Planetary Boundaries

Where do you draw the line?

A group of earth-system scientists in 2009 proposed a new framework of “planetary boundaries” that attempted to comprehensively consider every aspect of humanity’s transformation of the environment, from climate change to biodiversity loss. They wanted to establish an easily understandable guide to what was left of an optimum “safe operating space for humanity.” Beyond these boundaries, the researchers said, there is a risk of “irreversible and abrupt environmental change” that would make the planet significantly less habitable for humans.

The researchers, led by Johan Rockström of the Stockholm Resilience Centre and Will Steffen of the Australian National University, identified nine such boundaries. Currently, the Earth appears to have crossed the boundaries of climate change, biodiversity loss, and the nitrogen cycle (but not the phosphorus cycle).

While endorsed by a number of organizations, the debate over this approach centers on whether these boundaries represent rigid, permanent upper limits to human societal growth, or whether should be considered more like a rule of thumb.

There is a sense of unease in some quarters at the presumption of global governance that the concept implies. Others worry that the concept is a bit Malthusian – that planetary limits on people and resources limit growth.

A number of self-styled ‘eco-modernists’ such as the Breakthrough Institute, a U.S. environmental organization, disagree whether limits can truly have meaning for our species, given our historic ingenuity in the face of obstacles, or that the concept of carrying capacity can apply to humanity.

“Ever since early humans discovered fire and the benefits of collaborative systems such as collective hunting and social learning, human systems, not the classic biophysical limits that still constrain other species, have set the wider envelope for human population growth and prosperity,” argues ecologist Erle Ellis, an associate of the Breakthrough Institute.

If you want to read more, a special issue of Nature explored the topic in great detail, including critical commentaries from researchers not associated with the original paper. The Stockholm Resilience Centre website contains videos and a host of further research links. For the other side, Ellis’ essay for the Breakthrough Institute, “Planet of No Return,” also offers a series of further reading recommendations.

Critics of a Malthusian reading of the planetary boundaries concept include Steve Rayner, Ted Nordhaus and Michael Shellenberger, and Keith Kloor.