Scientists studying 60 years in the life of a California tidal zone will report today that whole populations of sea creatures, including snails, crabs, starfish and anemone are migrating northward in reaction to rising ocean temperatures.
While the shifts may have been helped along by a number of factors, including the so-called El Nino effect, the population changes may provide intriguing new evidence of the impact of global warming.
“The fact that creatures who prefer warmer water are now thriving in a place where they were once relatively rare came as a big surprise to us,” said Charles Baxter, one of two scientists at the Monterey Bay Aquarium Research Institute in central California who headed the research project. “What we see is evidence that the effects of global warming may already be apparent, at least in the Northern Hemisphere.”
Baxter and three colleagues published their findings in today’s issue of the journal Science.
There is broad agreement among scientists that the Earth has gotten warmer by at least a degree during the past 100 years. But there is considerable controversy over the impact climate change is having on the Earth. There is also much disagreement whether man-made gases such as carbon dioxide are fueling the increase in temperature.
In the Monterey Bay study, scientists re turned to the exact location of a research project done in the early 1930s which took stock of the creatures inhabiting a 35 squareyard patch of rocks and tide pools.
The new study documented dramatic changes in the dispersion of 16 invertebrate species. In an inch-by-inch inventory, the aquarium’s research team documented significant increases in the population of eight species more commonly found in Southern California, and a decrease in five “northern” species that the 1930s study found in abundance.
The scientists attribute the population shifts to a slow, steady warming trend. Over the past 60 years, according to the scientists, the average shoreline temperature has risen more than 1 degree, while the average maximum water temperature has gone up 4 degrees.
By moving species northward on warm ocean flows, the El Nino phenomenon of unusually warm currents generated in the central Pacific could be a factor in altering the balance of Monterey Bay species. However, the scientists point out that El Nino is a temporary force.
“As a periodic event, El Nino might be able to bring animals north, but it wouldn’t sustain them over a period of many years because temperatures would eventually go down again,” said Rafe Sagarin, one of the researchers who participated in the study.