I started this two-part series with a short post about noisy seas – a different sort of ‘pollution’ that doesn’t get as much attention as the other important changes taking place in the ocean (microplastics, warming temperatures).
It started with a very interesting article from Nature, called The Quest for Quieter Seas, which is published online here.
That post focused on
- Who is making all of that blasted noise?
- Baselining the noise levels
- Starting to look at the effects.
In this post I’ll continue on into the study of effects and potential remedies.
The US National Oceanic and Atmospheric Administration (NOAA) has suggest a rule of thumb that pulses of sound above 160dB can cause marine mammals to actually make significant changes in their behavior, and if the noise is continuous (not pulses), even 120dB can change the behavior of marine mammals. The previous post had a nice reference chart that showed how these levels of noise compare to more familiar sounds, like jet engines.
So – when it comes to these behavior changes, are they temporary inconveniences, or does this possibly cause something more permanently damaging to the ocean ecosystem?
Data on killer whales found off of Canada’s west coast indicates that resident whales spend 18-25% less time feeding when surrounded by boat noise. The population of these whales is about 75 (you read that correctly, under 100), and they are already dealing with a lowered food supply. Noise pollution complicates this problem and perhaps magnifies it. We know from our project management work that risks can interact with each other in a spiraling fashion (for example… lower budget ► less effective contractor ► more errors ► more draw-down from already-low budget). It appears that there are some spiraling effects here as well.
So what can we do about this? Has anyone tried anything to make changes in the causes of ocean noise? The answer, fortunately, is yes. In the shipping lanes off of Vancouver Island, responding to a request by Vancouver’s ECHO (Enhancing Cetacean Habitat and Observation Program), container ships voluntarily slowed their speed to 11 knots from 18 knots. This did add 30 minutes to their journey, but the reduced engine noise was significant, dropping 24% in intensity. This gave the whales a better chance at feeding and helps prevent the reduction of this limited population of orcas. Have a look at the ECHO program’s website here.
How can we implement these sort of changes? We can use the wisdom of Vilfredo Pareto and his 80-20 rule. Studies show that in a modern fleet of 1,500 ships, 50% of the noise came from 15% of the fleet. So yes, the Pareto principle is just that – a principle. Nobody is holding Vilfredo to exactly 80.000% and 20.00000%. In any case, these “Paretoed-out” ships could be targeted, and we can avoid a drastic measure of retrofitting entire fleets with new engines or restricting the speed of a 1000-plus vessel fleets.
Earlier I discussed air guns, used in seismic surveys, often to search for deposits of oil and gas. These air guns can be functionally replaced with underwater vibrators that create much smaller footprints. Engines of ships can be elevated off the ship floor, and redesigned to reduce cavitation (the creation of popping bubbles – which sound innocent but when they pop in huge quantities, this quickly becomes noise pollution.
Cavitation, by the way, is actually a fascinating principle. Watch this short video to learn more.
And here’s the kicker: reducing noise in ocean-going vessels usually goes hand-in-hand with fuel efficiency.
So the conclusion of this story is that there’s a “kill-two-birds-with-one-stone” effect. Or maybe the more appropriate expression would be, “save two mammals with one initiative”.