Mayday Monday – the Cumulative Nature of Threats
Last week we explained that despite protection as an endangered species for the past ten years, the Southern Resident orca population has failed to show signs of long term recovery.
The current amount of federally designated critical habitat only covers the summer home of the Southern Residents, which is why WDC supports expanding their critical habitat to include their coastal range as well. At the time the original (current) critical habitat was set, it was understood that multiple factors contribute to their decline, but it was not entirely clear which threats had the greatest impact preventing recovery. Their exceptionally low population is a result of many factors, starting with the capture industry of the 1960s and 70s, which removed more than a third of their population.
Today, the three primary threats are vessel traffic and boat noise, chemical pollution, and reduced Chinook salmon stocks – their primary source of food. We will discuss each of these separately in the next three weeks, but looking at the big picture, each of these contributes to a cumulative impact. Beyond these main threats, their small population size also makes the Southern Residents incredibly vulnerable to unpredictable environmental events. For example, if an oil spill were to occur in the Salish Sea, these whales would be highly vulnerable to the effects. This is why critical habitat is such an important legal tool: federal agencies must ensure that actions they approve or carry out within critical habitat are unlikely to appreciably harm the species or habitat. Legally acknowledging more of their geographic range as critical habitat is a broad-scale approach to target many different sources of harm at once.
An important comparison can be made with the Northern Resident community in British Columbia to get a sense of the severity of the Southern Residents’ situation. The main difference between the two habitats is human use of the environment. The whales have very similar ecological requirements in terms of diet and habitat, but annual birth and survival rates are depressed for the Southern whales. A Southern Resident female will likely have at least one calf less than her Northern counterpart during her lifetime, which adds up to a much slower population growth rate. Calf mortality is already quite high (about half don’t make it) so additional sources of stress, especially lack of food, have a drastic negative effect on an already delicate balance. Orcas are long-living with low reproductive rates, and the Southern Residents in particular have a small number of reproductive females.
This will not be an easy problem to solve, so a recovery strategy needs to turn around the current decline and ensure growth over decades. Threats to orca recovery are broad, on the scale of ecosystems. We want to expand critical habitat as part of our ecosystem approach to the recovery of these endangered orcas. Critical habitat is one way to adjust policy and will need to be one component of many changes in how we use the marine environment.
Help us expand the Southern Residents’ critical habitat by signing our letter urging NMFS to protect the full extent of their home.
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