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A timely reminder of the real limits to growth

By Bill McKibben - posted Monday, 19 October 2009

Let’s play doctor. I’m sitting there in a white coat looking at my clipboard and I say: “Hmmm, your cholesterol is going up. If you keep eating this way, you’re going to have a heart attack some day.” You hear that, and you stop on the way home for a bacon double cheeseburger.

But now imagine I’m sitting there in my white coat looking at my clipboard and all of a sudden I whistle, and say: “Your cholesterol is off the charts, man. You’re in the zone where people have heart attacks all the time. You better hope you get it down before the stroke.” You hear that, and you stop on the way home for some Lipitor and a pair of running shoes.

We’ve known for a very long time now that, in some vague way, we were headed for trouble. Limits to Growth was published in 1972, and its assorted charts and graphs made remarkably clear that, as the authors of that seminal book put it at the time, “If the present growth trends in world population, industrialisation, pollution, food production, and resource depletion continue unchanged, the limits to growth on this planet will be reached sometime within the next one hundred years. The most probable result will be a rather sudden and uncontrollable decline in both population and industrial capacity.”


But “the next hundred years” must have seemed a comfortingly long time, because - though Limits to Growth was the biggest-selling environmental book of all time, with 30 million copies sold - it wasn’t enough to divert our trajectory.

I thought of Limits to Growth last week, when Nature published a lead article by a large and illustrious team headed by the Stockholm scientist Johan Rockstrom. Titled “A Safe Operating Space for Humanity,” it set boundaries for nine interlinked planetary thresholds, arguing that if we crossed them we risked destroying the “unusual stability” that has marked the Holocene, which is the name scientists use for the last 10,000 years, the period when civilisation arose.

The almost-good news is, we don’t know enough about two processes that lead to crossing those thresholds - the loading of aerosols and particulates in the atmosphere, and the effects of chemical pollution - to know if we’ve already gone too far.

The bad news is, we’re close to crossing most of the rest of the boundaries. The authors estimate that we currently allow 9.5 million tons of phosphorus to flow annually into our oceans, mostly because of fertiliser use, and that past 11 million tons we may well trigger “large-scale ocean anoxic events”. Ozone concentrations in the atmosphere - 290 Dobson units before the Industrial Revolution and 283 at present - can’t dip below 276 without catastrophe, the authors note.

Oh, and the worse news is, we’re already well past three of the borders. We’re removing almost four times as much nitrogen from the atmosphere for human use as is safe, and the result are things like wide-scale water pollution and the addition of heat-trapping gases like nitrous oxide into the atmosphere. The species extinction rate, the authors argue, is probably 10 times the tolerable level of 10 species per million species per year, though they add that they’re less certain of this than other numbers. “However, we can say with some confidence that Earth cannot sustain the current rate of loss without significant erosion of ecosystem resilience.”

Most importantly, they assign a number to the safe maximum value for carbon dioxide in the atmosphere: 350 parts per million. This was the first of these limits to gain wide public notice. Since NASA scientist James Hansen and his team first broached this number in December 2007, some of us have built a global movement around it (, which will culminate on October 24 with rallies and events in most all the world’s nations, gatherings designed to drive this particular boundary deep into the public consciousness and hence move the climate negotiations at Copenhagen closer toward the targets science has been demanding. Since we’re at 390 parts per million now, and rising 2 ppm per year, it’s a last-ditch effort - but it’s amazing to see how the number rallies people, how it takes the abstract and makes it real.


In a sense, of course, these numbers are both over-exact (351 is obviously not damnation, nor 349 salvation) and in certain ways superfluous. If you were paying attention recently either to new data (that the ice sheets of Greenland and the Antarctic are melting much more rapidly than expected) or to scary pictures (the giant dust storm that engulfed drought-stricken Sydney), then you already understand at some level that we’re moving quickly out of the stable balance of the last 10 millennia. The photos of record flooding in the Atlanta area seemed particularly powerful to me, because they showed newly built tract homes submerged to the second story. Newly built homes are usually off the floodplain, away from the path of the 100-year storm - but in this case that didn’t help, because this was bigger than the 100-year storm. One river rose 11 feet above its previous peak.

Still, the new Nature paper helps enormously. It helps by making clear how interlocked these various phenomena are. Carbon is driving ocean acidification, for instance, just as it’s raising temperature; global warming will accelerate the species extinction that already comes from habitat destruction.

It helps too by removing the temptation for delay - a temptation that never flags. Only true ideologues or the most oblivious among us thought that we’d never reach the “limits to growth”, but plenty of people convinced themselves they were far enough away that they’d be someone else’s problem. You could hear a bit of that attitude on display at the United Nations last week, as President Obama gave an uninspired speech on climate change, explaining all the reasons that significant progress would be hard (the Congress, the overriding imperative to grow the economy), and admonishing people not to hold out for “the perfect” solution.

But the perfect solution is no longer on offer, as Rockstrom et al make abundantly clear. They’re doing us an enormous service by attempting to isolate the bargaining position of the natural world, a bargaining position that we really might want to respect. If the planet says 350, then it doesn’t matter that the US needs to get out of an economic rut, or that China still has lots of peasants who would like to move to the city. We’re going to have to find non-carbon ways to do those things, because the planet is unlikely to suddenly say, “Oh well, 450 then”. The laws of nature aren’t amendable like the laws of man.

Respecting these limits, now that we know they’re there, becomes the central human task. Just as the man with the high cholesterol needs to think at every turn about his diet, his exercise, his medicine, so we too have lost the right to casual obliviousness that goes with not knowing. If we choose to ignore the warnings, we’re not some 14-year-old smoking because his friends think it looks cool, or even the pack-a-day lifer with other things on his mind. Now we’re the lung cancer patient trying to sneak cigarettes in the ICU.

Yes, it’s hard to change ways of life, and hard to break addictions, and hard to turn your economic systems and political goals away from the constant expansion that have been their target for more than 200 years. But now we know - with the cold precision offered by numbers - that there’s something that’s harder to imagine, which is going on as we’ve been going.

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First published by Yale Environment 360 on October 1, 2009.

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About the Author

Bill McKibben is a scholar in residence at Middlebury College. His The End of Nature, published in 1989, is regarded as the first book for a general audience on global warming. He is a founder of, a campaign to spread the goal of reducing atmospheric carbon dioxide to 350 parts per million worldwide. His most recent book is American Earth, an anthology of American environmental writing.

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