This has been an inspiring, sharp, and important dialogue, addressing many of the critical sustainability science issues arising from the increasingly robust scientific evidence of accentuated global environmental risks. I would like to thank everyone for their constructive comments. I have learned a lot from the discussion, and I look forward to continued engagement. In the following, I will attempt to respond to a few of the threads running through the comments.
First, let me start with a general reflection of what planetary boundary science is and, perhaps most importantly, what it is not. I am glad that the core planetary boundaries analysis is criticized for not addressing root causes, solutions, governance issues, ethics, capitalism, and values. I am convinced that its merits, to a significant extent, arise from the fact that it decouples biophysical Earth system analysis from a human dimensions analysis of Earth system change. But this biophysical focus does not mean that the human dimensions are not an integral part of our research endeavors on planetary boundaries research (there have been over 80 scientific articles with planetary boundaries in the title or abstract since the 2009 publication, as well as over 3000 citations, many of which are in the social sciences). I am proud to have co-authored an article with Paul Raskin and Mike Gerst on a Great Transition analysis within planetary boundaries; an article with Maarten Hajer and others on the challenge of cockpit-ism; an upcoming op-ed in Project Syndicate with Kate Raworth on integrating human and biophysical boundaries; an article with Melissa Leach and colleagues on integrating PB thinking with the STEPs approach of the 3 Ds on Direction, Diversity, and Distribution (a human dimension approach to global sustainability); and contributions to the World Social Science Report 2013 with several of the above, to give a few examples.1
It is an important scientific strategy, in my opinion, to keep these lines of research separated at the diagnostics phase, precisely to avoid the critique that Noel Castree raises. I disagree that the PB science is normative in the sense that it “politicizes science.” The PB framework arises from two strands of major scientific advancements in Earth system science over the past thirty years (culminating only in the past five to ten years). First is the evidence that we have entered the Anthropocene and that we intrinsically depend on the Holocene state for modern world development. This, by the way, can be—possibly—considered a normative statement. I would agree that we can live outside of the Holocene, but there is no evidence that we can “responsibly” host 7, much less 9, billion people in a modern world outside of the Holocene. Second is that the Earth system, through interactions and feedbacks, responds in unexpected ways, characterized by shifts from negative/dampening to positive/reinforcing feedbacks that can trigger tipping points, causing abrupt and potentially irreversible state shifts in the Earth system.
I would like to thank Jill Jäger for her critical comment on the use of the word “stable.” I agree, of course, that we have had large environmental variability in the Holocene, in particular at the local and regional scale, but I think it is fair to say (1) that the Holocene is an inter-glacial state of the planet and (2) that it has proven to be remarkably stable (as compared to both glacial “jumpy” periods and earlier inter-glacials). Global average temperature has oscillated within ±1 °C, with larger regional sways. Compared to any other epoch, the Holocene stands out as a paradise of stability, our Edenic garden.
It is the emergence of this increasingly robust evidence of the advent of the Anthropocene, our dependence on the Holocene, and the risk of catastrophic tipping points that “naturally” has led science to the next incremental step in knowledge accumulation, that is, addressing Earth resilience. We see it in the guardrail research, in the tipping elements research, in the coupling of climate with the biosphere in Earth system analyses, and in the massive bulk of research on regime shifts within resilience science. However, we also see it in the establishment of centres like the Future of Humanity Institute (FHI) at Oxford and the Centre for Existential Risk research at Cambridge University. All in all, we have recognized that humanity is now capable of triggering shifts in the state of the Earth system as a whole.
The PB analysis is but the incremental and natural extension of this cumulative scientific advancement and evidence. It only attempts to answer two questions. First, what biophysical processes regulate the stability (capacity to remain in a Holocene-like state) and resilience (ability to maintain negative feedbacks—i.e., dampen disturbance) of the Earth system? Second, relying on the latest scientific knowledge, can we define quantitative boundary levels for key control variables for each of these processes beyond which science indicates a significantly raised probability of triggering shifts in feedbacks, i.e., potential state shifts away from the Holocene state? It is true that there are wide ranges of uncertainty for many of the nine. This is why we distinguish between transgressing boundaries (i.e., entering a zone of uncertainty) and crossing thresholds (i.e., passing points at which feedbacks change direction). It is also true that we do not have all the scientific knowledge needed to say precisely where the boundary position is, and for two of the nine, we cannot even provide global quantifications. And, true, the numbers evolve as science evolves. But, all this said, I do not see this as a normative framework, or one that is equivalent to what we have been doing over the past fifty years. To start with, the approach makes no assumptions on human ethics, needs, aspirations, or capacities to innovate and adapt. It “simply” attempts to define, for the Anthropocene, a biophysical safe operating space (a biophysical ceiling in Kate Raworth’s words, which, of course, must have a social floor). But, precisely in order to avoid the risk of being criticized for being normative or advocacy-oriented, we do not make any assumptions regarding human needs and possibilities, or on pathways to sustainability. We just attempt, based on our latest state of science, to define a biophysical space within which humanity has a high chance of preserving a conducive environmental state of the planet. Then, we can put humanity back into the safe operating space, and this is, certainly, where the excitement starts.
