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Did Eyjafjallajokull Kill the Precautionary Principle?



In mid-April the airports of most major cities in Europe were closed for the better part of a week as a response to the presence of the volcanic ash cloud that spread over Europe as a consequence of the eruption of the Eyjafjallajokull volcano in Iceland. The decision to allow planes to start flying again is sometimes portrayed as being a result of a reduction of the density of ash over European skies. However, this is only a small part of the story. The crucial decision that allowed planes to start flying appears to have been a decision to set a safe level of volcanic ash, something that the International Civil Aviation Organisation (ICAO) did not do until 20 April, several days after its advice had led to the closure of most of European airspace (See:


It might seem incredible to many that the decision to close airports across Europe was made without any reference to a safe level of volcanic ash in the atmosphere. If we do not know what a safe level for flying is then how do we know whether we have crossed it or not? However, this will not surprise those of us who are familiar with the thinking that underpins much contemporary risk management, particularly in Europe. Broadly speaking there are two approaches to risk management that are commonly taken. One approach is to employ ‘cost-benefit analysis’. Under this approach one considers the risks of a particular course of action as well as the potential benefits of that course of action and attempts to weigh these. The course of action evaluated is then compared with alternative courses of action and the one with the most advantageous balance of costs versus benefits is selected. The other approach is to apply the ‘precautionary principle’. There are many different versions of the precautionary principle, however, the guiding idea behind it is that we should be ‘better safe than sorry’. In other words, we are to make decision about whether to bear significant risks or not without giving full consideration to the potential benefits that may result from us bearing those risks, focusing our attention on the potential for harm.


To decide whether or not to close European airspace on the basis of an application of the precautionary principle it was not necessary to determine what the risks of flying due to volcanic ash were, and to then decide whether they exceeded a threshold or not. All that was necessary was to decide that there was some risk of significant harm, and clearly there was some such risk. So it looks like the initial decision to close much of European airspace resulted from an application of the precautionary principle. When the precautionary principle is applied one does not consider the potential benefits of flying. However, after several days the potential benefits of flight became very apparent as millions of people became stranded in this or that place unable to return to work or to return home. Political pressure to factor in the benefits of flight into decision making was applied and, although the ICAO did not explicitly consider benefits, it did decide to set a threshold at which the risk of damage due to volcanic ash was deemed to be acceptable. But this is to implictly accept that benefits must be given due consideration. Why should we accept any risk if we do not stand to possibly benefit from bearing that risk?


The response of regulators to the volcanic ask problem has been a stunning reversal of policy. Precautionary reasoning has been swiftly abandoned for a decision making procedure in which we accept that there is a level of risk that is worth taking in order to reap the benefits of air transport and this seems, effectively, to be a form of cost benefit analysis. Eyjafjallajokull may not have killed the precautionary principle, but it has shown up its lack of connection to reality in a stark and compelling way.

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