Human impact and hope for the southern resident killer whales

There are now 75 southern killer whales (SRKW), ranking among the species at highest risk of extinction. And it doesn't end there, because a new study led by the Oceans Initiative has shown that the risk is also accelerating, with the orca population declining at a rate of about 1% per year

Sooner than we might think, the Southern Resident Killer Whales (SRKW) could vanish. With a current population of just 75, the threat of extinction is not only present but accelerating, declining at a rate of about 1% per year. This alarming trend is highlighted in a study led by the Oceans Initiative.

The precarious situation of the SRKW

The Southern Resident Killer Whales inhabit the waters off the Pacific coast of North America, ranging from California to Alaska. They feed almost exclusively on Chinook salmon (also known as King salmon), sharing their habitat. However, overfishing of these salmon has drastically reduced their prey availability, leading to a catastrophic decline in the SRKW population.

“Our analyses reveal that the population’s recovery potential is lower than previously estimated due to reduced prey availability,” the study authors write. “This primary threat is compounded by other factors, including a low number of female orcas born in recent years and deaths caused by accidental boat collisions.”

Moreover, the Southern Resident orcas are known to be among the most contaminated marine mammals globally, with dangerously high levels of polychlorinated biphenyls (PCBs). These industrial chemical compounds impair animal growth, immune function, and reproductive health.

These molecules have been banned by the Stockholm Convention on Persistent Organic Pollutants (POPs). Yet, their persistence in the marine environment and resistance to metabolic elimination indicate that it will be decades before the habitats can be deemed safe.

Human impact and the path forward

Largely human-induced, protecting this species will require “aggressive actions,” according to the researchers. Efforts should focus on increasing Chinook salmon populations and restoring the orcas’ habitat.

Efforts must also be made to reduce maritime transport noise in the region, as this significantly diminishes the whales’ ability to forage for food. “Budgets, limits, or thresholds for ocean noise that allow killer whales to efficiently hunt scarce prey may need to be considered,”

explain the study’s authors.

But all is not lost. With concerted conservation efforts, the decline could at least be reversed, potentially leading to a recovery rate of 1% per year.

Preventing extinction is still possible but will require greater sacrifices regarding the use of ocean resources, urban development, and land use practices than would have been necessary had the threats been mitigated even a decade earlier, conclude the researchers.

Will we make these efforts?

The study has been published in Communications Earth & Environment.

Source: Communications Earth & Environment

Condividi su Whatsapp Condividi su Linkedin