In a new letter published in the journal Science, my co-author Juan Jose Alava and I question the downlisting of humpback whales on Canada’s Species-At-Risk Act from ‘Threatened’ to a ‘Species of Special Concern’. The decision to downlist humpbacks occurred immediately prior to the federal government’s approval of the Enbridge Northern Gateway pipeline project. The National Energy Board’s decision contained 209 provisions for Enbridge, including conditions related to marine mammals.
If the Northern Gateway pipeline is built – amidst strong opposition from First Nations, scientists, and British Columbians – ocean-going tanker traffic would increase considerably in the humpbacks’ habitat. The official downlisting was significant because the whales’ critical habitat, which overlaps proposed oil tanker routes, does not have to be formally protected under the revised status.
Threats to the whales with increased tanker traffic transcend the danger associated with an oil spill. During the time humpbacks reside in B.C. waters, to feed or migrate through to Alaska, considerable risks are also posed by vessel strikes and persistent underwater noise pollution. The affected humpback whales are part of the larger North Pacific population, once hunted so heavily that a worldwide moratorium was implemented in the 1960s to protect them. Currently, there are an estimated 2,145 humpback whales in B.C., about half of the 4,000 pre-whaling population – although there is uncertainty around these numbers.
The decision to downlist humpbacks in Canada was delayed, as scientists debated whether B.C. humpback whales should be considered one or two management units based on their genetics. A recent study found that humpback whales in Northern B.C. are genetically distinct from those in Southern B.C. waters. Nevertheless, COSEWIC did not split the two units when making their decision to downlist.
Placing humpback whales into distinct ‘stocks’ or ‘units’ is admittedly difficult. Humpbacks have one of the longest migrations of any marine species between their tropical feeding grounds and northerly feeding sites. The whales tend to return to the same breeding site year after year, but mixing may occur as the whales migrate to their feeding grounds (note: breeding occurs in tropical waters, so this mixing is likely not genetic).
However, regardless of scientific debate on biological management units or uncertainty around population estimates, B.C. humpback whales should be designated as a special management unit in the context of risk management. Similar steps to designate a management unit based on risk have been taken in Ecuador, where humpback whales are uniquely threatened by entanglement in specific fishing gear that is not present across the whale’s entire migratory route.
Unfortunately, ‘relisting’ humpback whales should the Northern Gateway project go through would likely be logistically difficult, despite the increased risks associated with oil tanker traffic. We call on the federal government to stand by its responsibility to preserve marine mammals and their habitats.
The original letter in Science can be found here (paywalled). I welcome discussion in the comments below or contact me via e-mail at joshsilberg [at] gmail.com.