Tipping Points, Global Warming and the Balance of Nature

Tipping points are in the news these days because some of the well-known scientists who are concerned about global warming keep telling us that the Earth — the Earth’s global environment, that is — is nearing a tipping point.  The idea is that the environment may undergo changes from which there will be no return; the Earth’s environment will figuratively fall off a cliff.

Underlying this belief that our environment has tipping points and we might be nearing one is a deeper belief: that the Earth’s environment is stable, that undisturbed by human influences it would be constant, or close to it.  Allied with this is the belief that our own actions are pushing the Earth toward the edge of a tipping point in ways that have never happened before.

The idea that our environment — nature, as it used to be called — is pretty much unchanging except for what we do is an ancient belief. It goes back to the Greek and Roman philosophers, who expressed it as the great Balance of Nature: that nature undisturbed achieves a permanence of form and structure, and that even when disturbed by us, if we then leave it alone, it will return to its harmonious constancy.

That idea has followed Western civilization down the ages, and in the 20th century was a fundamental belief even among ecologists — scientists who study the relationship between living things and their environment.  But as I’ve shown in my book Discordant Harmonies: A New Ecology for the 21st Century, nature has always changed.  All the climate reconstructions show that change is its only constant property.  To be more technical about this, modern science tells us that natural ecological systems and their environment are non-steady-state systems.  The old idea about nature being constant and able to return to its constant state after disturbance is based on a classical idea of stability — the stability of a machine, like the pendulum of an antique grandfather clock.  Once set in motion, the pendulum goes back and forth, but gradually friction slows it down and it comes to rest exactly where it started.

One of the things that makes it hard to accept the view of environment and ecosystems as out-of-steady-state and part of non-steady-state systems is that we haven’t had ways to think about how such systems change over time.  To make that possible, years ago I and my colleague Matthew Sobel — an applied mathematician, economist, and William E. Umstattd Professor at Operations Research at Case Western Reserve University — wrote a paper called “Stability in Time-Varying Ecosystems.”  (The paper was originally published as Botkin, D.B. and M.J. Sobel, 1975, “Stability in time-varying ecosystems” in  American Naturalist 109: 625 – 646.)

Briefly, we coined and defined two new terms for ecological systems that insist on changing all the time: persistence and recurrence. Instead of expecting an ecosystem, say of tundra near Barrow Alaska, or a population, say of polar bears, to remain constant, we expect instead that their numbers will vary, but within a certain range. This means the bear population will persist within certain limits, an upper and a lower number.  We call this persistence within bounds.  If we take actions that we think might harm the polar bear populations, we can check if there is an effect by comparing its past persistence with current ranges of variation.  (That is, of course, if we have the data to do this.  If we don’t, we’re out of luck as scientists and our management of polar bears lacks an important scientific base, but that’s another story.)

Recurrence is similar.  If an ecosystem or population is recurrent, then the condition it is in now will occur again in the future.  If a population is declining and on its way to extinction, its current population size is nonrecurrent.  Here’s another example.  In 1938 there were only 18 whooping cranes, and there was concern that this species would go extinct, and steps were taken to protect their habitat — their wintering grounds at Aransas National Wildlife Refuge, Texas and their summering grounds at Ramsar Wetlands in northern Canada.  This helped their population to increase greatly, and by 2007 scientists counted 237 at Aransas.  We who admire these cranes hope a population low of 18 never recurs — the population never gets that low again, but that 400 or even more could.

Tipping points don’t work for non-steady-state ecological systems, because they are always changing, kind of sloshing around from one condition to another, and they don’t really have cliffs to fall off of.  Life has persisted on Earth for about 3.5 billion years, during which it has evolved, changed, and adapted to changes many times.  Indeed, many of the changes life has adapted to were brought about by life itself, which has altered the environment locally and globally, adding to that sloshing among system states. Living things and their ecological systems do change a lot.  We can talk about changes that we like and those we don’t like, changes we consider natural or unnatural, but speaking of these as tipping points gets us off the track, away from how these things really work, and interferes with understanding what we could do, want to do, and even should do.

