There is a chance that the oceans could soon become a quieter place for whales.
The International Maritime Organization (IMO) has just adopted guidelines for the reduction of underwater noise from commercial shipping. The IMO’s Marine Environment Protection Committee has been considering the issue since 2008 when it first put reducing underwater noise pollution from shipping on the agenda following a proposal from the USA.
Over the six year period, the USA has continued to support work on this issue including chairing a correspondence group tasked with developing the guidelines. This work was greatly helped by the enthusiasm of one person, Lindy Johnson, who tragically died before witnessing it coming to fruition.
IFAW is an observer at IMO with particular expertise in marine mammal conservation issues. In 2008, IFAW documented the threats from underwater noise pollution in a report. IFAW also helped the initial work of the correspondence group by contracting Dr Martin Renilson who is a naval architect to prepare a report on reducing underwater noise pollution from commercial ships. The report provided some simple measures for decreasing shipping noise associated with steps that could also increase fuel efficiency and suggested that implementing these measures could also be cost effective in the long term.
After all, noise is wasted energy.
IFAW has continued to fund work on the issue, allowing IFAW consultants to present new results at key international conferences and in published papers so that naval architects, ship designers and ship builders become aware of the adverse effects of shipping noise and what can be done to improve the situation.
The IMO recognised the “degree of scientific uncertainty regarding the exact nature, magnitude, and significance of shipping noise impacts on various marine animals”. But to its credit nevertheless it decided that the evidence was sufficiently strong to take action and reduce shipping noise.
Noise can mask the sounds that whales and dolphins make in order to communicate or feed and it can dramatically decrease the distance over which some animals such as large baleen whales can hear each other. Stress is another way that noise can affect whales. In the days following 9/11 there was a dramatic reduction in ship traffic in the Bay of Fundy, Canada, with a corresponding reduction of noise. Researchers studying North Atlantic right whales over this period measured a reduction in stress hormones associated with a reduction in noise.
Specialised military and oceanographic ships are the quietest in the sea and a great deal of effort has been put into making these already quiet vessels a tiny bit quieter. But very little effort has been put into addressing noise pollution from the 10% of noisiest ships which we think are responsible for about half of the total acoustic footprint from shipping.
The IMO guidelines provide some practical measures to reduce shipping noise, starting with the propeller, which is the main source of underwater noise. Cavitation, which is the formation of vapour bubbles, is the biggest source of noise. Good propeller maintenance and wake flow design (to make the water flow without turbulence) around the stern of the hull help to reduce this source of noise. All this is easier to design into new builds, but some measures can be implemented for existing ships: once again reducing cavitation is key and good propeller design and maintenance helps to do this. For most ships, going slower also substantially reduces noise. In the last few years many ship operators have implemented ‘slow steaming’ to reduce fuel costs by travelling slower. One of the world’s largest shipping companies, Maersk, has taken this further by building ships specially designed to go slower. Continued slow steaming benefits whales through both reduced noise and lower collision risk.
The next stage is for the measures in the guidelines to be implemented both for existing ships and taken into consideration during the construction of new vessels.
In addition, we now need states to implement an earlier IMO decision and use detailed noise measurements to identify the noisiest ships in their fleets so that these can be prioritised for applying technologies to reduce noise.
By encouraging continued slow steaming and implementation of the IMO guidelines we will begin to address the problem of shipping noise.
For more information about IFAW efforts to protect marine mammals, visit our campaign page.
Article source: IFAW