Eastern old growth hemlocks

Old Growth Eastern hemlocks on the Hemlocks and Hardwoods Trail of Kejimkujik National Park. Credit: Zack Metcalfe

A Change in the Overstory

Nova Scotia’s Scramble to Save the Eastern Hemlock

Stepping into old growth has always felt like coming up for air. The vast majority of Maritime forests are young, defined by stifling, low-hanging branches and congested regrowth. White spruce and Red maple grapple and intertwine in pursuit of the sunlight, the air often hot, dry and buggy, their woods impassable except by trail. But discover a scrap of Maritime old growth, relatively intact for centuries or more, and it will play on your primitive primate brain in ways both pleasing and profound. Suddenly you can stand up straight, you can see for relevant distances, the air will be cool and gently humid, and the trees, of course, will be mighty, spaced wide enough apart for the easy passage of moose or deer or human beings, their trunks straight and stately like the pillars of a cathedral, holding aloft a canopy democratic in its use of sunlight, the sort of woody infrastructure it takes lifetimes to negotiate.

These forests are difficult to find. It is estimated that, prior to Columbus, as much as half of the forest landscape was old growth at any given time. Today, that number’s closer to 1 per cent, most of which is probably tucked away in Nova Scotia. In a good year, I might have occasion to visit two or three stands, the surviving scraps of what is sometimes called the Acadian of Wabanaki forest type, a blend of boreal and temperate tree species unique to the Canadian Maritimes.

This year I have seen only one, in Kejimkujik National Park, Nova Scotia, down the aptly named Hemlocks and Hardwoods Trail. Walk it long enough and you will stumble from the tangled tightness of relatively young woods into a grove of exceptional openness, built of trees in excess of 400 years old, some perhaps exceeding 500. Almost without exception, they will be hemlocks.

This is a quirk of Nova Scotian old growth. Of all the native species best suited to ancient forests – White pine, Red spruce, Yellow birch, Sugar maple, White ash, American beech – Eastern hemlock has been the luckiest. Its saving grace has been its worthlessness. While White pine was harvested feverishly to build ships during the Napoleonic Wars, and Yellow birch was felled in the name of veneered furniture, Eastern hemlock remained of limited economic value. Time and again the mature and maturing Wabanaki Forests of Nova Scotia were picked over for quality lumber, and the oldest trees they left standing were invariably Eastern hemlocks. As a consequence, this single species composes a significant sum of our surviving old growth forests, anchoring regional biodiversity largely by itself.

The Hemlocks and Hardwoods Trail is a case in point. Loggers were in this grove perhaps a century ago, but its titanic hemlocks were left unmolested, overlooked in favour of neighbouring Red spruce and White pine, these alternative treasures cut down and hauled out. Wildfires have scorched much of southwestern Nova Scotia in the century since, Kejimkujik in particular, but these hemlocks were spared once more, their waterlogged tissues perhaps frustrating the flame. But when I visited this trail in late June, I did so knowing the luck of these hemlocks had finally run out.

Hemlock Woolly Adelgid (HWA) is an aphid-like insect native to East Asia as well as the western coast of North America, living in ecological equilibrium with the hemlocks of each region. It feasts on these hemlocks and is, in turn, feasted upon by a suite of predatory and parasitic insects, never rising to population densities of any particular concern. But sometime in the early 1900s, HWA was accidentally introduced to Virginia, its presence formally documented in the City of Richmond in 1951. Since then it has spread north and east, until its discovery in southwestern Nova Scotia in 2017, and in Kejimkujik National Park the following year.

Hemlock Woolly Adelgid
The egg sacs of Hemlock Woolly Adelgid affixed to the underside of hemlock needles. Credit: Zack Metcalfe

HWA has encountered no natural predators in eastern North America, reproducing with impunity at the expense of the Eastern hemlock, its primary victim on this new frontier. To date they have killed over a billion trees, affixing themselves to the underside of hemlock needles and patiently sucking them dry. Entire landscapes in New England have faded to grey with the death of their hemlocks, and several forests in Nova Scotia have already begun to wither. In Kejimkujik, the effect will likely become visible within the next couple of years, but we, the onlookers, are not entirely powerless.

HWA is a pest, and pests require pesticides, an uncomfortable reality for any member of the conservation community. The only way, it seems, to preserve the oldest and most significant of Nova Scotia’s Eastern hemlocks is to inoculate them periodically against HWA, employing chemicals with names like IMA-Jet, TreeAzin and Xytect 2F, unlikely heroes in our counteroffensive against an invasive insect. But if I’ve learned anything from my time covering this crisis, it is that the non-target effects of these pesticides will be far outweighed by the ecological shock following the mass death of hemlocks, their evergreen forests often replaced by bushy glades of fern or rhododendron, considered by some to be deserts of biodiversity. And no matter how zealously these chemicals are applied, the underwhelming majority of trees will never be treated. There are simply too many of them, occupying too much of the landscape, and treatments cost money. Only our finest trees will be inoculated, and only our most concerned citizens and institutions will care enough to do the inoculating. Thankfully, Parks Canada ranks among them.

Kejimkujik National Park, which stewards some of the most significant Eastern hemlock old growth in the Maritimes, has played a central role in our fight against HWA, spending $2.1 million identifying its most valuable stands and beginning their inoculation. The Hemlocks and Hardwoods Trail had 429 trees treated with IMA-Jet this past fall, with an additional 117 treated experimentally with Xytect 2F. Other treatments persist in key campsites, and between now and the end of 2023, over a thousand more will be treated throughout the park, in sites along the Mersey River and deep in Kejimkujik’s interior, beyond the reach of roads, where forests still more ancient await this unorthodox rescue.

There may be a solution to HWA, one presently being assembled by the Canadian Forest Service and its partners in the United States – recruit the parasitic and predatory insects controlling HWA populations in western North America and introduce them here, so as to strike some ecological balance. But proving the safety and effectiveness of this approach will take time, and implementing it at scale will take more time still, so we must wait, and preserve as many trees as we can, like those titans along the boardwalk of the Hemlocks and Hardwoods Trail, whom we’ve granted a 5-7 year reprieve at the end of a needle. I didn’t seek out these ancient hemlocks because I’ve lost hope. It’s just that, in our struggle to save the mightiest of our Eastern hemlocks, there are no guarantees whatsoever.

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Eastern Perspectives

Zack Metcalfe is a freelance journalist, columnist and author based in the Maritimes.