Several comments agree with the need for a deep mind shift. I land in the same conclusion. I do not make an illusion of trying to resolve how this is to occur; I only conclude that the natural scientific evidence leads to that conclusion. Again, my view is that just because I translate our planetary boundary analysis, and the assessment of a 1.6 % probability of 6 °C warming, based on IPCC’s conservative science assessment, to a need for a deep mind shift and a global transformation to world development with a stable Earth system, does not mean that (1) we politicize science or that (2) this would be a claim to resolve all problems. It simply opens the floor for trans-disciplinary collaboration.
Second, several commenters have made sharp points on issues of ethics and governance. I am extremely intrigued by the fact that applying PB thinking to sustainable development leads to the necessity of development within finite global budgets for planetary boundary “capitals”—a global carbon budget as well as finite budgets for P, N, land, and freshwater. This fundamentally changes the ethical agenda of how to share the remaining ecological space on Earth in a just way. It is not new—the global carbon budget is even raised in the IPCC Fifth Assessment Report—but it provides an integrated framework for a transition towards a more ethical approach to sustainable development in the Anthropocene. On governance, I, as Maarten Hajer knows, allow myself (perhaps naively) to maintain that navigating toward a prosperous future for humanity on Earth, under the rising global risks we face, will require strengthened global governance. This does not contradict or exclude diversity, poly-centricity, or multi-scale approaches to sustainability. But the urgency of the Great Transition is so evident that the world will require certain planetary scale agreements. This is a very interesting debate (and, I would again like to emphasize, not an integral part of the PB analysis as such), and to add some fuel to it, let me suggest that we may be approaching a new “Montreal Moment” for climate.
I think we all agree that the Montreal Protocol is an example of humanity operating as planetary stewards. Critics have always argued that the success with ozone cannot be applied to climate because (1) the industry was ready to move and (2) the problem was simpler—there was not a threat to economic growth. There is evidence that we may soon meet these two criteria. Solar, wind, biomass, and hydro are increasingly at grid parity with coal, oil, and natural gas—and possible to apply at scale. Just look at the rapid penetration of renewables in Germany, for example. We can envisage perfect substitution for energy, from fossil fuels to renewables, without undermining growth or livelihoods. On the contrary, more and more evidence suggests small-scale PV is more effective than coal investments to eradicate poverty. So my bet is on coupling global governance with local action, and I see policy measures as key to spur innovation in a sustainable direction in an era of rapid technological change. I agree with Marten Haajer, Marcel Kok, and Kathrin Ludwig when they stress the crucial role of “autonomous citizens, civil society initiatives, self-organized farmers, cities, and innovative companies take action.” When the state fails, such actors can play a key role in providing public goods and services, and in such a way also spur and put more pressure governments into action.
I am not entirely sure I fully understand the comments on “doomerism” and nudging, nor the reflections by David Maggs and John Robinson that the underlying assumptions of the planetary boundaries approach “tie our hands behind our backs to the extent that they ignore our agency in creating the pictures of the world we are confronted with and postulate a reductionist picture of human society and decision-making.” My view is precisely the reverse. It may sound a bit surprising and even arrogant, but I think the planetary boundaries analysis is potentially one of the most optimistic and “positive vision” triggering analyses around. Why? Yes, it raises the bar on the challenge, but, by doing so, it also raises the specification of what grand innovation/grand transformations must accomplish: “It is not a bridge we are building; it is a moonlander.” In other words, I think the “dire” analysis and the conclusion that we need to seek solutions that deliver prosperity within a finite Earth system can trigger transformative thinking (i.e., truly take us away from nudging and incrementalism), rather than hamper new ideas. And I would argue that there is some empirical support for this conclusion. Tough environmental regulations have over the years, generally after severe resistance at first, proven to spur innovation, functioning as a vehicle for, rather than a hindrance to, transformation. I agree that if today’s global risk analysis pushes people into despair, causing limits to innovative thinking, then we are in real trouble. But I see more indications that a vision of a decarbonized world economy, or a world fed from healthy and sustainable food systems, can trigger visions of opportunity rather than despair (particularly among business leaders).
To close, I agree with David Maggs, John Robinson, and Karen O’Brien’s reasoning around the importance of addressing issues of power structures, but the limited space did not allow me to elaborate on these topics further in the essay. I also agree that a strategic research priority is to explore the deep mind shifts and fundamental changes in economics, governance, etc., required to enable transformations that meet requirements for people and planet. I can think of no more important research and action agenda going forward.
1. Mike Gerst, Paul Raskin, and Johan Rockström, “Contours of a Resilient Global Future,” Sustainability 6, no. 1 (2014): 123-135, http://greattransition.org/archives/other/Gerst_Raskin_Rockstrom_Contours_of_a_Resilient_Global_Future.pdf; Maarten Hajer et al., ”Beyond Cockpit-ism: Four Insights to Enhance the Transformative Potential of the Sustainable Development Goals,” Sustainability 7, no. 2 (February 2015): 1651-1660, http://www.mdpi.com/2071-1050/7/2/1651; Melissa Leach et al., ”Transforming Innovation for Sustainability,” Ecology and Society 17, no. 2 (2012): 11, http://www.ecologyandsociety.org/vol17/iss2/art11/; International Social Science Council, World Social Science Report 2013: Changing Global Environments (Paris: UNESCO, 2013), https://www.oecd.org/fr/publications/world-social-science-report-2013-9789264203419-en.htm.
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