The point of no return

Posted on January 22, 2012 by

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Summary: Tipping points are when systems suddenly change very quickly to another state. In ecosystems this can be catastrophic, with examples including suddenly increasing rates of forest loss or climatic warming. Veraart et al.’s (2011) research, published in Nature, allows us to be aware of whether tipping points are being approached by monitoring how quickly the system recovers from stress, with a slowing rate meaning the tipping point is nearer. This allows better management of biological, social and economic systems.

After passing it's tipping point, the leaning tower of pizza will change from it's erect to horizontal state. Image from Uncyclopedia.

In Nature (the top scientific journal) recently Veraart et al. (2011) published about thresholds and tipping points, and how to tell when one is getting close.

A tipping point is when a system (e.g. an ecosystem, a social system, or any other thing you want to attach ‘system’ to) changes in a big way very suddenly, and it’s really hard or impossible to go back. The analogy is something balanced – e.g. a tower, such as the leaning tower of pizza (figured) – which reaches a point when it falls over. The most topical tipping point is probably to do with global warming. When the Earth heats up, it may reach a point when it suddenly heats up very quickly, in part due to things like methane deposits in the oceans suddenly melting.

Basically, the article says that you can tell when you’re getting near the tipping point by the fact that the system takes longer and longer to respond to ‘perturbation’ – i.e. messing it up. This is important, because it might allow us to see when ecosystems are near their tipping points, and stop them tipping before it’s too late.

The research was done in cyanobacteria, or blue-green algae. This is pretty boring in a way – there are no pandas or people involved – but on the other hand it makes the experiment very neat and easy to do. Pandas might have taken 500 years (if they weren’t extinct before the end of the experiment). They look at light levels, and what happens when the tipping point of too much light is reached.

So what does this mean?

Well, an example of where this could be applied in real life comes from Cury et al. (2011) in Science (the second best scientific journal) recently. Some other researchers looked at seabirds and their eating habits and found a threshold – i.e. a tipping point – of food availability (i.e. fish ‘levels’) below which seabird populations collapse. This point is when prey (i.e. fish and shrimp) biomass (i.e. amount) is 1/3 of the maximum biomass that can exist in that habitat (i.e. ocean). Now, as the authors actually calculated the tipping point, I suppose that kind of lessens the need to have early warning of tipping points in seabirds as we already know what the point is. However in most other kinds of animal we don’t know what this level is, and having early warning of impending disaster is handy.

Other examples of tipping points in nature are when/if the Amazon rainforest might dry up and become a desert. Or when amphibians are suddenly more affected than before by habitat loss, climate change etc. One year (or decade) they might seem OK-ish, the next they all disappear because the tipping point has been reached. If we had seen increasingly slow recovery from environmental damage, the tipping point might have been able to have been avoided.

Finally, these kind of dynamics apply to all ‘systems’ (those of you who did the Systems Analysis course at Uppsala or anything similar will know what I mean by that!). So social systems also have tipping points. A political revolution is what happens when that point is exceeded. So, though it doesn’t solve anything in itself, this is certainly a useful piece of research for all disciplines.

Further reading

Veraart A et al. (2011) Recovery rates reflect distance to a tipping point in a living system. doi:10.1038/nature10723. Read abstract (or full article via an academic institution) at: http://www.nature.com/nature/journal/vaop/ncurrent/full/nature10723.html#/affil-auth

Cury et al. (2011) Global seabird response to forage fish depletion—one-third for the birds. doi:10.1126/science.1212928. Read abstract (or full article via an academic institution) at:

http://www.sciencemag.org/content/334/6063/1703.abstract

Climatic tipping points on Wikipedia:

http://en.wikipedia.org/wiki/Tipping_point_(climatology)


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