footprint analysis
shows that the total human footprint, or demand on
ecosystems, exceeds the planet’s available biocapacity,
or its ability to supply resources and waste sinks.
Figure 1 shows that this condition of overshoot has
existed since the mid-1980s. The most significant growth
in Ecological Footprint over this time period has been a
result of an increase in the productive land area required
to meet human demands for fossil fuel energy. This
energy land footprint made up nearly 50% of the total
Ecological Footprint at a global level in 2002. The growth
in available biocapacity over time largely reflects
increases in the productivity of cropland. These increases
also led, however, to increases in application of fertilizers
and pesticides, the creation of which contributed to the
rapidly growing Ecological Footprint over this same time
period.
These consistently growing global trends, however,
mask significant regional variation (Figure 2). In 2002,
the per person Ecological Footprint of North America
and Western Europe was more than double the biological
capacity available within those regions. If everyone in the
world lived with a level of ecological demand equal to the
typical North American or western European, humanity
would require the equivalent production of three to five
planets. Other regions, such as Asia Pacific, have an average
level of ecological demand that could be extended
globally without causing overshoot.
Levels of demand also vary significantly between
high-, middle-, and low-income countries (Figure 3). In
2002, high-income countries had an average Ecological
Footprint of 6.4 global hectares, compared to 1.8 global
hectares for middle-income nations and 0.8 global hectares
for low-income nations. Over the past 40 years, consumption
of ecological resources, per capita, has increased by
nearly 90% in high-income countries but fallen by 15% in
low-income countries.
More detailed national-level footprint results are published
in annual editions by Global Footprint Network. A
wide range of subnational footprint assessments have also
been completed by organizations located throughout
the world. Links to these data sets and reports are available
on Global Footprint Network’s website (http://
www.footprintnetwork.org).
The Footprint of Consumption Activities
While the methods and national analysis presented above
provide information on the Ecological Footprint and biocapacity
of different land types, they do not indicate
which types of consumption are responsible for placing
these demands. The provision of food products, for
0
2
4
6
8
10
12
14
16
1961 1971 1981 1991 2001
2002globalhectares
(billions)
Figure 1 Global Ecological Footprint and biocapacity, 1961–
2002. Data in units of 2002 global hectares, hectares with
equivalent biological productivity to a world-average
bioproductive hectares in the year 2002. From Global Footprint
Network (2005). National Footprint Accounts, 2005 edition.
Available at http://www.footprintnetwork.org.
0
1
2
3
4
5
6
7
1961 1971 1981 1991 2001
Globalhectaresperperson
High income
Middle income
Low income
Figure 3 Ecological Footprint and biocapacity by national
income grouping, 1961–2002. Dotted lines indicate
discontinuities due to lack of data. From Global Footprint
Network (2005). National Footprint Accounts, 2005 edition.
Available at http://www.footprintnetwork.org.
0
2
4
6
8
10
Globalhectaresperperson
North America
Western Europe
Central/eastern Europe
Middle East and Central Asia
Latin America
Asia Pacific
Africa
Figure 2 Regional Ecological Footprint and biocapacity, 2002.
From Global Footprint Network (2005). National Footprint
Accounts, 2005 edition. Available at http://
www.footprintnetwork.org.
Human Ecology | Ecological Footprint 1035
example, requires significant quantities of cropland, grazing
land, fishing grounds, and carbon land. Dividing the
Ecological Footprint into its specific consumption components
can be valuable for policy applications and
communication programs. These results are commonly
used in scenario analysis and by individuals who wish to
find ways to reduce their own personal footprints.
Various techniques, including input–output analysis
and process-based allocation, can be applied to apportion
the Ecological Footprint into consumption categories. All
of these types of analyses can generate a consumption
land-use matrix, a table that allocates the total footprint
in each of the major land types across a series of consumption
categories. The different methods employed by
practitioners around the world to create these matrices
are currently being aligned by a global Ecological
Footprint standards process.
Table 2 shows that energy land and crop land are the
land types that make the largest contribution to the average
Australian’s Ecological Footprint. By consumption
Table 2 Process-based consumption land-use matrix for Australia
‘Carbon
land’ Cropland
Grazing
land Forest
Built-up
land
Fishing
grounds
Total
(gha/cap)
Food 0.5 1.1 0.7 0.0 0.3 2.7
Plant based 0.3 0.3 0.0 0.6
Animal based 0.3 0.7 0.7 0.0 0.3 2.1
Housing 1.1 0.0 0.3 0.1 1.4
New construction 0.1 0.0 0.3 0.0 0.4
Maintenance 0.0 0.0 0.0 0.1 0.1
Residential energy use 0.9 0.9
Electricity 0.8 0.8
Natural gas 0.1 0.1
Fuelwood 0.1 0.1
Fuel oil, kerosene, LPG,
coal
0.0 0.0
Mobility 0.7 0.0 0.1 0.8
Passenger cars and trucks 0.5 0.0 0.1 0.6
Motorcycles 0.0 0.0 0.0 0.0
Buses 0.0 0.0 0.0 0.0
Passenger raif transport 0.0 0.0 0.0 0.0
Passenger air transport 0.1 0.0 0.0 0.1
Passenger boats
Goods 1.4 0.0 0.0 0.4 0.0 1.9
Appliances (not including
operation energy)
0.0 0.0 0.0 0.0
Furnishing 0.0 0.0 0.0 0.0 0.0 0.1
Computers and electrical
equipment (not inclu.