These are the general ideas.  If you want to get into the details, please read Matt Sobel’s and my paper.  Meanwhile, realize that tipping points only happen to steady-state systems, and our environment and ecosystems are not that kind.  There are many helpful ways to consider and discuss the possible effects of global warming.  Tipping points is not one of them.

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Comments

  1. Greg Studen says:

    I do not understand the argument of this article.

    Although “Life” may be highly resilient, individual species are much less so, and individual organisms even less so. Take human life for example. We require an environment within a certain temperature range (natural or artificially maintained), a steady supply of food and water, oxygen to breathe, and protection from predation and disease. If any of these are disrupted sufficiently from a range (using suitable measures), we die. If they are disrupted for enough of us, the whole species dies. These are real thresholds, and they hold for all species. Logically, there is also a threshold for the possible extinction of all life on Earth; say from a large asteroid impact or the eventual death of the sun.

    The whooping crane example just proves the point that environments have to be carefully regulated, by natural processes or human intervention, in order to maintain species with fairly specific requirements.

    Here are a few examples from possible global warming scenarios. If sea levels rise and tropical storms become more fierce, millions will die in Bangladesh. For them, this is a pretty big tipping point. More generally, if the climate warms and dries to the point where we can’t produce enough food for support human populations, millions more may die, including us. Ocean warming and increasing acidity are threatening the ecosystems of coral reefs, pelagic micro-organisms, and food chains. Contrary to the authors, I look ahead and see many cliffs on the near and far horizon.

    There’s obviously some sophisticated math and ecology behind the author’s work, and the explanation is clear for ecosysems that vary within a range that’s compatible with the requirements of life for specific organisms. Isn’t the argument all about human-induced changes that may be large enough to disrupt those requirements?

    • Part of the difficulty this writer is having is that he is using “tipping points” in a vague and general way to mean just a large change. Yes, large changes do happen, and if we confine our discussion to that term, our ability to think about what may be happening to the environment will improve. “Tipping points” is being used to mean an abrupt, sudden shift from one set of conditions to another, far different set of conditions, not just to refer to a range limit or just to any change. If you would read an article in the March 27, 2009 edition of Science magazine (Richard Kerr “Arctic Summer Sea Ice Could Vanish Soon But Not Suddenly.” Science 323: 1655.), you can see the difference. That article states that a review of the forecasts by a number of global climate model leads to a projection that “summer ice will most likely disappear around 2037. But none of the select models predicts a tipping point—a sudden jump to an ice-free summer.”

      Saying that something is going to undergo a “tipping point” makes things sound much worse than simply saying that things are going to change, and the use taints a discussion in a way that is unscientific and inappropriate in scientific papers about natural ecological systems, and leads us away from, rather than toward, better understanding.

      Also, the term “tipping point” is used in a more specific way to mean a sudden shift from one steady-state to some other state-steady condition of the entire system. Since populations, species, ecosystems, and the entire biosphere are non-steady-state systems, this way of thinking just doesn’t fit. Non-steady-state systems are always changing and do not have neat, specific fixed conditions.

      People who had difficulty with what I have written about tipping points here, where I have to be very brief, would be best helped if they take the time to read my book Discordant Harmonies, where I took the time, and much effort, to explain the nature of nature as best understood by modern science, and to explore the history of the idea, especially the idea of nature in steady state. These ideas are not the easiest or simplest, and can’t be explained in a slogan or phrase. But if we really want to solve environmental problems, we have to understand how nature really works, and that takes time and effort. The term “tipping points” is being used in a way that suggests the answers are simple, which they are not.

      Other essays on my website pursue these ideas in other ways, and could help those of you who are having trouble understanding the concepts.

      Over the next weeks, I will be adding more material to this website to go deeper into the ideas and expand upon them. I hope readers like this one will join me in that pursuit. I’ve spent 4 decades trying to understand nature and help solve environmental problems, and I can tell you that the path is difficult, but fascinating, and also important.

