Monday, August 3, 2009 - 2:50 PM

OOS 7-5: The human eco-footprint, biophysical limits, and the really inconvenient truth about sustainability

William E. Rees, University of British Columbia


Like all species, populations of H. sapiens tend to expand to occupy all accessible habitats and to consume all available resources. However, humanity’s competitive superiority has enabled our species to become the dominant macro-consumer in most major ecosystem types on the planet—we may now well be the both most successful vertebrate predator and herbivore ever to inhabit the Earth. This presentation uses ecological footprint analysis (EFA) to ask whether the resultant persistent growth of the human enterprise is breaching critical biophysical limits and putting civilization at risk. EFA estimates the total area of productive ecosystems that any specified population requires on a continuous basis to satisfy its demands for renewable resources and to assimilate its wastes.


The method shows that 85 countries currently exceed their domestic bio-capacities and must compensate for significant ‘ecological deficits’ through trade and by exploiting the global commons. These countries survive and grow by shuffling carrying capacity around the world and by depleting stocks of natural capital in countries that still have biophysical surpluses. Unfortunately, globalization eliminates any direct negative feedback on the offending populations—long-distance trade blinds high-income consumers to ecosystems degradation half a planet away. The process thus continues, ensuring that the entire human enterprise will reach global limits simultaneously with no buffering capacity. Indeed, the world community is already in a state of global overshoot—prevailing levels of resource consumption and waste production exceed the sustainable regenerative capacity of the ecosphere by almost 30%.  Persistent overshoot is a sufficient condition for societal collapse. To avoid calamity, humanity must quickly reduce its aggregate eco-footprint below the long-term regenerative capacity of critical ecosystems. At 9.2 global average hectares (gha) per capita, North Americans’ eco-footprints are about 3.4 times larger than the world average (2.7 gha) and 4.4 times larger than available per capita biocapacity (2.1 gha). For sustainability with equity, North Americans should therefore be taking steps to lower their eco-footprints by almost 80% to free up the ‘ecological space’ necessary for justifiable growth in the developing world. This is technically possible even while increasing long-term well-being. However, the necessary policies to achieve the implied radical restructuring of the economy and personal lifestyles are unlikely to be implemented in the foreseeable future. Techno-industrial society remains in deep denial of biophysical reality and mesmerised by the myth that material efficiency and technological substitutions are decoupling the human economy from nature.