The low-hanging fruit of marine conservation

Seawater is tremendously inefficient at transmitting light. Most visible lights gets diffused and filtered after just several tens of meters, making it perhaps useful only to those critters that live nearest to the surface, and still only for communicating with those within a few body lengths. Sound, on the other hand, moves through the ocean much more efficiently, its waves able to traverse hundreds of kilometers of salty water. Perhaps that’s why so many marine species have evolved to rely upon acoustics for communication, foraging, and social grouping. Dolphins use sound waves to echolocate, for example, and the great whales broadcast their songs to others at the farthest reaches of the seas.

There’s just one problem, and it’s a hairless bipedal primate. Most marine animals evolved in an ocean devoid of humans, but humans have gone and turned the ocean into a global shipping network, a military playground, and a recreational paradise. And those activities generate lots of noise, especially in the Northern Hemisphere, and those sounds are just as efficient at propagating through the water as are the sounds that wild animals have come to rely upon for their survival. Anthropogenic noise not only masks natural noises, but can also result in hearing impairment, behavioral changes, and physiological responses in wildlife.

For that reason, marine scientist Rob Williams of the University of St. Andrews’ Sea Mammal Research Unit asks whether marine protected areas (MPAs) ought to consider noise as a factor in habitat management. “Given the potential for underwater noise from shipping to act as a chronic, habitat-level stressor that can affect both individual animals and ecosystem linkages (e.g., via disruption of predator–prey interactions), it makes sense to consider adding ocean noise to the suite of threats mitigated through the application of marine protected areas,” he and his colleagues wrote recently in the journal Marine Pollution Bulletin. That’s especially important if we wish to protect mobile or migratory marine mammals from the sublethal effects of noise.

They focused on marine mammals in part because most conservation efforts over those animals are species-specific, rather than habitat-specific. MPAs have limited ability to protect animals that are only passing through, after all. Still, it’s useful to combine information on the geographic and temporal distribution of marine mammals with geographic information on noisy and relatively quieter areas. Areas that are already quieter and are of importance to marine mammals ought to be identified so they can be protected. Efforts to maintain the status quo are in some ways the “low-hanging fruit” of the conservation world, possibly easier to carry out than efforts to restore habitats or mitigate stressors elsewhere.

Williams and his team focused on ten marine mammal species living off the coast of British Columbia, Canada: Pacific white-sided dolphins, killer whales, harbor and Dall’s porpoises, harbor and northern elephant seals, Steller sea lions, fin whales, humpback whales, and minke whales. These species represent the diversity of marine mammals that use those waters at least part of the year: toothed whales and rorquals, cetaceans and pinnipeds, and so on. Not only did they gather data on their spatial and temporal distribution, but they also rounded up their audiograms, which indicate what frequencies they are sensitive to. They compared that data with information on anthropogenic shipping noise in the area, collected from ships in Canada’s Pacific exclusive economic zone (EEZ).

For fin, humpback, and minke whales, along with Pacific white-sided dolphins, Dall’s porpoises, Steller sea lions, and northern elephant seals, it turned out that the Gwaii Haanas National Marine Conservation Area is already quite important. While little of the NMCA is a fully protected no-take, no-entry MPA, it would still be an important site to implement the management of noise variables. Indeed, “expanding the management objectives of the…NMCA to include acoustic factors in its management plan would be a more efficient (faster) way to protect irreplaceable quiet sites than starting a number of entirely new efforts in a suite of single-species conservation, recovery, and action plans,” the researchers argue.

One problem of course is that noise moves. The MPA could restrict shipping activities, but the wildlife within it could still be affected by noise from outside of it. The researchers don’t offer a good solution for this problem beyond increased stakeholder engagement. Still, there are many ways in which conservation goals can be achieved primarily through maintaining the status quo, in an economically neutral or favorable way for businesses.

Areas that are already quiet and biologically important ought to stay that way. It may seem like an obvious argument to make, but as decades of research in human behavior have revealed, it is easier to reach agreements on difficult matters after taking steps on simpler ones. And if we don’t, the researchers conclude, “we can expect those acoustic sanctuaries or refugia to disappear eventually.” – Jason G. Goldman | 14 October 2015

Source: Williams, R., Erbe, C., Ashe, E., & Clark, C. W. (2015). Quiet(er) marine protected areas. Marine Pollution Bulletin. DOI: 10.1016/j.marpolbul.2015.09.012.

Header image: Steller sea lions near British Columbia, via shutterstock.com

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