Air Date: Week of May 19, 1995
Two separate teams of oceanographers have recently published similar findings; over the last sixty years the surface temperature of the ocean off the California coast has risen measurably and more warm water marine species have appeared. The researchers have also found that some cold water marine life has disappeared, and there are fewer species overall. Matt Binder explains.
CURWOOD: This is Living on Earth. I'm Steve Curwood. Off the coast of California, cold water species are disappearing, and warm water species are moving in. Two California scientific teams link the changes to small increases in the surface temperature of the Pacific, and they say the shift has led to an overall decline in marine life. These studies do not prove or disprove the theory that human activity is warming up the Earth. But the research does show that such warming could lead to rapid and devastating changes to ocean life. Matt Binder has our story.
BINDER: The 2 reports published in the journal Science are based on long-term studies of the California coast by 2 distinguished oceanographers nearing the ends of their careers. In San Diego, John McGowan of the Scripps Institute of Oceanography has been coming to this pier 5 times a year for the last 42 years to board a research vessel and make an identical, 500-mile zigzag voyage across the open ocean. At a dozen points along the way the ship stops and the crew lowers a small mesh bucket down 500 feet, and scoops up all the tiny creatures in its path. They also take water samples from varying depths. It is by far the longest running open ocean ecological survey anywhere in the world.
McGOWAN: Basically, what we found was, there's been a very large-scale decline in the abundance of plankton, animal plankton, called zooplankton, over this 42-year period. And furthermore, during that period of decline of plankton, the temperature, the average temperature of the upper layers of the California current has increased by somewhere between 1 and 2 degrees Fahrenheit.
BINDER: The decline in plankton has reached a staggering 70% now, in what was once one of the richest marine environments in the world. And the plankton collapse has had a ripple effect, lowering the number of birds, fish, and sea mammals as well. McGowan fondly recalls his earlier voyages, when the crew would count over 100,000 members of a single bird species, the sooty shearwater, on a typical trip.
McGOWAN: Well, back in the 50s, of course, it was perfectly evident how rich the California current was. We not only saw a lot of birds but a lot of marine mammals and, at night when we stopped the ship and lit lights, there were, the night lighting was very good. The fish aggregated all around, congregated all around the ship. That's no longer true.
BINDER: McGowan says it was the strength of the California current that made this area so rich. He explains that the stronger an ocean current is, the more upwelling it causes, and the upwelling brings crucial nutrients to the surface that plankton need in order to thrive. And it's the plankton that form the basis of the open ocean food chain. McGowan says the small temperature rise in the North Pacific over the last 50 years somehow seems to have slowed down the California current, and reduced the ocean's productivity. But he doesn't know exactly why that's happened.
McGOWAN: I am uncertain as to which cause, man versus nature, is responsible here. What I really think ought to be done, however, is intensify our, this kind of research, not only in the California current but a number of other places. This is an early warning signal and we certainly must pursue it.
(Running water. Chuck Baxter: "This is the study site here. We have a number of harbor seals laying on the rocks now, where they haul out, enjoy the day time. But our...")
BINDER: 400 miles up the coast at Monterey, Chuck Baxter has found a similar dramatic change in his study zone, which is much more conveniently located just a few steps from his office at Stanford University's Hopkins Marine Station. After 40 years of studying the California coast and 20 years of working at Hopkins, Baxter noticed a gradual change in the seaweeds growing in the tidepools just outside his office window. So he decided to investigate, and found that 60 years ago a graduate student did a species by species count of invertebrates in the same tide pool in one of the first such ecosystem surveys ever conducted. Baxter decided to repeat the laborious count, and he found that indeed, the relative numbers of species had changed significantly. Now there are many more southern species in the tidepools, and many fewer northern species. Baxter believes this is linked to the small, 1.3 degree water temperature rise at Hopkins since 1933.
BAXTER: We don't look upon this as being a necessarily direct response to temperature as if northern species were keeling over and dropping dead or anything. It may simply alter competitive advantages. It may do something with part of the life cycle, and have to do with larval transport, or recruitment. There's many ways that climate change can affect organisms.
BINDER: While John McGowan in San Diego is not sure what's causing the small but steady temperature rise in the North Pacific, Charles Baxter says he's convinced that humans have something to do with it. But whatever the cause, he says, these 2 reports should lay to rest the notion that the effects of global warming will be unnoticeable or benign.
BAXTER: Here, we have actual evidence that the climate change that has taken place so far in the Hopkins preserve has produced dramatic changes in the structure of communities and that this, then, is a clear signal that if this is happening more generally we can begin to expect many of the predictions of global warming to begin to become far more obvious.
BINDER: Similar long-term studies will be needed to determine whether these kinds of changes are happening more generally, but very little historical data on the oceans is available to compare to present conditions. Both Baxter and McGowan lament that rather than funding new ecological studies, Congress and state governments seem intent on cutting existing ones. For Living on Earth, I'm Matt Binder in Monterey.
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