Evidence of global warming is all around us
BY PETER B. BRACE
Fourth in a Series

Poison ivy on a carbon dioxide binge engulfing the island in an itchy thicket is certainly a vegetative scourge Nantucket can manage.

Its oily red-green, three-leaf clustered vines can simply be removed as needed.

What cannot be so easily undone is the short-circuiting of historical bird migration patterns and simultaneous range expansion and habitat loss, the warming, rising and acidification of our oceans, and all the related consequences, including the re-shaping of Nantucket's shoreline.

As climate change envelops our planet, here on Nantucket, you may have noticed subtle changes in the island's natural world. Or you are wondering what all the fuss is about because you have not noticed anything unusual other than the typically quirky New England weather.

Shifting seasons, including a prolonged rainy, cold spring that can have dire consequences for such creatures as hungry honeybees that need to get out of their hives to find the year's first flowers for nectar to pad their larders, and ospreys, which require an abundant supply of fish to feed their young. Warmer summers, autumns and winters coaxing some migratory birds to extend their stays. Harbor water temperatures in the winter that do not dip low enough for shellfish to go into hibernation.

Visible or not, climate change is affecting the island. These are likely some of the signs of our changing island climate.

THE BIRDS...

Nantucket is a bustling crossroads of bird species - a way station for scores of migrating birds headed up and down the coast and, for some, a new home because of warmer temperatures or shrinking habitat at the other end of their migration routes.

"Some of the birds that migrate through here spend their breeding season in the boreal forests, [but] four species of trees are being affected by the spruce bud worm that is eating them," island bird expert Ken Blackshaw said of the evergreen tree species in Eurasia where these birds live. "They're becoming a casualty of global warming. Things like the rusty blackbird, Canada and bay-breasted warblers and the olive-sided flycatcher."

Blackshaw said the golden-eye duck is late in getting to Nantucket.

"Many of the birds that would normally be here in the winter just haven't arrived here yet," he said. "The golden-eye just got here because it's been so temperate up there [coastal Maine]."

During the most recent Christmas Bird Count on Dec. 30, bird counters noted fish crows, which are a southern species, for the first time on Nantucket.

Fellow Nantucket bird expert Edie Ray said that fish crows are breeding on Cape Cod now and may have spread to Nantucket because West Nile virus took a large bite out of American crow populations on the Cape and Islands. Fewer American crows, which are larger than the fish crow, means more food is available for the fish crows,

"I definitely think we're looking at more changes in what kinds of birds we're seeing here on Nantucket, like turkey vultures. Five or six years ago, to see one here in the winter would be unusual, and now we expect to see them," said Ray. "Redbellied woodpeckers are a southern species and now we see them here year-round."

Ray also cited another southern bird species, American oystercatchers, as having expanded its northern range to include Nantucket.

Though not specifically tied to global warming but probably more to climate change, the spring of 2005 was especially cold and rainy during May, June and early July, causing the harbor waters to warm up slower than normal and consequently, fish spawning to suffer. The lack of fish prevented ospreys on the eastern half of the island from finding enough food to feed their chicks. As a result, nine of 11 osprey chicks that hatched on the eastern side of the island died that year.

...AND THE BEES

Not all winged creatures migrate to and from Nantucket. Honeybees, which spend their winters in hives, in tree trunks or buildings, live and die by the seasons and, while adaptable to fluctuations in weather patterns, the bees' numbers could suffer if prolonged rainy weather takes over the Nantucket spring.

Jim Gross, the godfather of beekeepers on Nantucket, remains skeptical of climate change impacts on his bees, but he hinted at some potential effects of global warming.

"If we have a lot of rain and it's cold, and we have bees in the hive, then you have a swarm potential," he said. "In the springtime the queen is laying 1,200 to 1,500 eggs a day, so she's an egg-laying machine and while she's doing this, she'll fill up all the larval cells in the hive and the foragers are out bringing in nectar and pollen and they're filling up cells in the hive and when they run out of space, that triggers a swarm response, which means half of the bees fly away with the old queen looking for a new house."

