This use of nature is measured in this report, nation by nation great deal of research to determine where their exact locations are. To simplify, the occupied space is calculated by adding up the areas with world average productivity that are necessary to provide us with all the ecological services we consume. Now, these ecological footprints can be compared to the biological capacity available within each country. The report examines 47 nations discussed by the World Economic Forum's Global Competitiveness Report plus 5 others Together, these 52 nations house 80 percent of the world population and generate 95 percent of the World Domestic Product. The ecological footprint measures our dependence on nature.
Every nation depends on ecological capacity to sustain itself.
Measures of carrying capacity and human impact on the Earth Studies about nature's capacity to support human life go back many centuries. Some focus more on energy requirements, others on non-renewable resources, and others again on photosynthetic potentials. Much intellectual ground-work was laid in the 1960s and 1970s. Examples are Eugene and Howard Odum's eMergy analysis examining systems through energy flows, Jay Forrester's advancements on modelling world resource dynamics, John Holdren's and Paul Ehrlich's IPAT formula, or, in the spirit of the International Biological Programme, Robert Whittaker 's calculation of net primary productivity of the world's ecosystems. As most of them are compatible, results from one approach strengthen the others.