David Rains Wallace is a naturalist and author of sixteen books. Among them are Beasts of Eden: Walking Whales, Dawn Horses, and Other Enigmas of Mammal Evolution (UC Press, May 2004), A New York Times Notable Book and The Klamath Knot: Explorations of Myth and Evolution (Twentieth Anniversary Edition, UC Press, April 2003), winner of the John Burroughs Medal. In his latest book, Neptune’s Ark: From Ichthyosaurs to Orcas (UC Press, August 2008), Wallace examines the history and evolution of marine life along the Pacific Coast. In his blog below, he shows how diverse the marine life was millions of years ago and still is to this day.
Our Marine Biodiversity: From Deep Time as Well as Deep Water
By David Rains Wallace
In its August 26 issue, the San Francisco Chronicle reported that west coast marine life is undergoing a resurgence. “After three lean years, the ocean off California’s coast this summer is suddenly rich in nutrients and creatures—from microscopic krill to humpback whales—are thriving anew.” Biologists attribute this to a renewed upwelling of cold water from the ocean floor, which brings to the surface the nutrients that coastal wildlife need. This upwelling makes North America’s west coast the biodiversity hotspot that it is, with its flocks of murres, pelicans, and other seabirds; its seals, sea lions, and sea otters; and its recovering whale species.
Yet there is another reason for the coast’s biodiversity that goes deeper than the ocean floor. It is that marine life has been evolving on North America’s western margin virtually since multi-cellular organisms first appeared over 500 million years ago. The Pacific is the oldest ocean, and the west coast is a treasury of fossil marine organisms as well as living ones. My book Neptune’s Ark: From Ichthyosaurs to Orcas tells the story of this extraordinary marine evolution, and the related story of how explorers and scientists discovered it.
Bones found in northern California’s Klamath Mountains show that–when the dinosaurs were just beginning—primitive marine reptiles called thalattosaurs lived here. West Coast mountains also have yielded later fossils of Dinosaur Age marine giants–plesiosaurs, mosasaurs, and ichthyosaurs. The 1870 discovery of toothed, flightless birds that shared west coast waters with those giants revealed a “missing link” between birds and reptiles that gave early support to Darwin’s theories.
During the Age of Mammals, when mastodons roamed inland, even stranger creatures swam offshore. They included desmostylians, mastodon relatives that grazed on seagrass; mollusk-eating marine bears; relatives of today’s manatees (one of which, the 30-foot Steller’s sea cow, survived into the eighteenth century); flightless birds larger than penguins; soaring birds with twenty-foot wingspans; and “sabertooth” salmon over twice the size of today’s largest species. They included the earliest sea lion relative, a creature named Enaliarctos that swam here 25 million years ago. Its descendants evolved into a fantastic array of creatures, some of which resembled today’s walruses, elephant seals, and sea lions, some of which resembled nothing now alive.
Neptune’s Ark offers context and perspective for those who love the coast’s biotic wealth and are justifiably alarmed by civilization’s impacts on it, such as the climate change that may be interfering with nutrient upwelling. Grave as those impacts are, there is also reason for hope in the adaptability and durability that marine life has shown through an almost unimaginably long past.