But what of my own mountain, the one I’m a tenant on? I’m afraid I know it too well to idealize it as Li Bo or Du Fu might have done. Besides, its very status as a mountain can be debated – though the long, low ridgelines of the folded Appalachians and Ouachitas are globally unique and nothing to sniff at. My exact topographical circumstances here can be tricky to put into words. My house sits near the head of a transverse hollow (Plummer’s Hollow) in the end of a ridge (Brush Mountain) that the hollow divides in two. Thus with equal justice I could consider myself the inhabitant of a mountaintop or of a high valley.
What’s certain is that, biologically speaking, this mountain has seen better days. In the first half of the 19th century, all the steep hollows and ridge sides in what used to be called the Upper Juniata Valley were ravaged repeatedly by charcoal makers. For those few short decades, Juniata Iron underwrote the Industrial Revolution. Plummer’s Hollow must’ve been clearcut for the first time around 1815; the river-powered Upper Tyrone Forge was founded at its mouth in 1813. It probably would’ve been clearcut again a mere 30 years later. Merely by counting the charcoal hearths that still remain in our 3rd- and 4th-growth forest, I can get a glimpse of the tremendous size and number of trees that must once have stood here.
The loss of soil due to erosion would’ve been tremendous – by some estimates, possibly as much as 15 inches’ worth. The work of millennia, gone in a few short years. The character of the forest has changed dramatically since the early 19th century, not only in the obvious species composition of canopy-height trees, but in the loss of entire biological communities whose richness and complexity we can only guess at. To pick one example, the northern flying squirrel-old growth hemlock-micorrhizal fungus-bacteria association depends on the presence of all four components (and possibly more we don’t know about); when one is gone, the rest will follow. Species dependent on moist, cool, forest interior habitat or with other more specialized requirements are long gone. In fact, I just learned a few days ago that the westernmost ridges in this part of Pennsylvania are unique for the virtual absence of a lungless salamander species, the red-backed salamander, which has been found in such abundance on identical-looking ridges to our east as to equal in biomass all other vertebrate species combined. Why don’t we have it? Was it once present, wiped out by the frequency and intensity of clearcutting in the 19th century? We’ll probably never know.
Repeated clearcutting is far from the only ecological wound this mountain has suffered. At least one fire, probably triggered by a charcoal fire that got out of control, burned well over a hundred acres, destroying seeds and seedlings that might otherwise have regenerated. The loss of the passenger pigeon and the American chestnut had huge consequences for forest composition throughout the East. The extirpation of the two top carnivores, gray wolf and cougar, had complex ripple effects, including what ecologists call mesopredator release – the unnatural abundance of mid-sized predators such as raccoons, skunks and bobcats, with severe repercussions for their own prey species.
The loss of top carnivores in combination with the unnatural proliferation of young forests and edge habitats has led to catastrophic overbrowsing by white-tailed deer for most of the last 80 years. Forest succession has been radically altered and in some cases curtailed altogether. These and other impacts work in concert. For example, severe air pollution – chiefly ground-level ozone and acid precipitation – is changing soil chemistry, in turn favoring a few deer-resistant, invasive species such as New York and hayscented ferns and the non-native Japanese barberry and stiltgrass. These latter species have been found to further alter soil chemistry and composition on their own. This process is greatly abetted by the actions of non-native earthworms, introduced deliberately or accidentally to forest soils in this region over the past 200 years. For at least the past 20,000 years, forests as far as 200 miles south of the glacial line have been free of earthworms. The forest communities native to Central Pennsylvania were thus dependent on a chemical balance and depth of leaf litter that may never return.
One final impact, out of many more I could describe, remains largely unknown: the cumulative effects of global climate change. We are already seeing an increased frequency of natural disturbance events that makes us agonize more than ever about the extent to which anything we now observe can be called natural. Icestorms, hurricanes, wildfires and native insect outbreaks are all part of natural disturbance regimes. They are elements of native biological diversity as critical as the presence of native communities, species and genomes. But the other impacts I’ve listed are already straining the natural resilience of the ecosystem. Add global warming to the mix, and the radical simplification or complete collapse of entire ecosystems looms on the horizon. Much of Penn’s Woods may turn to savanna within my lifetime. Already on the mountain one can find open patches as large as several acres each that haven’t supported a closed-canopy woods in decades. This phenomenon can be observed throughout the state.
As Aldo Leopold famously noted, “One of the penalties of an ecological education is that one lives alone in a world of wounds . . . An ecologist must either harden his shell and make believe that the consequences of science are none of his business, or he must be the doctor who sees the marks of death in a community that believes itself well and does not want to be told otherwise.”
If it were only the allegedly uninformed masses who persist in whistling in the dark, our task as conservationists wouldn’t seem so daunting. But over the years I’ve encountered all too many foresters and wildlife professionals who refuse to recognize the numerous elisions in their own view of what is natural and what isn’t. Especially in the last couple of years, as I’ve become a vocal advocate on behalf of the fledgling Pennsylvania Wildlands Recovery Project, I have encountered widespread, sometimes willful ignorance of the problem of shifting baselines for ecological recovery. That is to say, the vast majority of professional conservationists speak in terms of sustainability, which seems to imply simply accepting the status quo as a baseline for evaluating the future health of the ecosystem.
I don’t know which human characteristic has had more disastrous effects over the millennia – our natural acquisitiveness, our limited imaginations, or our short and highly selective memories. Over a thousand years before Li Bo and Du Fu sought mystical oneness with the mountains, a Chinese philosopher named Mengzi (a.k.a. Mencius) penned the following parable. This captures the whole problem of shifting ecological baselines as well as anything I’ve ever read:
Ox Mountain once was covered by trees. But it had the misfortune of standing too close to a city. People came with their axes and their hatchets; they climbed all over the mountain. They cut down the trees, stripped the mountain of all vegetation.
Nevertheless, the night breeze wafted over its slopes. Rain and dew fell; everywhere sprouts of green began to show. But cattle and sheep had been let loose to pasture on the mountain. Before too many years had passed, it stood gaunt and bare. Today, people see its barrenness and can’t believe the mountain wasn’t always that way.
Who can tell when forests have been altered, cut down with axes, demolished with hatchets? Day after day the trees are cut down. How will the mountain ever recover?
It’s just as Confucius said: “Preserve it and it will remain. Let it go and it’s gone forever. One can never be sure what one has, and when it’s enough. Afterwards one can never tell just where it went.”
It seems these words of the master were aimed straight at the heart.