An exotic insect, the hemlock wooly adelgid, is causing widespread mortality of eastern hemlocks across the eastern United States, where this important conifer grows in dense groves in the Northeast but occurs in sparser stands in the South.

After the infestation attacks a hemlock, a white coating develops on boughs before desiccation soon limits new growth and causes fallen needles, which can result in death in four to 10 years. Even if a hemlock survives, secondary causes may kill the weakened tree.

Losing mature hemlocks hurts songbirds like Blackburnian warblers and golden-crowned kinglets and game like ruffed grouse and white-tailed deer — to name four.

Blackburnians nest in hemlocks, and golden-crowns, grouse and deer use this tree for shelter from intense cold, wind and deepening snow in late fall. In fact, deer cannot survive severe winters without hemlock (or cedar) canopies on mature trees. The interlocked boughs protect them like a roof.

Hemlock also shade brooks and streams in summer, keeping water cool for brook trout, cold-water baitfish and other heat sensitive critters.

On top of the infestation crisis, woodcutters remove hemlock for lumber and other uses, and in fact, harvesting North Country hemlocks (and cedar) has severely distressed the whitetail herd there, which now averages two deer per square mile, making people wonder if deer hunting should be closed in northern and eastern Maine until the herd rebuilds itself.

When I was 4 years old, across from my boyhood home, woodcutters built a tote road straight down a ridge for 3/4-miles from the main highway. There, in the middle of the forest, sawyers and woodcutters set up a portable sawmill and cut lumber for two years. Early childhood memories include loaded lumber trucks with groaning engines, coming from the woods.

When I was 6 years old, the workers closed the temporary mill and removed equipment. A year later, my love affair with hemlocks began. My relatives and friends started walking down the well-defined tote road to the abandoned site, marked by huge piles of sawdust, slabs and edgings.

That year, my grandmother told me that a spreading hemlock grove grew on the ridge’s east slope, overlooking a mile-long meadow. My grandfather, Harold French, hunted there and trapped along a brook running along the edge of the hemlocks. The grove impressed him enough to traipse into the woods with my grandmother to show her the spot.

Naturally, after my grandmother gave me the family history of the hemlocks, the dark setting under the dense canopy captured my imagination. After 50-plus years of hunting, hiking and birding there, this hemlock stand offers me a near-religious experience whenever I visit this spot.

Nature gives, takes and then gives, though. People may abhor habitat destruction that stresses wildlife, but in truth, adelgid infestations killing trees create homes for species such as woodpeckers and other cavity-nesting species as well as herbaceous forage for critters that eat greens springing up in the newly sunlit spaces. The list goes on.

Losing most of a tree species over a vast region is nothing new. Long before my birth, most butternuts with their important mast crop died off. During my lifetime, we have also witnessed American elms pretty much disappear and are now watching the demise of American beech.

In some Maine townships, it’s difficult to find a single beech tree without those telltale pockmarks on the bark, evidence of beech-blight disease. Dead beeches are a common sight.

When an entire tree species dies off except for a few specimens, it depresses those of us who notice such things, but in nature’s scheme, hemlock and beech woes constitute yet another stage in forest successions.

Also, humans often love nature loses that allows them to make money. For example, white-pine lumbering in Maine in the 19th century eliminated huge pine forests, but beech filled the void. Beechnuts feed game animals such as deer, bear, moose and grouse, great for tourism aimed at hunting and wildlife watching.

Humans want nature and development to remain exactly the same as it was in their youth or during the first time they move to an area. For instance, I first lived in Belgrade Lakes village in January 1980, and that initial introduction became my standard of perfection for a village. For me, though, this hamlet now has a different feel.

The only constant we’ll ever know over the span of a long life is change. We witness so much transformation, but for me, some hemlock groves have created the one exception because of their longevity in comparison to other New England trees. Hemlocks can grow four centuries, and a handful of them last 600 years.

In short, many old hemlocks germinated when pilgrims arrived at Plymouth, and some Maine hemlocks go back to when Donatello created the statue of David. That’s longevity all right through myriad generations.