0.0 0.0 0.0 0.0
Clothing and shoes 0.0 0.0 0.0 0.0 0.0 0.1
Cleaning products 0.0 0.0 0.0 0.1
Paper products 0.1 0.2 0.0 0.3
Tobacco 0.0 0.0 0.0 0.0 0.0
Other misc. goods 1.2 0.0 0.1 0.0 1.3
Services 0.7 0.0 0.1 0.0 0.9
Water and sewage 0.0 0.0 0.0 0.0
Telephone and cable service 0.0 0.0 0.0 0.0
Solid waste 0.0 0.0 0.0 0.0
Financial and legal 0.0 0.0 0.0 0.1
Medical 0.2 0.0 0.0 0.0 0.2
Real estate and rental lodging 0.1 0.0 0.0 0.0 0.1
Entertainment 0.0 0.0 0.0 0.1
Government 0.1 0.0 0.0 0.0 0.2
Nonmilitary, nonroad 0.1 0.0 0.0 0.0 0.1
Military 0.1 0.0 0.0 0.0 0.1
Other misc. services 0.1 0.0 0.0 0.0 0.2
0.0 0.0 0.0
Total (gha/cap) 4.4 1.1 0.8 0.8 0.3 0.3 7.7
gha/cap, global hectares per capita.
From Global footprint Network and the University of Sydney, 2001 data.
1036 Human Ecology | Ecological Footprint
category, food and goods are the most significant. The
finer level of detail in tables such as these can be used to
suggest scenarios for policymaking as well as possibilities
for individual action. Eliminating animal-based food and
doubling plant-based food consumption, for example,
could reduce the Ecological Footprint of the average
Australian by 20% each year.
Continued Indicator Development
Continued development of the Ecological Footprint
methodology and calculations is stewarded by Global
Footprint Network and its over 65 international partners.
Ongoing initiatives include maintenance and updates to
the National Footprint Accounts, extensions of Ecological
Footprint accounting techniques, and the creation of standards
for subnational footprint applications and projects.
More information can be found on Global Footprint
Network’s website at http://www.footprintnetwork.org.
See also: Climate Change 3: History and Current State;
Coevolution of the Biosphere and Climate; Deforestation;
Ecosystem Services; Ecosystems; Global Change
Impacts on the Biosphere; Urbanization as a Global
Ecological Process.
Further Reading
Chambers N, Simmons C, and Wackernagel M (2000) Sharing Nature’s
Interest: Ecological Footprints as an Indicator for Sustainability.
London: EarthScan.
Costanza R, Ayres R, Deutsch L, et al. (2000) Forum: The dynamics of
the ecological footprint concept. Ecological Economics
32(3): 341–394.
Global Footprint Network (2005). National Footprint Accounts, 2005
edition. Available at http://www.footprintnetwork.org.
Global Footprint Network and the University of Sydney (2005) The
Ecological Footprint of Victoria: Assessing Victoria’s Demand on
Nature. Report prepared for EPA Victoria. http://
www.epa.vic.gov.au/ecologicalfootprint/default.asp (accessed Apr.
2007).
Kitzes J, Wackernagel M, Loh J, et al. (forthcoming) Shrink and share:
Humanity’s present and future Ecological Footprint. Philosophical
Transactions of the Royal Society B.
Monfreda C, Wackernagel M, and Deumling D (2004) Establishing
national natural capital accounts based on detailed ecological
footprint and biological capacity accounts. Land Use Policy
21: 231–246.
Rees WE (1992) Ecological footprints and appropriated carrying
capacity: What urban economics leaves out. Environment and
Urbanization 4: 121–130.
Wackernagel M, Kitzes J, Moran D, Goldfinger S, and Thomas M (2005)
The ecological footprint of cities and regions: Comparing resource
availability with resource demand. Environment and Urbanization
18(1): 103–112.
Wackernagel M and Rees WE (1996) Our Ecological Footprint:
Reducing Human Impact on the Earth. Gabriola Island: New Society
Publishers.
Wackernagel M, Schulz NB, Deumling D, et al. (2002) Tracking the
ecological overshoot of the human economy. Proceedings of the
National Academy of Sciences of United States of America
99(14): 9266–9271.
Wiedmann T, Minx J, Barrett J, and Wackernagel M (2006) Allocating
ecological footprints to final consumption categories with input–
output analysis. Ecological Economics 56(1): 28–48.
WWF International, Global Footprint Network, and Zoological Society of
London (2006) Living planet Report 2006. Gland, Switzerland.
http://www.panda.org/living planet.
Relevant Website
http://www.footprintnetwork.org – Global Footprint Network.
Ecological Health Indicators
J R Karr, University of Washington, Seattle, WA, USA
ª 2008 Elsevier B.V. All rights reserved.
Indicators
Environmental Change and Ecological Indicators
Integrity: The Benchmark
From Environmental to Ecological Indicators
Characteristics of Ecological Indicators
Ecological Attributes Worth Measuring
How Ecological Indicators Are Used
Further Reading
Indicators
Environmental change has always been a reality, and it is
continuous. Change on planet Earth is driven by wind and
water; geological activity; astronomical events; and the
work of microorganisms, plants, and animals. Usually,
forces with the greatest potential for cataclysmic change
are rare (such as volcanic eruptions), local (such as tornadoes
or lightning fires), or slow to play out (such as the
advance and retreat of glaciers).
Although these cataclysmic changes are important for
life on Earth, most living organisms are preoccupied more
with being keen observers, relying on multiple senses to
identify threats, such as the presence of predators or
Ecological Indicators | Ecological Health Indicators 1037