      Dan Botkin

  2. deep solar minimum
    http://science.nasa.gov/headlines/y2009/01apr_deepsolarminimum.htm
    A 50-year low in solar wind pressure:
    A 55-year low in solar radio emissions:
    A 12-year low in solar “irradiance”:

  3. Blah, blah…so should we just take our chances with the environment while continuing to ignore the obvious benefits of investing in “clean”, renewable energy? I’m having my home weatherized and installing a solar hot water heating system to provide domestic hot water and hot water for space heating purposes. When it’s all said and done, I suspect that the reduction in electricity usage will be significant – perhaps as much as 30%-40%. Weatherizing -insulating the attic/crawlspace, caulking/weatherstripping windows and doors – will probably save us another 30% since most of our consumption is a result of lost heat due to a combination of poor insulation and air infiltration. This system will pay for itself in a matter of 3 years or so, and a 30% federal tax credit + state-specific incentives/rebates make installation very affordable, particularly when paid for as part of an EEM (Energy-Efficient Mortgage) or FHA backed home improvement loan.
    I’m fortunate in having a south-facing, unshaded roof that’s ideal for a solar hot water heating system. I don’t see why people are complacent in relying on a bunch of polluting, price-gouging energy monopolies to keep them from freezing/having a heatstroke when all the heat/electricity we need can be generated from those rays of sunshine beating down on our rooftops! We ought to be marching in the streets, demanding an end to the environmental and economic injustices we’ve become party to. There used to be a time when we weren’t surrounded with petroleum by-products, we didn’t have to worry about the air or water being polluted with industrial wastes, and we didn’t have people trying to tell us that the waste was somehow GOOD for us (just not good for plants or wildlife, as if we are somehow so fundamentally different than the rest of the animal kingdom as to be unaffected by something that is very clearly POISONOUS).

    There’s no excuse why every south-facing, unshaded structure shouldn’t be sporting some kind of solar collector(s). We have the technology, and we have the means to mass-produce and install it. So it makes other energy sources obsolete, who cares? Either the energy monopolies need to get on board with renewable, CLEAN energy or they go out of business. Isn’t that how the free market is supposed to work?

  4. I agree that it is all too common to interpret environmental change in the context of multiple stable states. Something that does not bounce back within our scientific attention span is deemed to have transitioned to a new stable regime. Your example of the gradual loss of sea ice is a good one — no sudden switch required.

    What I am confused about is why you seem to insist that bifurcations are inconsistent with constantly changing systems? It is well known that systems exhibiting complex, sometimes unstable oscillations are capable of rapid unpredictable shifts. (Depending on the situation, the switching can be between attractors and in other circumstances a bifurcation occurring when a driver is gradually changed.) There seems to be little confusion about this among mathematical modelers.

    I encountered your site indirectly via your WSJ article. I found that piece frankly muddled and bit misleading (although I think I’m getting a clearer idea of where you’re coming from after reading some of this site). The analogy between “balance of nature” and current climate models seems misplaced. What specifically are you proposing as an alternative to current modeling approaches?

    • To Tim.
      Nothing I wrote was intended to suggest that system could not undergo bifurcations. However, some of what you are writing about refers to compariatvely abstract and theoretical systems. My own experience has focused on the dynamics of ecological systems, and it is less clear for these, with the current state of knowledge, the extent to which unstable oscillations can and are likely to lead to rapid shifts. Whether one wants to call them “unpredictable” when they arise from specific mathematical formulations goes beyond what I could discuss in a short op-ed piece, or even briefly on this website, but it is a topic that deserves considerable study.

Trackbacks

  1. […] But what tipping points are well established and which ones remain what Stephen W. Pacala of Princeton University has called “the monsters behind the door”? I have a piece in the Week in Review section exploring these concerns. Given the limits on space in print, I thought it worthwhile to add some additional voices here and encourage further discussion. The bottom line? A growing effort to clarify such risks has yielded what amounts to the same message climate experts have been conveying for more than two decades: More emissions of greenhouse gases raise the odds of trouble. The conclusion is similar to that in the “burning embers” diagrams from the third Intergovernmental Panel on Climate Change report and a recent paper. [UPDATE, 3/31: Daniel Botkin, the ecologist and author, has weighed in with an exploration of tipping points in ecosystems.] […]

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