One Planet Is Enough

We often hear the story of humans voraciously exploiting the world’s resources and living way beyond Earth’s means. On “Earth Overshoot Day”, campaigners such as the Global Footprint Network claim that, by August 2, we have already exhausted this year’s supply of natural resources and Earth is now sliding into “ecological debt” for the rest of 2017.

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Globe In Hand

For more than a decade, the World Wildlife Fund and other conservation organizations have performed complicated calculations to determine our total “ecological footprint” on the planet. In their narrative, population growth and higher standards of living mean that we are now using 1.7 planets and are depleting resources so quickly that by 2030, we would need two planets to sustain us. If everyone were to suddenly rise to American living standards, we would need almost five planets. The message is unequivocal – WWF tells us we face a looming “ecological credit crunch”, risking “a large-scale ecosystem collapse.”

But this scare is almost completely fallacious. The ecological footprint tries to assess all our usage of area and compare it with how much is available. At heart, this is a useful exercise, and like any measure that tries to aggregate many different aspects of human behavior, it tends to simplify its inputs.

Some of these simplifications are valid. It is clear that roads, housing development and food production all take up valuable space on our planet. This part of the ecological footprint is a convenient measure of our literal footprint on earth. But roads and housing only takes up about 3.8% in their latest numbers. And even food production only uses about a third of all productive land. Moreover, as better technology achieves ever higher yields, it is likely that this total area will not increase much and may even decrease over time.

The area used by forests products and grasslands make up less obvious simplifications. The production of wood and paper takes up 16% of the world’s area, but this is still less than half the world’s existing forests. And while this 16% suggests that the area is somehow occupied and blocked from other uses, the truth is that while the wood products are growing, they form real forests that are part of the planetary beauty. It’s the same case with grasslands, which are estimated to take up around 9% of the world’s area. And fisheries are even less intuitive, as areas of fishing grounds are squeezed into land area. While we’re still attempting to find an estimate of the surface area required to sustainably support a country’s catch, the current total is a fairly small 5%.

In total, all of the somewhat problematically defined areas sum to 67% of the world’s biologically productive area. There seems to be little problem here – one earth is clearly enough.

What makes the ecological footprint exceed the available land is CO₂ emissions. Clearly it is not obvious how to translate CO₂ into land area. So the ecological footprint decided to get around this by defining the area of emissions as the area of forest needed to soak up the extra CO2. This single factor makes up 101% of the planetary land area and is the only reason why we suddenly need more than one planet.

In essence, we are being told that we ought to cut CO₂ to zero, and to plant trees to achieve that, meaning that we’d have to plant forests today on all of the planet’s available area. Since we’re already using 67% that’s why they can tell us that we’re running out of planet. But that message is clearly unreasonable.

Not only is it dubious that we would have to reduce CO₂ to zero (though we definitely have to reduce it significantly in the long run). But much more important, choosing forests to soak up CO₂ is the absolutely most inefficient way to cut CO₂. The standard assessment finds that every year we emit one tonne of CO₂, we should plant 2000m2 of forests to soak it up. But if we planted wind turbines or solar panels instead, we would need only about 30m2 or less to avoid a ton of CO₂ emitted. And we wouldn’t even need to place them on biologically active land (we could place the solar panels on rooftops or in the desert, and wind turbines in the ocean). Suddenly the 101% drops to less than 2% -- or possibly zero.

The academic literature around the ecological footprint has known this Achilles heel for many years. One of its staunch defenders said already in 2002 that defining the CO₂ footprint as “the area of land needed to absorb the carbon emitted by burning fossil fuels is regarded by most eco-footprinters, including especially ourselves, as being hard to defend.” That is the background for academic articles entitled “Why the ecological footprint is bad economics and bad environmental science” and a recent review found that “ecological footprint measurements, as currently constructed and presented, are so misleading as to preclude their use in any serious science or policy context.”

We clearly use less than one planet, and looking into the future with better agricultural and renewable technology, the use is likely going to diminish. Instead of panicking over prophecies of unsustainable footprints, we should focus on the matters at hand: pulling millions more out of poverty while funding the sort of innovation that will eliminate future risks of pollution and make our land more productive. That way, we will ensure that one Earth keeps being enough for all of us.

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