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Chris Jones Ebbtide Reporter "Even though until recently there was some question as to whether the heat cycle we're seeing is driven by the change in carbon [emissions], it is well recognized now by anyone who looks at the data, and you can basically track it on a decade and annual basis. It's just like everything in science; there is a correlation and there is some level of uncertainty. I mean, things could be happening, you all could be here right now for some other reason and I might just happen to be talking, but it is very likely there is a correlation as to why you are here and I'm here... There are very few things that are 100-percent certain." Thus Dr. George Divoky, research associate of the Institute of Arctic Biology at the University of Alaska Fairbanks, began his presentation last Thursday to a standing room only crowd in the lecture hall of the 2700 building. Entitled "Watching the world melt away: how seabirds are warning us about climate change," the presentation, part of Earth Day observances and sponsored by the SCC Environmental Club, was given with a rapid-fire delivery reflecting both Divoky's enthusiasm as well as the necessity to complete a 90-minute presentation in 60 minutes. Divoky summarized the results of his 30-year study of a particular colony of arctic sea birds, the results of which demonstrate a close correlation between changes in the arctic climate and carbon emissions over the last century.
In July 1972 on a low island (really not much more than a sand bar) 25 miles from Barrow, Alaska, he was surprised to find a small number of nesting Black Guillemots. This was more than a small surprise since Black Guillemots normally nest in the cracks and crannies of rocky shores and there were no such cavities on the windswept gravel surface of this particular island (Cooper Island). Further investigation revealed that the birds were nesting under a few pieces of wood and discarded boxes left over from some post-Korean War explosive experiments conducted by the U.S. Navy in the late 1950s. On a hunch, Divoky found a box and turned it upside down to see if it might become a nesting site. Sure enough, when he returned in August a pair of Guillemots was occupying the impromptu nest site. It soon became clear that what he had found was the ornithological equivalent of a gold mine. By simply turning over boxes a whole breeding colony of birds could be created in an area which was relatively accessible (at least in comparison to the high cliffs of the Aleutians or Pribilofs), and what's more, the guillemots were temperamentally well suited as research subjects. That is to say, they weren't so high strung that handling them in the course of research had any major detrimental effect on either the adults or the chicks. And so, in the last 30 years (with the exception of '74 and '75) Divoky has spent summers recording every aspect of Black Guillemot breeding and nesting. The colony grew rapidly until there were some 200 nesting sites. Bird housing became so tight that many adult birds had to wait years for sites to become vacant. In May 1984 there was a late snow which delayed the entry of the birds into their nests, so Divoky began to look into the historical snowfall records to see at what date the snow had melted each year (which would also be the first day the guillemots could get into their nesting sites). He found that the records in Barrow showed that over the last 30 years snow melt had occurred earlier and earlier each year and that the entry of the birds into their nest sites corroborated this data. Then, in 1988 there was a late August snow which failed to melt for several days. The birds couldn't make it into their nests to feed their chicks and so when the snow finally did melt many chicks were underweight and subsequently fledged in an unhealthy condition. This prompted Divoky to look even further into the climate data to try and determine how many snow-free days there had been on average historically (the guillemots needed 80 days to lay their eggs, incubate, hatch and then fledge their chicks). According to Divoky's own data, snow-free days had been increasing. The historical data had to come from tree rings and the story it told was surprising indeed. It appeared from the tree ring data that Black Guillemots had been breeding on Cooper Island at virtually the first moment in the last 400 years that it would have been possible for them to breed there. Any time prior to the 1970s would not have provided enough snow-free days to allow successful breeding. By the mid 1990s breeding pairs on the island had declined to 115 from a high of 210. The primary food source for the birds was small arctic cod living just under the edge of the pack ice. Throughout the '70s and '80s the ice edge had been right at Cooper Island. The pantry was next door to the nursery. But in the '90s the edge of the pack ice had begun to retreat to the north. At times it was necessary for the birds to fly up to 25 miles each way to bring dinner back to their hungry chicks. The retreat of the ice edge was having a marked effect on the bird population of Cooper Island. In the last five decades total ice volume of the Arctic Pack Ice had decreased by 40 percent. To Divoky it was appearing more and more evident that the guillemot colony was acting as a sort proxy confirmation of climate change. Wondering if there was a way he could link the guillemots even more closely to longer term environmental changes, he collected guillemot feathers from ornithological collections from around the United States and had them tested for an isotope called Delta 13 Carbon. Delta 13 C is a natural and stable isotope of carbon which is preferentially absorbed in some metabolic processes. In the case of the Black Guillemots it can be used to locate the birds' feeding grounds. The more productive biologically an area is (for example, the Bering Sea) the higher the Delta 13 C signature will be in the tissues of predators feeding there. Birds feeding in less productive biosystems (for example the Arctic Ocean) would have less Delta 13 C accumulated in their tissues. When the results of the Delta 13 C tests were plotted against time (some samples were 120 years old) the results were striking. Delta 13 C in the feathers has declined steadily since 1880, indicating that the Black Guillemots have been feeding further and further to the north as the ice edge has receded - a striking 100-year-long corroboration of the effect of carbon emissions on our climate and a remarkable result for nearly 30 years dedication to a single investigation. Divoky left this week to return to Cooper Island for the season. More details of his research can be found at www.cooperisland.org and in the Jan. 6, 2002, New York Times Magazine article, "George Divoyk's Planet," by Darcy Frey. If you'd like to see a guillemot in person, look under the Edgewater Hotel. Pigeon Guillemots, which have only been separated as a species from the Black Guillemots since the last Ice Age, nest there. © 2003 Shoreline Community College™ |
