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According to a new study, the future of more than half of the world's population of killer whales is threatened, in part, by man-made chemicals produced throughout the mid-1900s. in the ocean.
"One important conclusion is that a single chemical class – PCBs – continues to threaten wildlife after production and sale. [has] Peter Ross, co-author of the study and vice-president of research at the non-profit organization Ocean Wise, told ABC News. "This, coupled with the global nature of the threat, highlights the vulnerability of killer whales."
The study found that the combined effects of PCBs on reproduction and immune function in 10 of the 19 whale populations studied could potentially prevent the long-term viability of killer whales. According to the study, these effects were most pronounced among populations living in the waters closest to highly industrialized areas, such as the Strait of Gibraltar, the United Kingdom and the Northeast Pacific.
Based on their findings, orcas face a high risk of population collapse over the next 30 to 40 years, according to the study's authors. According to Ross, the largest declines could occur in the United States, Canada, and parts of Europe and industrialized Asia.
PCBs, or polychlorinated biphenyls, are artificial chemicals used industrially and commercially from 1929 to 1979 – when they have been banned because of their toxicity – in electrical and hydraulic equipment, paints, plastics and plastics. made of rubber. Protection Agency.
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Although banned for decades, PCBs, whose consistency varies from an oily substance to a waxy solid, can infiltrate into the environment through poorly maintained hazardous waste, leakage of machinery and vapors into the atmosphere.
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An important finding is that a single chemical class – PCBs – continues to threaten wildlife after production and sale. [has] stopped.
"Killer whales once thrived in all the world's oceans, but only those in the less-polluted waters of the Arctic and Antarctic seem to be able to support growth," says the study released Friday in the US. Science magazine.
Exposure to PCBs not only affects the fertility and immune function of whales, but also other animals, including polar bears, according to Rune Dietz, a professor in the Department of Biosciences and at the Arctic Research Center's the University of Aarhus. But since female killer whales only live 60 to 70 years and have "very few calves in their lifetime", it is possible that PCBs could "tilt the balance towards the extinction of the local population" said Ross.
Orcas are exposed to such high levels of PCBs partly because of their place in the food chain: they eat other animals containing PCBs in their bodies, which accumulate to dangerous levels.
But PCBs are not the only factor behind the risk of population collapse.
"The availability of food, malnutrition in some populations such as resident killer whales in Canada and the United States have been noted," Ross adds, "in addition to noise, disturbances and contaminants can seal the whales' fate in a changing world ".
It is likely that these combined effects contributed to the recent death of two killer whales. One of them, a southern calf born just 30 minutes before dying in July, was carried for more than two weeks by his grieving mother. The other, a 3 year old southern resident named Scarlet, was last seen with underweight and infections. She had disappeared and was never found.
Anthony Rivas contributed to this report.
