Pushing the boundaries.

“The difference between stupidity and genius is that genius has its limits.” – Albert Einstein

This past Thursday, January 15, Will Steffen of the Australian National University and seventeen co-authors generated a bit of media stir with the electronic publication of their paper in the journal Science: Planetary boundaries: guiding human development on a changing planet. Their paper merits a fuller read, but access to it is somewhat restricted. Suffice it to say for present purposes that the paper builds on a framework put forward in 2009 by a group led by Steffen and Johan Rockstrom from the Stockholm Resilience Center. While you can find a fuller summary of the framework in Wikipedia, an excerpt of that latter article gives the basics:

The framework of “planetary boundaries” is designed to define a “safe operating space for humanity” for the international community, including governments at all levels, international organizations, civil society, the scientific community and the private sector, as a precondition for sustainable development. This framework is based on scientific research that indicates that since the Industrial Revolution, human actions have gradually become the main driver of global environmental change. The scientists assert that once human activity has passed certain thresholds or tipping points, defined as “planetary boundaries”, there is a risk of “irreversible and abrupt environmental change”. The scientists identified nine Earth system processes which have boundaries that, to the extent that they are not crossed, mark the safe zone for the planet. However, because of human activities some of these dangerous boundaries have already been crossed, while others are in imminent danger of being crossed…

The proposed framework of planetary boundaries lays the groundwork for shifting approach to governance and management, away from the essentially sectoral analyses of limits to growth aimed at minimizing negative externalities, toward the estimation of the safe space for human development. Planetary boundaries define, as it were, the boundaries of the “planetary playing field” for humanity if major human-induced environmental change on a global scale is to be avoided…

…Transgressing one or more planetary boundaries may be highly damaging or even catastrophic, due to the risk of crossing thresholds that trigger non-linear, abrupt environmental change within continental- to planetary-scale systems. The 2009 study identified nine planetary boundaries and, drawing on current scientific understanding, the researchers proposed quantifications for seven of them. These seven are climate change (CO2 concentration in the atmosphere < 350 ppm and/or a maximum change of +1 W/m2 in radiative forcing); ocean acidification (mean surface seawater saturation state with respect to aragonite ≥ 80% of pre-industrial levels); stratospheric ozone (less than 5% reduction in total atmospheric O3 from a pre-industrial level of 290 Dobson Units); biogeochemical nitrogen (N) cycle (limit industrial and agricultural fixation of N2 to 35 Tg N/yr) and phosphorus (P) cycle (annual P inflow to oceans not to exceed 10 times the natural background weathering of P); global freshwater use (< 4000 km3/yr of consumptive use of runoff resources); land system change (< 15% of the ice-free land surface under cropland); and the rate at which biological diversity is lost (annual rate of < 10 extinctions per million species). The two additional planetary boundaries for which the group had not yet been able to determine a boundary level are chemical pollution and atmospheric aerosol loading.

The figure below is one of numerous depictions of the nine boundaries; tables and text in the Wikipedia link provide additional detail. One especially important and welcome feature is the emphasis on the zone of uncertainty characterizing the boundaries, and the careful nature of discussion of this uncertainty and its implications. The Wikipedia article also provides a portal to some of the debate that the original 2009 work inspired. In keeping with the spirit of Darwin’s quote on the home page of this blog, that debate may perhaps be the nine boundaries’ most useful contribution.


The current article updates the status of the nine boundaries. The authors find that four of the safe boundaries have been exceeded (the 2009 work listed only three): the level of carbon dioxide in the atmosphere;  biogeochemical cycles (in particular, the flow of nitrogen and phosphorous into the ocean); biosphere integrity (the extinction rate); and land-system change (deforestation). The authors also further develop the basic planetary boundary framework, introducing a two-tier approach to accommodate heterogeneity at regional levels; update the quantification of most of the planetary boundaries; argue that two of the boundaries – climate-change and biosphere integrity – are “core,” and more.

Reading this newest update to the nine-boundaries discussion prompts two thoughts. First, the entire paper speaks of trends but stops short of estimating a time frame during which each of the safe boundaries might be exceeded (unless it has been exceeded already). That’s undoubtedly wise in many respects. However, our community is in the business of forecasts, and we’ve learned that making forecasts has a marvelous ability to focus minds, foster accountability, make evaluation more pointed, and thus accelerate the advance of knowledge and understanding. By analogy, consider how hurricane forecasts of landfall (both location and time) drive societal response. Much of this is clearly going on across the IPCC realm, but we’re only scratching the surface; we could perhaps use such a “stretch” goal[1]. Surely it would help to have an idea, however rudimentary, of “how much time we have,” and how we might buy ourselves more such time.

Second, nine boundaries for the globe as a whole, with infrequent updates, even by a large group such as the eighteen authors of this paper, or the hundreds or thousands of contributors to the IPCC reports, leaves most of the world’s seven billion people as uninvolved spectators. When we see excellent reports such as this one, the rest of us might do well contemplate the personal boundaries that limit our own behavior or accomplishments or contributions to global problems such as this one… and explore how we might expand or push those boundaries back a bit.

[1][1]. Elsewhere in this LOTRW blog, and in the book by the same name, the suggestion is made we should follow the example set by the Bulletin of Atomic Scientists, with its doomsday clock.

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One Response to Pushing the boundaries.

  1. The problem with both the original and this update is that while it’s hard to argue with the categories (sort of like being against motherhood!), the boundaries themselves seem arbitrary and not really bounding. We’ve far exceeded 350 ppm CO2 – we haven’t seen anything like the Doomsday effects expected of a true tipping point. 10 extinctions per million species – who’s counting?

    And while, as a scientist, I like the idea of prediction, I have to harken back to the wisdom of the Yogi [Berra] – “It’s tough to make predictions, especially about the future.” Our efforts might be better spent firming up the boundaries first.

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