Bright extinction: Scientists have coined this term to describe the situation facing Southern Resident killer whales
Worrying signs of an accelerated decline in Southern Resident killer whales.
In 2015, scientists from the Raincoast Conservation Foundation teamed up with international experts to model the viability of critically endangered Southern Resident killer whales (SRKW) that frequent the coastal waters of the US and Canada. That study (Lacy et al. 2017) found that if conditions didn’t change for the 81 killer whales alive at the time, the population had a 25% chance of functional extinction (numbers too low to recover) within 100 years.
Fast forward eight years to 2023.
With a continued decline in the population to just 75 individuals, a larger team of scientific experts re-assessed the problems facing these killer whales. With updated analyses and the consideration of a broader suite of threats, the team advanced a new term – ‘bright extinction’- that illustrates the conservation stalemate we find ourselves in today.
Bright extinction
Within the planet’s current 6th mass extinction, the term ‘dark extinction’ has been used to describe the loss of species where data are limited and their threats poorly documented. The concept of dark extinction might lead people to think that extinction is largely an information deficit problem, effectively implying that if we only knew that a population or species were facing extinction, we would take steps to mitigate the stressors and halt the decline.
The case of the Southern Residents is in stark contrast with incidents of dark extinction. Southern Residents are, in fact, among the world’s best studied cetacean populations. Not only do we know every individual and their age, but we know the female lineage of every whale. We know what they eat. We know when pregnancies occur and if they are terminated. We know when calves are born and if they die. We can identify whales in poor condition, and predict their death or survival over the ensuing months.
We have equally documented the primary threats facing the SRKW from human activities. Although these threats can be modeled more reliably today, the threats themselves are largely unchanged from those identified 20 years ago when the whales were first listed as endangered in Canada and the US.
Extinction likelihoods
Our updated Population Viability Analysis, published in Nature’s Communications Earth & Environment, tested the sensitivity of Southern Residents to the population’s age structure, survival within age classes, and the role of their Chinook salmon prey to affect survival. Our findings reveal that habitat degradation in the form of underwater noise, continuing high levels of persistent industrial chemicals, and declining quality and quantity of their Chinook salmon prey still inhibit the population from recovery.
Of particular note, we found that the potential for recovery was lower than previously estimated. This means recovery will require more concerted, and potentially costly, conservation actions than had we intervened a decade earlier.
Our baseline model shows that over the next 100 years, the population is projected to decline at a rate of 1% -2% annually. While initially slow, this rate of decline is expected to increase after two generations (~ 40 years), a pattern typical of populations headed towards extinction. Our finding of a lower recovery potential can be attributed to several factors, including fewer breeding females, unnatural mortality like the loss of individual whales to vessel strikes, and potentially heightened effects of inbreeding. Lastly, the role of Chinook to positively influence birth rates is not as strong as it was a decade ago. This may be due to a weakening in the importance of Chinook or a decline in statistical power from the low numbers of annual births.
Can Southern Resident killer whales recover?
These urban whales must find food in busy, noisy, and polluted waters. Although no single scenario can help SRKWs reach the stated US recovery objective (2.3% annual growth rate over 28 years), concerted efforts can halt and reverse the decline, and could even attain a 1% annual rate of recovery. In a population of 75 individuals, a single birth or death represents an annual growth or decline of 1.4%, underscoring the value of maximizing the survival of each individual.
Achieving 1% population growth requires mitigating effects of human activities on individual killer whales and their primary prey. Specifically, such an eleventh hour recovery would require us to get serious about actions to reduce underwater noise, lower the release of harmful contaminants into salmon or whale waterways, and address the way we manage salmon and their habitat.
Chinook salmon as SRKW prey
Recovery actions for Southern Residents have long recognized the need to ensure adequate prey. Our analysis showed that the action with the greatest leverage for SRKW recovery remains their access to Chinook salmon. Although increased Chinook salmon abundance alone did not lead to a full predicted recovery of the SRKW population, all successful mitigation scenarios did include ambitious salmon management.
Increased abundance and quality of prey within SRKW critical habitat doesn’t require producing more hatchery salmon; this can best be realized through changes to fishing practices. Moving Pacific Salmon Treaty fisheries in Alaska and BC away from Chinook rearing grounds and migration routes and into terminal locations near their spawning rivers would lead to an immediate and significant (25%) increase of Chinook salmon in the Critical Habitat of Southern Residents.
