Steve Rayner, from Oxford University, has written a guest post on planetary boundaries over at Roger Pielke Jr.’s blog.

The concept of planetary boundaries was introduced in two main papers, here and here, as a way to ascertain how human activities are affecting different earth systems: water, nitrogen cycles, the atmosphere and so on. Here is a visual image.

In an earlier post, which generated a number of responses, Pielke had characterized planetary boundaries as a kind of power grab. The worry here, for Pielke, is that science becomes the arbiter of normative and political legitimacy, when in fact science is just one tool, and a certain kind of tool at that.

In the more recent post, by Steve Rayner, he concludes that:

“The framing of planetary boundaries as being scientifically derived non-negotiable limits, obscures the inherent normativity of deciding how to react to environmental change. Presenting human values as facts of nature is an effective political strategy to shut down debate.”

My problem with this framing is that it presumes that there is a divide between facts and values. But that supposition has frequently been shown false, by Hilary Putnam, Bernard Williams, Quine, Wittgenstein (the list goes on…). So it doesn’t make sense to me to frame the debate in this way. And I do think there is a debate here.

The debate is one that has been going on around the idea of ecological ‘limits’ since the 1970s. And it brings to bear all sorts of issues about how we scale human activities to a certain imagination of Earth systems. Scale, here, is a ratio of time to space. And our imagination of the temporal and spatial effects of human activities are projected against some canvas. Early on it was Gaia, then a static view of a stable earth, and now a view of non-linear and complex systems.

It will be interesting now to follow this debate to see if it unfolds in any new ways. I have my doubts, since it seems positioned on roughly the same axes of similar ones; over in this corner “facts” and weighing in over here “values”.