In the deep cold of a Maine winter, the reality of our warming climate feels counterintuitive. But as scientists remind us, climate change is best understood over the long term.
In fact, an imperiled ocean bird off the Maine coast is trying to tell us the same thing. Since 1988, a population of Leach鈥檚 storm-petrels in the Bay of Fundy has been breeding less and less successfully, and our warming climate is the culprit, according to new research by 乐播传媒 Professor of Biology Don Dearborn and colleagues.
New research suggests a link between the decline of Leach’s storm-petrels and a warming climate. (Don Dearborn)
The findings by Dearborn, Professor of Biology Robert Mauck of Kenyon College, and the late Professor Emeritus of Biology Charles Huntington of Bowdoin College were published in in December.
The researchers discovered that one specific climate variable, , is the 鈥渟ingle most important predictor of the storm-petrels鈥� hatching success.鈥�
鈥淥ur analysis points out both whether any climate variable is involved鈥� in the birds鈥� breeding decline 鈥� the answer is a definitive yes 鈥� 鈥渁nd also what climate variable is the best predictor, and it’s global mean temperature,鈥� Dearborn says.
Then came “the tipping point.”
Since 1955, researchers on Kent Island, home of the Bowdoin Scientific Station, have recorded all sorts of data about the local storm-petrels, including the birds鈥� success at breeding, determined by checking if there鈥檚 a chick in a nest where previously there had been an incubating egg.
Reviewing data from 1955 to 2010, the researchers saw that the petrels鈥� hatching success initially improved with the rise in global mean temperature. Then came 鈥渢he tipping point,鈥� when success stopped improving. 鈥淭hat year was 1988,鈥� they report. Since then, hatching success has declined as temperatures have continued to increase.
A warming climate affects species in myriad ways, and it鈥檚 believed that 鈥渃hanges in food availability and food quality, paralleled by marked changes in fisheries鈥� are causing the birds鈥� decline on Kent Island.
Jacob Freedman 鈥�18 of Chestnut Hill, Mass., checks a Leach鈥檚 storm-petrel breeding burrow for occupancy during fieldwork on Kent Island last Short Term, part of Professor of Biology Don Dearborn鈥檚 avian biology course. (Don Dearborn)
乐播传媒 students in Professor of Biology Don Dearborn鈥檚 avian biology Short Term course head out to do fieldwork on Kent Island in May 2017. (Don Dearborn).
A researcher takes a blood sample from a Leach鈥檚 storm-petrel on Kent Island in July 2016. (Don Dearborn)
A breeding burrow of a Leach's storm-petrel on Kent Island in the Bay of Fundy. (Don Dearborn)
Quite a few climate variables touch Leach鈥檚 storm-petrels, birds that travel great distances within and between breeding seasons. 鈥淭hese birds are in very different places at different times of the year, and even on different days,鈥� Dearborn says. Many variables mean there have been a variety of 鈥渞easonable biological hypotheses鈥� to explain what鈥檚 happening to the birds.
Besides the rise in global temperature, there are regional temperature changes. There鈥檚 the rise in sea surface temperatures, both in the North Atlantic where the birds find food in the summer, and near the equator where they spend the winter. There鈥檚 the temperature in the birds鈥� own burrows, where they incubate eggs.
By building statistical models with different combinations of known climate variables, the researchers found that the global mean temperature, though 鈥渁 single, broad-brush metric,鈥� nevertheless provides the most useful index to capture 鈥渢he complexity faced by these seabirds over a half-century of climate change.鈥�
听“It is the great integrator.”
With global temperatures unlikely to return to their pre-1988 levels, the researchers warn that 鈥渢he future is not bright for this marine vertebrate breeding in the Bay of Fundy.鈥�
Beyond the fate of the storm-petrels, the study underscores the need to think about climate change as a global phenomenon, 鈥渆ven as the local climate changes differently in different places,鈥� Dearborn explains.
Accordingly, 鈥済lobal mean temperature should be a useful predictor for other natural populations around the world, particularly for other species that travel across large spatial scales, as storm-petrels do,鈥� Dearborn says.
As the researchers say in their paper, 鈥淕lobal temperature is an index of an entire planet鈥檚 worth of interactions. It is the great integrator.鈥�
