Humans Decimated Earth's Largest Animal, But It's Coming Back

Recently, there has been such an intimidating deluge of bad news about the oceans that it's sometimes overwhelming to digest it all. But as much as human activity has offset ocean equilibrium, we are also getting the hang of reversing some of the damage.

Last September, for example, a team led by fisheries scientist Cole Monnahan discovered that California blue whales had bounced back to about 97 percent of their pre-whaling population. The population may have been as low as 500 after being devastated by whalers over the last century, but Monnahan's team estimated about 2,200 roam the east Pacific today.

The study, published in Marine Mammal Science, was a welcome success story in a literal sea of worrisome news about ocean life. Could the California blue whale be the poster child for marine mammal recovery in general?

I asked Monnahan that question over Skype, and his answer was essentially yes and no. He said that while the rebound of the California blue whale is great news, the global story of blue whale recovery is much more complicated.

For one thing, "whales are hard to study," Monnahan told me. "We only know as much as we do about the California blue whale population because they feed 20 or 30 miles off of Los Angeles. It's rare to be able to do an assessment of a population. They are big animals, but it's a big ocean."

To that point, California blue whales are just one of many blue whale populations in the global seas (Monnahan defines "population," as any group of whales that breeds together). Antarctic blue whales live in very remote and unpeopled regions, so it's a lot harder to study their recovery, especially since they were much harder hit by whaling than the California population.

"There's roughly the same number of whales in the southern hemisphere around Antarctica as there are in the eastern Pacific [off California]," Monnahan told me. "But up here they are almost back to 100 percent of their carrying capacity."

"Down there, they are at, I think, just one or two percent," he said. "We're talking decades and decades before they get back up to carrying capacity, which is thought to be 200,000 to 300,000 whales."

All that said, the fact that any blue whale population has been able to recover is worthy of celebration, considering how recently this species—the largest ever to have roamed the Earth—was utterly decimated by the whale trade.

"We didn't start hunting blue whales in a commercial sense until 1905 in the north Pacific," Monnahan told me. "They were too big and fast, and they would sink if you killed them."

"Then the technology advanced," he continued. "They had faster boats, and they came up with a harpoon that would—it's kind of gruesome—go into the body cavity and explode, and pump up the whale like a balloon so it would float."

These kinds of grotesque tools and techniques were par for the course for whalers, Monnahan told me. "I spent a year digging through historical whaling records and it was absolutely disgusting," he said.

Blue whales were finally protected under a 1966 international whaling ban, followed by the 1972 Marine Mammal Protection Act. The MMPA criminalized whaling, and made scientific research into marine mammal recovery mandatory. "We study them extensively in the United States because by law we have to," Monnahan told me.

Along those lines, Monnahan and other researchers will continue to be vigilant in studying blue whales—and other marine mammals—to prevent them from facing extinction again.

"Conservation is really important," he told me. "It's a matter of what we care about as world citizens. The oceans are dynamic and change a lot, and it is very important to keep monitoring this population and updating as time goes on, to make sure that they don't start to decline again."

"We didn't know what to expect [with the 2014 study] but we were proud of it," he added. "It gives people some hope. We did some really bad things, but if we just give them a chance and some space, and don't bother them, then at least some populations can bounce back."

"That makes me personally feel good about the future," Monnahan said. "If we can do the right thing now, the ocean could be at a better state in the future."

Hell or Salt Water is a series on Motherboard about exploring and preserving our oceans. Follow along here.