Ecological Footprint and the Earth’s Biocapacity
We are in the middle of an ecological overshoot situation. This is the sobering key finding of the World Wildlife Fund Living Planet Report 2012, released earlier this week.
The Living Planet Report arrived at this conclusion by calculating the discrepancy between human demands on the biosphere (ecological footprint) and the earth’s biocapacity. According to the report the world’s ecological footprint is continuing on a path of over-consumption. Statistics show that in 2008 the earth’s biocapacity was 12.0 billion gha (global hectare) while humanity’s ecological footprint was 18.2 billion gha.
“This discrepancy means that we are in an ecological overshoot situation: it is taking 1.5 years for the Earth to fully regenerate the renewable resources that people are using in a single year. Instead of living off the interest, we are eating into our natural capital.”
-WWF Living Planet Report 2012
GHA – Global Hectare
Both the Ecological Footprint and the earth’s biocapacity are expressed in units of gha or global hectare. 1 gha equals a biologically productive hectare capable of world average productivity. The ecological footprint (demand) is measured against the earth’s biocapacity (supply). In this case, humans’ demands exceed the earth’s biocapacity by over 50% in a year.
Different countries have different biocapacities, specified by two factors: the bioproductive area available in the country (agricultural land, forests, fishing grounds, etc.) and the bioproductivity per hectare. The latter is dependent on variables like weather, sustainable agricultural practices, health, etc. According to the WWF report, countries with high biocapacity per person tend to have extensive forest areas, like Bolivia and Canada.
However, even countries with low biocapacities can have high ecological footprints, like the UAE (0.6 gha biocapacity per person to 8.4 gha ecological footprint). This is due to export and use of one nation’s biocapacity to supply another nation’s needs. The Living Planet Report defines the components of the ecological footprint as:
- Carbon – the amount of forest land needed to sequester carbon emissions (not including the amount absorbed by the ocean and leads to ocean acidification)
- Cropland – the amount of productive land needed to grow crops for food, fibre, oil crops, etc.
- Forest– the amount of forest needed to supply fuel wood, pulp, and timber
- Built-up land – land occupied by manmade infrastructure
- Grazing Land – amount of land needed to raise livestock
- Fishing Grounds – estimated primary production needed to support caught fish and seafood
How much humans use of these resources and how fast the earth can regenerate them depends not only on one factor (human population, etc.) but on many, and each of them affects the others. Increasing cropland through conversion of forests to agricultural land may sound good, but will cost the loss of forests, biodiversity, and ecosystem services.
Many have and will surely challenge the WWF’s finding that we are in the middle of, and are pushing the earth to, an ecological overshoot situation. But is not that hard to see that our natural resources are finite and can only meet our needs for so long. As with most life issues, striking a balance between the two (reasonable demand and sustainable supply) is imperative.
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