Cabin fever in the hive due to overcrowding is nothing new to honeybees, which is why Gross said it is too early for him to tell if global warming caused the last three Junes to be rainy and cold. But some of the first blossoms his bees go for during the spring are those of the black tupelo tree, which point upwards. Too much rain and all the nectar gets washed away.

The owners of Nantucket's two island vegetable farms, who rely somewhat on honeybees for pollination of their plants, also said it is too early for them to say whether global warming-induced climate change is affecting their crops.

John Bartlett of Bartlett's Ocean View Farm, who believes climate change is occurring, has yet to alter his growing schedule, functioning instead day to day and by when his customers are here buying his products.

A SANDBAR AT LOW TIDE

All the natural calamities that may or may not befall Nantucket are but details compared with the eventual inundation of the island by seawater. It is a fact: the island is going to be nothing more than a sandbar at low tide several centuries from now, but scientists believe global warming is accelerating our sinking.

"A lot of the changes we're seeing as far as temperature accelerations and acidification of the oceans, a lot of these changes are happening faster than predicted," said Chemical Oceanographer Dr. Sarah Oktay, director of the UMass Boston Nantucket Field Station. "Between 2050 and 2100, we'll see at least a meter rise in sea level."

However, in qualifying her estimate, Oktay explained that Nantucket is actually rising out of the Atlantic Ocean because of eustatic rebound.

Kind of like the foam of a cushion returning to its original shape after a couch potato gets up to get another beverage, eustatic rebound is the elevating of the earth's crust by magma pushing upwards after the retreat of the last glacier about 15,000 years ago.

Oktay added that the National Oceanographic & Atmospheric Administration (NOAA) estimates the ocean around Nantucket to be rising three millimeters per year. She could not say how much the island is still rising.

What could hasten sea level rise is melting sea ice at both poles combined with a warming of the oceans causing them to expand, said Oktay.

Where does this leave Nantucket? Eventually without much of Coatue, Eel, Great and Smith's points, part of Brant Point, Madaket around Hither Creek and the great salt ponds converted to tidal inlets open to the ocean.

WARMER AND DEEPER

Right now, the signs of rising seas are barely visible. They elicit more predications than revelations. Such guesswork can be found in the Siasconset Beach Preservation Fund's calculations for the amount of sand it expects to lose to sea level rise as part of its plan to renourish three miles of the island's eastern shore with 2.6 million cubic yards of shoal sand.

"The sea level rise accounts for 40,000 cubic yards of the 2.6 million yards for the project," said Rick Spadoni Senior Vice President of Coastal Planning and Engineering of Boca Raton, Fla. and SBPF's project manager. "If the future sea level accelerates, that number will grow."

Warmer ocean waters worldwide - an increase of two degrees Fahrenheit in the last century, or 30 times the amount of heat pumped into the atmosphere in the same time period, according to www.oceansalive.org - are producing some phenomenal sights. They include an abundance of tropical fish found in our waters last summer, some 40 species in all, such as the Northern puffer fish, Jack Cravalles, trunkfish, spot-fin butterfly fish, blue angel fish, short big-eye fish and hundreds of Portuguese man-of-war jellyfish, said Dr. Bob Kennedy, Director of Natural Science for the Maria Mitchell Association.

Hard-shelled sea creatures in Nantucket's harbors such as bay scallops, quahogs, moon snails and whelks may already, and certainly will, be suffering because the ocean is absorbing so much carbon dioxide, said Oktay.

This causes pH levels to rise, making the ocean more acidic. That in turn, eats away at these hard shells made of calcium carbonate causing shelled animals to expend more energy to protect themselves.

For bay scallops, one more degree of difficulty can be added when winter water temperatures hover around 45 degrees, preventing the scallops from going into dormancy, and causing them to work harder to stay alive as they lapse into and out of dormancy, said Town Biologist Keith Conant.

"Starvation is a potential possibility," he said. "There are other factors that haven't been evaluated yet because we haven't experienced the full effects

of global warming yet." I