Whales in the oceans' ecosystems. (Click to enlarge, and for source.)

If all the whales are gone, it will have a cascade effect. We can say goodbye to entire ecosystems of ocean life.

Back in March 2007, science journalist Scott LaFee of the San Diego Union-Tribune wrote a great article about the role of the great whales in marine ecosystems:

“The fact is, we just don't know very damn much about them,” said Jim Estes, a U.S. Geological Survey research scientist based at UC Santa Cruz. “I think the implicit view has historically been that whales were just these magnificent, big creatures. Nobody asked the question of what that really meant, whether whales were major players in ocean ecosystems.”

In 2003, Estes and colleagues organized an unprecedented scientific symposium to address some of these questions, most notably: Does size really matter? If the great whales were to disappear – a real possibility for some species – what would happen to the world's oceans and remaining inhabitants? “Whales, Whaling and Ocean Ecosystems,” a collection of papers inspired by the symposium, has just been published by the University of California Press.

Estes says that this complex problem can be approached from the point of view of whales (including orcas) as predators, prey, and carcasses.

I talked about how whale carcasses can support entire marine communities in a post on whales and biodiversity; basically, industrial whaling has resulted in less carcasses ending up on the ocean floor.

But LaFee's article covers the other two areas quite well. Regarding whales as prey, Estes and his colleagues describe the situation as "top-down", instead of being driven by food sources at the bottom of the food chain:

In the case of great whales, this ["bottom-up"] thinking might not necessarily hold true. Estes and others have proposed that the much-noted declines of sea otters and pinnepeds like the Steller sea lion may be linked to increased predation by killer whales, which began eating the smaller marine mammals after commercial hunting dramatically reduced the numbers of their old prey, the great whales.

This dietary shift, in turn, provoked a cascade of ecological consequences, the researchers contend. With fewer otters to eat them, for example, sea urchins burgeoned in number and eventually overwhelmed kelp forests. Whole local ecosystems collapsed.

As for whales as predators, wait! Hold on! I know you're going to say "but whales eat too many fish!" Ok, I'll just refer you to this link and say "no, they don't" (and fellow Defending Whales blogger Andrew has a post about that, in fact).

It's not that simple. LaFee's article includes an interesting analogy:

Jackson [a marine researcher] and others draw this analogy: Whales were – and are – like bison, whose astounding pre-19th-century numbers (up to 60 million) significantly shaped the nature of the Great Plains.

“Bison urine was a fertilizer that kept the prairies productive,” writes Peter Kareiva of the Nature Conservancy. “Bison wallows harbored their own unique plant communities, which were in turn favored by American antelope and other large herbivores.”

Surely, the scientists argue, the one-time multitudes of great whales exerted a similar ecological influence on their environment. The exact nature of those contributions is only now coming into focus, example by example.

They say hindsight is 20-20. I hope we aren't saying that 20, 50, 100 years from now, because the whales are all gone, and we see a profound and devastating effect on other creatures in the ocean. I hope we aren't saying "we should have seen this coming".

I hope we're saying "back in 2007, we finally ended commercial whaling, and that's why whales aren't just pictures in books".

Hey, what's wrong with a little optimism?