Underwater noise pollution from ships poses a serious threat to whales and dolphins. So it’s great that the International Maritime Organization (IMO) is now developing guidelines to reduce the levels of underwater noise created by new and existing ships.
You can’t miss the London Headquarters of IMO because there’s a big ship sticking out of the building. The IMO is a United Nations agency with responsibility for safety of shipping and prevention of marine pollution amongst other things.
The organization has 170 government members, and the International Fund For Animal Welfare (IFAW) is accredited as a Non-Governmental Organisation because of our expertise on marine mammals.
I attended a recent meeting of IMO’s Design and Equipment Subcommittee and participated in a drafting group, actively supported by the USA, where guidelines to reduce shipping noise were discussed in some detail.
Although it will be another year before the document is finalised and made public, the text was largely agreed to during our week-long discussions.
Shipping noise can affect the ability of whales to communicate, navigate and find each other to mate. “Shipping noise is very much like having an
industrial size fan on all the time in your house”, was how Dr Mark Baumgartner described it to the February 2013 meeting of the American Association for the Advancement of Science (AAAS). And ship noise is now known to increase levels of stress hormones in right whales.
So what can be done?
An IFAW Report written by Martin Renilson identifies propeller cavitation as the main source of noise.
Simply put, cavitation is the formation and then implosion of water vapour pockets which are caused by pressure changes across the propeller blade. Good propeller design and a smooth wake flow at the stern of the ship are the two design features that can reduce cavitation.
For most ships, the slower they go, the less noise they produce. This brings other benefits such as reducing the fuel consumption (therefore greenhouse gases) and increasing the safety for other users of the sea (including whales) who are at risk of collision.
IFAW believes these simple noise quietening measures will provide the most benefit and will pay for themselves over time in reduced fuel consumption.
After that, the conversation rapidly gets very technical, and the question for any noise quietening measure is one of feasibility and how much will it cost to implement.
Given the evidence presented at the AAAS meeting noting ocean noise has doubled every 10 years over the last 30 years, it’s great the IMO is now addressing the problem.