Where I live, the vast majority of Helene’s destruction was caused by 100,000 acre-feet of water dumped on our valley over the course of 44 hours. We had our share of trees downed, but our valley was spared the worst of the cyclonic winds. As my work takes me further afield, I’ve witnessed places where the wind did more damage than the water alone. For weeks, I’d been hearing about astonishing wind damage in parts of Yancey and extensive swaths of Mitchell County, but until I travelled the Blue Ridge Parkway from Asheville to Mt. Mitchell, I had not witnessed it firsthand.
Every winter our home and woods are buffeted by serious winds, often gusting over 50 mph. Wind season typically runs from November to April, with the strongest winds arriving with powerful cold fronts from the northwest. The elevation of our valley floor is 2600-3000’; in the high mountains surrounding us (including the tallest peaks in eastern North America, elevation 6,000’+), winter winds can be especially fierce, occasionally gusting over 100 mph.
Helene’s winds were uniquely destructive for three reasons: they were preceded by an enormous amount of rain, they came from an atypical direction, and, most crucially, they arrived during the growing season; Helene blew into the mountains while the low-elevation hardwood forests still had most of their foliage. Water, along with CO2, is a key ingredient in the recipe of photosynthesis, and during the summer trees are enormous pumps, transporting vast amounts of water from their roots in the soil to their leaves in the canopy. Water is heavy, so during the summer trees are top-heavy, literally water-logged from their trunk to their leaf tips. The wetter the soil, the heavier the treetops become. The very nature of a leaf is to provide surface area to absorb sunlight, and this surface area can turn a tree into a sail. This combination of topheaviness and surface area makes broadleaf trees (which make up the majority of our low-elevation forests) very vulnerable to summer winds. Every fall broadleaf trees drop their leaves and much of the water drains from their canopy. During the winter, trees are light and trim up top, prepared to withstand the force of powerful winter winds and the weight of snow and ice storms.
Some of Helene’s water had been drawn into the treetops by the time the winds arrived early Friday morning, but even more of it saturated the soil. The trees were pummeled by winds, only a bit stronger than winter winds, but their tops were heavy and sail-like, and their roots were anchored in soft, wet soil. It’s a testament to the strength and ingenuity of trees that there are any left standing at all.
On the drive from Asheville, the Parkway curves along the contours of the southeast facing slopes of the Blue Ridge escarpment. The wind damage shifts from moderate to extreme as you get close to 3000’ in elevation. Nearly every southeast-facing slope between 3000’ and 4500’ has suffered catastrophic wind damage, often exceeding 50% of the forest. In places, 80%-90% of the forest canopy is down or damaged. Sheltered coves and southwest-facing slopes are far more intact. Once you get close to 5,000’ as the Parkway approaches Craggy Gardens, the forest changes and the wind damage completely dissipates. Winds have cultivated these high-elevation forests for millenia. The hardwoods at 5000’, beeches, birches, and oaks, are stout – the canopy is half the height of lower elevation “cove forests.” Along the most exposed ridges, the trees attain a krummholz aspect. As you get higher, the hardwoods fade altogether, and the conifers – spruce and fir – take over. These flexible trees don’t even drop their needles in winter, and they are very accustomed to wind.
This week the National Weather Service released their official report on Helene’s winds. They made this map, extrapolated from a combination of local wind readings (106 mph on Mt Mitchell!) and satellite and LIDAR imagery of the change in forest canopy. You can see the heaviest winds are in the corridor along the Blue Ridge, to the high elevations of the Craggies and the Blacks. The wind map looks a lot like the precipitation map, with the most extreme conditions shifted north and slightly east. The uplands of Buncombe, McDowell, Yancey, Mitchell, and Avery counties fall in the overlapping portions of an oddly-shaped and ominous venn diagram. Contrary to anecdotal reports and homespun analysis of wind damage, the NWS and the NC State climate office firmly state that none of the wind damage in the mountains from Tropical Storm Helene was the result of tornadoes.*
I’ve heard and read a lot of hand-wringing about the destruction of NC’s great forests. I’m not mourning this particular aspect of the event. It is certainly a great ecological disruption, but it’s a natural one. I love seeing enormous rootballs in the woods. I think of wind-toppled trees as a slow and sustainable tilling of the forest’s soil, bringing rocks and minerals to the surface, creating habitat for critters and food for fungi.
By their nature, forests are incredibly resilient systems; the vast majority of WNC’s forest is intact, and the disturbed acres will go through a process of succession. The ecologist in me is curious to see what that will look like. What tree species will thrive in the canopy openings? Might this episode be a turning point for grouse, bobwhite, or golden-winged warblers, all species that depend on openings and new growth in the forest? The mushroom hunter in me imagines great bounties of oysters and chicken of the woods in coming years. I’ve spent time in New England forests that were disrupted by the Great Hurricane of 1938, and some say that they are better off now on account of that storm’s winds.
I mourn for those who lost loved ones or homes; I don’t mourn Helene’s effects on our forests. There is plenty to mourn in regards to our forests: I mourn the extinction of the passenger pigeon and the American chestnut; I mourn the extirpation of bison, red wolves and mountain lions, ash and hemlock trees. I’m grappling with the fact that many holes in the canopy will be reoccupied by Asian bittersweet and Chinese privet. Gashes on streambanks will regrow with Japanese knotweed and stiltgrass. This is the new world order, but it’s not Helene’s fault.
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