The Unique Environment of Island Forests

Sea, salt, cool fog, and wind shape the wooded areas of islands

Story by Catherine Schmitt and photos by Jack Sullivan

Imagine being at sea for weeks, months, or years, seeing only blue, gray, and the foaming white of cresting waves. Imagine smelling only salt, minerals, fish, and then, one day, catching the faintest scent of something different, like honey mixed with cinnamon and turpentine. On the horizon, a black blur slowly resolves into solid green.

Trees, land, destination! Rock islands tufted with dark green spires, their needles sending aromatic messages into the wind. Forest. Earth. Home!

Maine island forests share many characteristics with the great North Woods that stretch across the northern tier of the continent. But, in many other ways, island forests are unique. Surrounded and shaped by the sea, island woods are influenced by cool temperatures, wind, waves, salt spray, and fog.

Especially northeast of Penobscot Bay, the coast experiences twice as many hours of fog because cold currents from the Arctic flow close to shore. Boreal evergreens like spruce and balsam fir flourish in the cool, moist climate. Salt-tolerant, fast-growing white spruce grow right along the seaward edge, their roots holding island soil in place. Red spruce, balsam fir, paper birch, yellow birch, and red maple are common.

These trees attract sharp-shinned hawks, yellow-bellied flycatchers and flickers, warblers, chickadees, and crossbills. Leach’s storm-petrels burrow in fallen logs and roots. Eagles nest on white pine branches high above the canopy.

Mammals are few on distant, isolated islands (meadow voles, masked shrews, maybe mink) but common on nearshore islands and include moose, deer, muskrat, porcupine, raccoon, red squirrel, snowshoe hare, and otters.

Mammals and birds feeding on mussels and urchins leave shells strewn about the woods, a small but not insignificant influx of marine nutrients.

The understory might include small firs, alder, sheep laurel, blueberry, and, right under the spruce, twin-petaled white flowers of dwarf enchantress-nightshade. But mostly, there are lichens—bloodstain lichens, granular lichens, budding tube lichens, crottle and beard lichens crusting ocean-facing trees—and moss. Big red-stem moss, stairstep and broom mosses, three-lobed and leafy liverworts cover the ground, and overtake fallen trees, of which there are many.

As Island Institute founder Philip Conkling wrote in Islands in Time, these forests are “the realm of the rugged.”

Islands bear the brunt of coastal storms, and windthrown trees define island forest form and function. As trees along the edge die and blow over, wind reaches more of the interior, blowing more trees down, creating gaps in the overstory where sunlight pours in and reaches plants on the forest floor. As a result of such intense and frequent disturbances, island forests tend to be younger, especially around their edges.

Maine island forests are also younger because so many of the islands were cleared in the last few hundred years.

In the Dawnland home of the Wabanaki, islands were and continue to be places for hunting, fishing, foraging, creating, living. But historically, indigenous people lost access as islands were among the first places colonized by Europeans.

In the warmer, drier region south of Penobscot Bay, colonists quickly cut large white pines along with hardwoods like oak, chestnut, walnut, and hickory. Later, they cleared spruce and fir on northern islands to make way for farming and sheep grazing, and trees were cut and sent to shipyards, lime kilns, and paper mills. They re-named islands after what they took from the forests: Hardwood, Clapboard, Stave.

Land clearing peaked in the second half of the 19th century. The varied histories of human use, along with differing geology, soil, climate, and exposure to wind and waves, along with the mystery of forces beyond human knowledge, mean that each island’s forest is unpredictably unique.

Take, for example, the small, domed island called Bar Island, at the head of Somes Sound on Mount Desert Island. Pines and oaks more than a hundred years-old shade an understory of scattered fir and birch. Standing dead trees are half-rotted, hole-ridden snags; others lay fallen across the ground and each other. Moss grows on stacked stones of an old well, and trees are choked by garden plants gone wild on the flat terrace of a one-time piazza. The mix of red and white pine and oak is unusual in the Acadia archipelago.