The Obama administration has decided to reopen the eastern seaboard of the United States to offshore oil and gas exploration, the Guardian has reported (see full report here). This will entail ‘seismic surveys using sonic cannons that pinpoint energy deposits deep beneath the ocean’, through trawling a sonic cannon behind survey ships for up to weeks at a time. The Bureau of Ocean Energy Management ‘acknowledged that thousands of sea creatures will be harmed’, the Guardian reports, but is willing to press ahead with exploration that could generate $195bn for the US economy. The cumulative effects of such exposure on marine mammals and fish are largely unknown, but the problems that sustained exposure to sonic cannons would cause are both behavioural and physiological, with it most likely that the ambient noise created by the sonic cannons will reduce marine mammals’ ability to communicate effectively, echolocate, and perceive prey and predators.
The changes in behaviour that sustained exposure to sonic cannons would cause are thought to have negligible impact, as Acoustic Ecology reports, as they would most likely force sea creatures to move away from the noise. The impact that this kind of “avoidance” behaviour would have on sea mammals, turtles, and fish is not yet clear, as moving away from familiar territory may have a long term affect on reproduction or species survival, through ‘stress, use of limited energy reserves, or temporary exclusion from preferred feeding grounds’. The question becomes one of ethics, and whether it is ethical to impose levels of noise on creatures in such a way that it impairs their lives. In the case of fish or whales, which are either declining or returning from the brink of extinction, noise such as that from sonic cannons may have significant affects on long-term population trends. The uncertainty in knowledge regarding fish stocks and population recovery in cetaceans, is cause surely for caution, and either limiting or precluding the use of sonic cannons would be more beneficial, rather than wait for conclusive evidence .
Acoustic Ecology notes that current mitigation measures include ‘shutting down sonic cannons when cetaceans are seen at very close range, gradually ramping up the power of the cannons over a 15 minute period to allow fish and whales to move away, and employing on-board observers to watch for whales at the surface’. Whilst these mitigations might be in place, little is known about the acoustic perceptual systems of sea creatures, and the impact of human noise upon them, meaning that greater caution should be heeded. Errors that are made now could lead to ‘biologically critical population stresses, including limited genetic diversity or extinction’, and the rush of the Obama administration to move towards opening up the eastern seaboard of the United States could be a rash move indeed.
It is interesting to note that parts of the Pacific Ocean will be receiving protection from the United States (and the Leonardo di Caprio foundation), as can be seen in this video from the New York Times, and it is perhaps naive to imagine that the Atlantic Ocean would also come in for similar protection, certainly once oil is involved.