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What assumptions
do you make in your Footprint calculations?
Ecological Footprint calculations are based on five assumptions:
- It is possible to keep track of most of the resources
people consume and many of the wastes people generate. Much
of that information can be found in existing official statistics.
- Most of these resource consumption and waste flows can
be converted into the biologically productive area that
is required to maintain these flows.
- These different areas can be expressed in the same unit
(hectares or acres) once they are scaled proportionally
to their biomass productivity. In other words, each acre
can be translated into an equivalent area of world-average
land productivity.
- Since these areas stand for mutually exclusive uses, and
each standardized acre represents the same amount of biomass
productivity, they can be added up to a total—a total
representing humanity's demand.
- This area for total human demand can be compared to Earth's
supply of natural resources, since it is also possible to
assess the area on the planet that is biologically productive.
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What data sources
do you use to calculate the Footprint?
The analysis is primarily based on data published by United
Nations agencies and the Intergovernmental Panel on Climate
Change.
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What is the unit of measurement
for a Footprint?
The Ecological Footprint is expressed in global hectares
(gha) or acres. 1 gha = 2.47 acres.
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How do you calculate
the size of an Ecological Footprint?
Footprints are calculated using a methodology that includes
these steps:
- Identify and add up the amount of biocapacity in a country
or the world; i.e., how many hectares (or acres) of land
are dedicated to crop production, pasture land, forests,
fishing, carbon storage areas, and built space.
- Use equivalence factors to normalize all biocapacity categories
into global hectares; i.e., making crop land, grasslands,
and forest comparable using a common denominator such as
net primary productivity or agricultural potential.
- Subtract biocapacity for the needs of non-human life.
- Determine the average yield factors for a hectare of biocapacity;
e.g., how many tons of beans per hectare of crop land are
produced.
- Use the biocapacity and yield factors to measure the area
of biocapacity a population’s consumption and waste
output requires over the course of a year; e.g., one ton
of beans might require 1/2 global hectare to grow, and thus
the footprint of two tons of bean consumption is one global
hectare.
- For a country-level Footprint an additional step is taken
to add in imports and subtract exports in the final tally.
(This step is not needed for the global Footprint-biocapacity
estimates.)
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How do you
interpret the results of a Footprint calculation?
On a global level, the results are biocapacity (supply) estimates
for crop land, pasture land, forest, fisheries, and carbon
storage areas. We compare that to the footprint (demand) for
food, forest, and other resource consumption categories, as
well as carbon emissions.
The Footprint is the area of biocapacity needed to produce
what the world’s population consumes, and to absorb
(some of) the ensuing waste.
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