maandag 16 april 2012

I can refer to The Cure at the next EAERE conference

Anyone who had a radio in the 1980s should know these lyrics:

Misjudged your limits
Pushed you too far

It neatly describes my paper with Christopher Costello and Michael Springborn that has just been accepted for presentation at this year's EAERE conference in Prague. The general idea of the paper is this: you are doing something you like, and the more intensively you do it the more you like it. There is a danger, however, of going too far, and if you go too far something nasty happens. Your problem is, you don't know how far is too far. Will you stay on the safe side? Will you experiment to find out what 'going too far' actually means? How much will you experiment? When do you stop experimenting? And how does this all depend on what you already know, and the consequences of crossing the line? That is what the paper is about.

You may wonder what this has to do with the economics of ecosystems. There are several examples of ecosystems suddenly collapsing under man-made pressures such as pollution or exploitation. The most well-known example of this is the shallow lake. You can add phosphorus to a clear shallow lake without noticing any effects, until the phosphorus content crosses a line and the lake suddenly turns turbid. This regime shift, as ecologists call it, happens all of a sudden. It is not like your pasta boiling over, where you can turn the gas down to limit the damage when it happens. And it matters economically whether the lake is clear or turbid: swimmers, anglers and divers prefer clear lakes to turbid ones, so you could lose a lot of recreational values. Moreover, reversing the process is expensive: you need to reduce the phosphorus content to a level much lower than the level that triggered the shift to the turbid state. In many cases you also need to fish intensively for species like bream, because bream enhance the turbid state by stirring up the bottom when they look for food. (By the way, Wageningen University's Mister Shallow Lake, Marten Scheffer, used to play in one of the most legendary Dutch folk bands.)

While working on the paper I realised the problem is actually quite general. The captain of the Costa Concordia faced a similar decision: the closer he got to the Giglio shore to make his salute, the more likely he was to run aground. In his case the consequences of "going too far" are huge: at this moment 30 passengers are confirmed dead while two are still missing.

On a lighter note, Robert Smith describes the same problem in those lines quoted above. I take it he spent just a tad too much time in the pub, at least more than he thought his girlfriend would accept. In some relationships this may cost no more than a box of chocolates, but in the song he loses his relationship altogether. At least he got a hit single out of that experience.

1 opmerking:

  1. I was also thinking of a similar problem. Something that you know will happen but you are not sure when; say you know the lake will go turbid so you are thinking about reducing phosphorous, but you don't know when exactly it will go turbid. What should you do?

    I came up with this when I was cycling towards a red light on my bike. Someone had pressed the button for a green so I knew it would turn green. So, I could slow down and try to keep some speed for when the light turned green (it would be easier than stopping and having to get all that speed back again later). But going slow is kinda hard (you wobble), so maybe I should just stop normally and get the speed back. The question is, what is the optimal amount to slow down by?

    It's a pretty poorly formed idea at this stage, but it popped to mind when I was thinking about your maybe it's a relevant extension or another angle to take...

    Congrats on the accepted paper!