Why are so many whales dying on California beaches?

On June 21, a dead gray whale 45 feet long, longer than a city bus, washed up on Ocean Beach on the western border of San Francisco. A day earlier, a fin whale washed up on another beach south of town. In May, seven gray whale carcasses landed on Bay Area beaches. Six more stranded whales were discovered in April.

Each year, gray whales travel the west coast between Mexico and Alaska, a 12,000 mile round trip. In 2019, whale strandings along the coast began to increase (the National Oceanic and Atmospheric Administration refers to them as an “unusual mortality event”). Other whales appear to die further in the water and sink, so the actual death toll is unclear. “We know that for every whale stranded on our shores, ten more whales may die off shore and never be seen,” said Steve Jones, senior media specialist for the oceans program at the nonprofit Center for Biological Diversity. According to one estimate, the total population of the species along the coast fell by more than 7,000 animals, or a quarter of the population, between 2016 and 2020.

Scientists still don’t know why so many whales are dying, but climate change could be part of the problem. “In the Arctic, where they feed, the waters are warming,” says Kathi George, director of field operations and response at the Marine Mammal Center, a Bay Area nonprofit that save injured marine animals. “With the warming of the waters, you will not have such productive waters. So the quantity and quality of the food they eat in the Arctic has not been so high in recent years. The whales began these migrations in poorer health than in years past. “

The whales also began to take unusual detours on their journey. While they usually don’t eat while traveling – force-feed in the Arctic, then travel to Mexico without food – they have started making stops in the Bay Area for more food. Research in Mexico has shown that many whales are now leaner than they should be. “When they are undernourished, they can be more susceptible to human-made impacts,” she says. It has not been possible to determine the cause of death of all of the whales that have stranded on California beaches this year, but many have clearly been struck by ships, which may have occurred while they were foraged near the shore.

Solving the problem of climate change isn’t something that happens quickly – and the Arctic has warmed three times faster than the rest of the planet – but it’s relatively simple to keep ships out. collision with whales. “Science supports a really simple solution,” Jones says. “And those are the mandatory speed limits.”

In April, the Center for Biological Diversity filed a petition with the National Marine Fisheries Service calling for a mandatory 10 knot speed limit for large vessels in whale habitat to protect other even more endangered species, including the endangered blue whale. Whales are more likely to stray from a ship’s path when moving at this speed. The association, which sued the government earlier in the year for failing to comply with the requirements of the endangered species law, also argues that shipping lanes should change and that ships traveling north and the south along the coast should move further offshore to avoid the area where whales are most likely to travel.

Although speed limits are always voluntary, companies that use freighters to transport goods could put pressure on their shipping lines to slow down. Whale Safe, a project in Southern California that uses acoustic monitoring to listen for whales and warn nearby ships, issues score cards to show how well ships are staying within speed limits. “If more companies are using ships that [are] complying with voluntary speed reductions and getting good report cards, that might be helpful, ”says George, noting that the Marine Mammal Center also wants to collect more data on where the whales are and how long they are. remain in the shipping lanes.

Some whales die after becoming entangled in the long ropes attached to crab pots. Newer, cordless crab traps could solve the problem, Jones says, but the industry is reluctant to test them in California. “They don’t want to see any kind of change in the 19th century technology they are using,” he says.

Gray whales have rebounded in the past – the species was hunted almost to extinction in the mid-20th century, but recovered after US laws banned whaling. Now climate change may be a bigger challenge. Understanding what’s going on right now, scientists say, is critical because gray whales are an adaptable species, and if they’re struggling, that’s a signal that the wider ocean ecosystem is in trouble as well.