The energy component of the footprint, dominated by use of non-renewable fossil fuels such as oil, coal and gas, increased nearly 700 percent in the 40-year period surveyed, from 1961 to 2001.
The world has some 28 billion acres of productive land and ocean to meet the needs of 6.3 billion people-an average of 4.4 acres per person. At current rates of consumption, however, the global ecological footprint requires an average of 5.4 acres' productivity per person-roughly 20 percent more than what can be sustained today's levels.
"We are spending nature's capital much faster than it can be regenerated. Collectively, we are bequeathing to our children the most dangerous budget deficit of all, an ecological debt of growing proportions," said Richard Mott, WWF's Vice President for International Policy.
