by Judith Curry
A new study published study in Nature alerts to impending catastrophic developments – this time not mainly based on climate change impacts but on wider developments caused by resource use.
Abstract. Localized ecological systems are known to shift abruptly and irreversibly from one state to another when they are forced across critical thresholds. Here we review evidence that the global ecosystem as a whole can react in the same way and is approaching a planetary-scale critical transition as a result of human influence. The plausibility of a planetary-scale ‘tipping point’ highlights the need to improve biological forecasting by detecting early warning signs of critical transitions on global as well as local scales, and by detecting feedbacks that promote such transitions. It is also necessary to address root causes of how humans are forcing biological changes.
Nature 486, 52–58 (07 June 2012) doi:10.1038/nature11018 [link] to abstract
[Link] to full paper
The point of the paper seems to be speculation on a possible Dragon King (the paper uses the term tipping point) associated with an ecosystem tipping point. Here is what I like about the paper:
- it presents a scenario for a possible tipping point/Dragon King, and provides reasoning for the plausibility of such a scenario. This is a difficult thing to do, and arguably an important thing to do.
- it takes a comprehensive look at ecosystem stresses (climate change plays a relatively minor role)
- it integrates information from paleontology, macroecology, population biology and ecological network theory.
- it is honest about the uncertainties in the various aspects of the study
What I don’t like about the paper is that in the final paragraph, it leaps to making sweeping policy recommendations:
Diminishing the range of biological surprises resulting from bottom-up (local-to-global) and top-down (global-to-local) forcings, postponing their effects and, in the optimal case, averting a planetary-scale critical transition demands global cooperation to stem current global-scale anthropogenic forcings. This will require reducing world population growth and per-capita resource use; rapidly increasing the pro- portion of the world’s energy budget that is supplied by sources other than fossil fuels while also becoming more efficient in using fossil fuels when they provide the only option; increasing the efficiency of existing means of food production and distribution instead of converting new areas or relying on wild species to feed people; and enhancing efforts to manage as reservoirs of biodiversity and ecosystem services, both in the terrestrial and marine realms, the parts of Earth’s surface that are not already dominated by humans. These are admittedly huge tasks, but are vital if the goal of science and society is to steer the biosphere towards conditions we desire, rather than those that are thrust upon us unwittingly.
Further, what is possible versus plausible is very fuzzy here. IMO the proper way to interpret this is as a possibility; further research is needed to establish the plausibility (and likelihood) of such a scenario.
Reaction: Huffington Post
An article in Huffington Post turns the speculation of a tipping point into a prediction:
Earth is rapidly headed toward a catastrophic breakdown if humans don’t get their act together, according to an international group of scientists.
Writing Wednesday (June 6) in the journal Nature, the researchers warn that the world is headed toward a tipping point marked by extinctions and unpredictable changes on a scale not seen since the glaciers retreated 12,000 years ago.
“There is a very high possibility that by the end of the century, the Earth is going to be a very different place,” study researcher Anthony Barnosky told LiveScience. Barnosky, a professor of integrative biology from the University of California, Berkeley, joined a group of 17 other scientists to warn that this new planet might not be a pleasant place to live.
JC question: How to interpret “very high possibility”? IMO, “very high possibility” is not defended in the paper.
Reaction: Forbes
Tim Worstall in Forbes has an interesting article on the paper entitled “Nature on Uncertainty: Climate Change is Less Important Than We Thought.” Excerpts:
The argument put forward is that there are things other than climate change which might cause the entire breakdown (or less emotionally, substantial and unpredictable change in) the environment and ecosphere that supports us all.
They specifically point to the cumulative impact of x billions of human beings on the planet. We do each have an impact and more of us can be assumed to have a greater impact certainly. They go further and point to, just as one example of their argument, the way in which population rise could lead to a phase change, a chaotic and of unknown outcome, rapid and irreversible change in our environment.
Which brings us on to thinking about the trade off between economic growth and emissions and climate change.
We know, because we can see it in any and every society anyone has ever studied, that economic growth leads to falling fertility rates. Thus, if we fear being buried under 27 billion other humans we should be arguing for some more economic growth to reduce the likelihood of that happening.
So now we have two things to worry about. Both the emissions which lead to climate change and also low growth which leads to rising population levels. And yes, we really do have a trade off between the two. We know that, absent de-carbonisation of our energy system, greater economic growth leads to higher emissions. Yet higher economic growth leads to lower population growth at the cost of those higher emissions.
Similarly, if we don’t have the economic growth which reduces population then we’re all going to be swamped with 27 billion of our fellows and we lose the environment and the ecosphere anyway. Thus the discovery of this new threat changes the correct balance, the optimal strategy, to deal with matters.
We should now happily move to more economic growth in order to reduce population pressures. That is, as a result of this new threat accept higher climate change in order to beat the population problem.
I’m quite certain that this isn’t the way the authors of the paper expected it to be taken: but it is still true that this is the way it ought to be taken. If population growth is a threat as real and dangerous as climate change then we really should be willing to put up with a bit more of the latter in order to deal with the former.
Reactions: Keith Kloor on Planetary Boundaries
Keith Kloor has a very good post on planetary tipping points [here], check it out.
JC comments: IMO, the issue of human impacts on ecosystem services should be the main issue of environmental concern. As pointed out in the Nature article, these impacts include land use, agricultural pollutants, burning of fossil fuels, all of which are tied to population growth. The role of AGW in all this is smaller than commonly considered. The interesting thing to me is whether this broader perspective will influence the forthcoming discussions at Rio +20.