Civil Engineering Reference
In-Depth Information
for the years 1961 to 2008. They are produced by an organisation called the
Global Footprint Network
, which uses data provided by the United Nations. A
major source of interest and funding for this work comes from the EU. The Global
Footprint Network's vision is to make the ecological footprint as prominent a metric
as GDP by 2015.
The basis of the system is to provide a way of measuring how much productive
land is required to sustain life in terms of producing food, energy, water and timber
and carrying away the associated wastes. The calculation of the demands we place
upon the planet can be made at the individual, national and global levels. This is
done by taking resource use and comparing it to what is actually available. The
convention is to state the data with reference to the global hectares available per
person. This is explained in the next section.
Measuring the Ecological Footprint
The calculation begins with the assumption that productive land upon which life
depends could be anywhere in the world. This seems reasonable, as people of one
nation usually consume resources and ecological services from all over the world.
The ecological footprint calculations are, therefore, stated in global hectares (gha).
A global hectare is one hectare of biologically productive space. In 2008, the globe
had 12 billion hectares of biologically productive area corresponding to roughly
one-quarter of the planet's surface. The 12 billion hectares include 2.4 billion
hectares of water and 9.6 billion hectares of land. The land area includes
1.8 billion hectares of cropland, 3.4 billion hectares of grazing land, 4 billion
hectares of forest land, and 0.2 billion hectares of built-up land. Non-productive
marginal areas, such as deserts, ice caps, and deep oceans, are not included in the
12 billion global hectares of biologically productive space (GFN 2012).
To express the capacity available to each person, the 12 billion global hectares
of biologically productive area are divided by the number of people on earth.
The world's population was approximately 6.7 billion in 2008, giving 1.8 global
hectares per capita. This means that, in principle, the average amount of ecological
productive capacity (the biocapacity) that exists on the planet per person is
1.8 global hectares. (This simple calculation of available biocapacity assumes that no
capacity is set aside for the demands of wild species.)
If each person could survive on 1.8 hectares, or less, the world would be
sustainable. However, the latest ecological footprint accounts published by the
Global Footprint Network indicate that we are far away from achieving sustainable
development. The figures show that, on average, every person on earth is taking
50 per cent more from the planet than it can naturally regenerate. In other words,
humanity's ecological footprint is 50 per cent larger than the planet's capacity to
produce these resources. This means that there is an ecological overshoot - it now
takes about one year and six months for the planet to regenerate what we use in
a single year. You might well ask how can this be possible? Well drawing on
the financial analogy used by WWF (2012: 40) just as it is possible to withdraw
money from a bank account faster than the interest that this money generates
accrues, renewable resources can be harvested faster than they can be regrown. But
