On June 21, a 45-foot-long dead gray whale, longer than a city bus, washed ashore on Ocean Beach on the western border of San Francisco. A day earlier, a fin whale washed up on another beach south of the city. In May, seven gray whale carcasses landed on Bay Area beaches. Six other stranded whales were discovered in April.
Each year, gray whales travel along the West Coast between Mexico and Alaska, a journey as long as 12,000 miles round trip. In 2019, whale strandings along the coast began to surge (the National Oceanic and Atmospheric Administration designates them as an “unusual mortality event”). Other whales seem to be dying farther out in the water and sinking, so the true number of deaths isn’t clear. “We know that for every one whale that washes up on our shores, that another ten whales can die offshore and never be seen,” says Steve Jones, a senior media specialist for the oceans program at the nonprofit Center for Biological Diversity. By one estimate, the total population of the species along the coast dropped 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 may be part of the problem. “In the Arctic, where they are feeding, the waters are warming,” says Kathi George, the director of field operations and response at the Marine Mammal Center, a Bay Area nonprofit that rescues injured marine animals. “With warming waters, you’re not going to have as productive waters. So the quantity and quality of the food that they eat in the Arctic has not been as high in recent years. The whales have been starting these migrations not as healthy as they have in years past.”
The whales have also started taking unusual detours on their trip. While they typically don’t eat while traveling—gorging themselves in the Arctic, and then making it to Mexico without feeding—they have started to make stops in the Bay Area to feed more. Research in Mexico has shown that many whales are now skinnier than they should be. “When they’re malnourished, they may be more susceptible to human-caused impacts,” she says. It hasn’t been possible to determine the cause of death for all the whales that have stranded on California beaches this year, but many were clearly hit by ships, something that may have happened while they were feeding near the shore.
Solving the climate change end of the problem is not something that is happening quickly—and the Arctic has been warming three times faster than the rest of the planet—but it’s relatively simple to prevent ships from colliding with whales. “Science supports a really easy solution,” says Jones. “And that’s mandatory speed limits.”
In April, the Center for Biological Diversity filed a petition to the National Marine Fisheries Service asking for a mandatory 10-knot speed limit for large ships in whale habitat to protect other species that are even more at risk, including the endangered blue whale. Whales have a better chance of being able to swim out of a ship’s path when it’s traveling at that speed. The nonprofit, which sued the government earlier in the year for failing to meet Endangered Species Act requirements, also argues that shipping routes should change, and ships traveling north and south along the coast should move farther offshore to avoid the area where whales are most likely to travel.
While speed limits are still voluntary, companies that use cargo ships to move goods could pressure their shipping companies to slow down. Whale Safe, a project in Southern California that uses acoustic monitoring to listen for whales and warn nearby ships, issues report cards to show how well ships are complying with speed limits. “If more companies utilize ships that [are] complying with the voluntary speed reductions and getting good report cards, that could be helpful,” says George, noting that the Marine Mammal Center also wants to gather more data about where whales are and how long they’re staying in shipping lanes.
Some whales die after getting tangled in the long ropes attached to crab traps. Newer, ropeless 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 sort of changes to the 19th-century technology that they use,” he says.
Gray whales have bounced back in the past—the species was hunted nearly to extinction by the middle of the 20th century but recovered after U.S. laws banned whaling. Now climate change may be a bigger challenge. It’s critical to understand what’s happening now, scientists say, because gray whales are an adaptable species, and if they’re struggling, it’s a signal that the broader ocean ecosystem is also in trouble.