Such a transition from marine fisheries to terminal areas can also increase the abundance of the older, larger Chinook salmon that Southern Residents relied on in the early 20th century. An increased size in Chinook would result from stopping the harvest of immature Chinook that occurs in marine fisheries. Further, allowing large females to pass through terminal fisheries to spawning grounds can increase the size of Chinook even further, up to 40% over a 50-year period. Scaling these scenarios to consider both improved value and abundance of mature Chinook salmon in critical habitat results in increases of 35%, 28%, 18%, and 9% at the end of 50 years, if scaled for effectiveness at 100%, 75%, 50%, and 25%. While not quantified in this study, freshwater habitat restoration and protection would further support recovery of wild Chinook.
Underwater noise
Reducing exposure to underwater vessel noise is essential for recovery because such noise interferes with the foraging success of Southern Residents. Mitigating vessel noise requires a range of approaches from building quieter ships to regulating greater distances between vessels and whales, and expanded slowdowns. The slowing of ships can reduce noise energy by nearly half, allowing for more successful foraging activity by killer whales.
While efforts to reduce the problems from existing noise are underway, shipping expansions like Trans Mountain (TMX) in Burnaby and Terminal 2 at Roberts Bank in Tsawwassen will further increase noise. The noise from TMX oil tanker traffic alone effectively erases the benefits that were gained from shipping slowdowns. Raincoast’s 2015 analysis of noise impacts from TMX indicated that the near continuous presence of vessel traffic (all vessels) that would occur from the addition of daily inbound and outbound oil tankers, will reduce the prey intake of killer whales by up to 19%. Developing ocean noise budgets, caps, and limits, that allow killer whales to hunt scarce prey more effectively, are needed.
Contaminants
The inherent vulnerability of killer whales to the accumulation of very high levels of industrial chemicals is now well understood. With long lives – up to 90 years – and a position atop the marine food web, SRKW are prone to the effects of persistent, bioaccumulative, and toxic contaminants including PCBs, DDT, or flame retardants.
While interdictions on the manufacture and sale of some chemicals have resulted in declining levels of many contaminants in killer whales (including PCBs and DDT), new and emerging contaminants threaten both SRKW and salmon. Be it ‘forever chemicals’ (Per-and polyfluoroalkyl substances; PFAS) found recently in killer whales, or the outright deaths of coho salmon attributed to the tire chemical 6-PPD (and its breakdown product), contaminants remain an ongoing concern in the habitat of SRKW and their prey.
Protecting and restoring salmon populations is critical to the recovery of Southern Residents. Land use must be improved to better protect watersheds, riparian zones, and salmon waterways. Municipal and regional authorities must address the release of harmful contaminants through stormwater discharge. The performance of municipal and industrial wastewater discharges should take into account the vulnerabilities of killer whales and their prey in both freshwater and marine environments. Green infrastructure options are a practical way to stem the release of harmful tire chemicals, microplastics, hydrocarbons, metals, and other contaminants into fish habitat.
The path ahead
In a declining population, the greater the lag time between knowledge and mitigation, the more draconian the actions necessary for recovery become. Delaying mitigation also increases the economic and social costs of those actions and increases the risk that threat reduction efforts will not work.
Unfortunately, the listing of species under endangered species legislation alone is insufficient to ensure survival and recovery of endangered species. In the face of ‘bright extinction’, targeted threat reduction measures, in addition to community involvement, are needed to reverse the decline and set the SRKW on a path to recovery.
Southern Resident killer whales keep reminding us about the need for a true ecosystem approach that seamlessly addresses each and every threat.
You can help
Raincoast’s in-house scientists, collaborating graduate students, postdoctoral fellows, and professors make us unique among conservation groups. We work with First Nations, academic institutions, government, and other NGOs to build support and inform decisions that protect aquatic and terrestrial ecosystems, and the wildlife that depend on them. We conduct ethically applied, process-oriented, and hypothesis-driven research that has immediate and relevant utility for conservation deliberations and the collective body of scientific knowledge.
We investigate to understand coastal species and processes. We inform by bringing science to decision-makers and communities. We inspire action to protect wildlife and wildlife habitats.
