Using bubbles and vibrators to help protect whales from underwater noise pollution
In addition to shipping noise there are two other sources of underwater noise pollution which threaten whales and dolphins. Seismic surveys with blasting airguns are used by the oil and gas industry to prospect for oil in our oceans.
And pile driving with huge hammers in order to build offshore wind farms and other construction projects is also extremely noisy.
With this in mind Sharon Livermore and I attended a recent workshop near Washington DC which looked at ways of making these two activities quieter. We left the workshop thinking that there is clearly a lot that industry can do but if – and only if - regulations are put in place.
Very loud underwater noises can cause injury and death. Or they can cause temporary or permanent deafness. Even at much lower levels, noise can displace whales and dolphins from critical habitat important for their feeding or breeding.
These noise pollution problems are well-understood and there are two ways of dealing with them.
The first approach is to include marine mammal observers or passive acoustic monitoring for marine mammal sounds and to employ some kind of a procedure when marine mammals are detected that limits the amount of noise to which they are exposed.
It makes the regulators feel good.
Unfortunately, no-one has yet calculated what level of risk reduction results from this approach. At night, or in rough weather, whales and dolphins won’t be seen. Nor will animals that are beneath the surface. And inconspicuous animals such as harbour porpoises are very difficult to spot, even in ideal conditions.
The International Fund for Animal Welfare is calling for calculations to be made that show the levels of risk reduction (if any) that result. In the absence of proper science of this kind, some of the mitigation that we are seeing now may just be greenwash.
The second approach is to decrease source levels – in other words, make the activity quieter.
It is obvious this is the better way forward.
With this in mind, the workshop, which was organised by the Bureau of Ocean Energy Management, (a US Government Agency), was on exactly the right subject.
The full title of the workshop was Quieting Technologies for Reducing Noise During Seismic Surveying and Pile Driving. It was well-organised and brought in experts from around the world.
In Australia there is a massive push to exploit offshore oil and gas. Of course the threat of seismic surveying activities is only one part of the problem, but particularly relevant when seismic surveys are carried out in important whale habitat such as the Bonney Upwelling and off Kangaroo Island.
And with the rush to develop offshore wind farms, a massive amount of pile driving is about to be under taken in the North Sea, east of England, where the world’s largest wind farm will be built on the Dogger Bank.
Also at the workshop we learned the oil industry claims it is not yet ready to use quieter technologies such as vibroseis (the use of marine vibration devices instead of air gun explosions). This is despite the fact that such devices have been available for around half a century.
In contrast, in the last couple of years, pile driving technologies have been rapidly adapted to dramatically reduce the amount of noise that results. There are various alternatives, such as using bubble curtains, or coffer dams that exclude water from the area around the pile driving.
What caused this dramatic innovation in the pile driving industry?
In Germany, a noise limit was set at 160dB at 750 metres. What is now needed are for similar limits to be applied to seismic surveying around the world. Only then will we see the oil industry also wake up to the new smart seismic technologies that are already available.