Do ecological footprints make poor predictors?

The recent “doomsday prophecy” of the planet’s ecological footprint by the World Wildlife Fund for Nature is scientifically flawed, says a new report. Rather than needing an extra planet to cope with future needs, humankind will continue to live below the Earth’s maximum biocapacity beyond 2050. The ecological footprint model “is a weak analytical tool that should not be applied in sustainability discussions”.


In their report, Assessing the Ecological Footprint: A look at the WWF’s Living Planet Report 2002, the Danish Environmental Assessment Institute where controversial environmental skeptic Björn Lomborg is director (see related story) argues that WWF predictions of the planet’s ecological footprint are “built on a weak scientific foundation”. The WWF has assumed there will be no conversion to renewable energy over the next thirty years, says the Institute. “The ecological footprint rests on a restrictive understanding of sustainability and it makes use of questionable assumptions – the most serious being that we should raise forests in order to solve the problem of carbon dioxide emissions.”

In the Living Planet Report the WWF predicted that, with no changes in today’s lifestyles, two planets would be needed to meet humankind’s needs by 2050. In the best case scenario, with technological advances, we would still require 1.2 planets to sustain us.

The predictions were based on the charity’s calculations of humankind’s ecological footprint, including crop, grazing, forest and built-up land use, fishing and energy consumption. The largest factor in the footprint was energy use. In the World3 model used by WWF, the model assumed that all carbon dioxide emissions from fossil fuel burning would have to be countered with forest planting, requiring an extra 2.5 billion hectares of land to neutralize the CO2. Renewable energy was not included.

“Failing to acknowledge that at least some degree of substitution is possible could lead to a biased ecological footprint,” warns the Institute, which criticizes the WWF report on that point. In its calculations, says the Danish report, the WWF omitted gradual conversion to renewable energy and underestimated technological progress, as did the infamous Limits to Growth report published in 1972. In fact, argues the Danish Institute, Limits to Growth predicted that the world would run out of oil by 1992, and that food prices would rise so much that people would starve by 2000. “These were the predictions of the World3 model – the model that is also used in the Living Planet Report,” says the Institute.

The Danish report recalculated the ecological footprint, assuming partial replacement of fossil fuels with renewable energy. Compared with the WWF, which claimed that the Earth would need 2.48 billion hectares of planted forests to sequester CO2, the Danish report predicted that the Earth could produce 50% of its energy needs with only 0.17 billion hectares planted with wind turbines, reducing land requirements by 93%. “A boy born today will, by this calculation, put much less strain on the ecological system compared to his parents,” says the Institute.

The Institute also warned that their own calculations should not be viewed as a better footprint, because there is no ‘right’ ecological footprint. “Rather, our own calculation is used to illustrate the arbitrary nature of the calculations behind the footprint size.”

However, the WWF asserts that ecological footprints are simply snapshots of potential futures, if the human race were to continue along given paths.

“The ecological footprint projection merely documents the demands of human consumption in comparison with the biologically productive capacity of the planet; it does not imply whether such a future is possible,” says the WWF report.

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