More about this region:
Foster, David R.: "Hemlock", Yale University Press, April 29, 2014, 336pp, $30
A Forest Giant on the Edge
"Hemlock: A Forest Giant on the Edge" by David Foster (and seven co-authors) considers the recent (from the tree's perspective) history of the Eastern Hemlock: about ten to eleven thousand years. The primary focus is on the Harvard Forest, a collection of tracts surrounding Petersham, in north/central Massachusetts. From that base, Foster and his co-authors occasionally zoom out for a wider-angle view of New England.
Near-term, almost all Eastern Hemlocks appear to be doomed because of the hemlock woolly adelgid [uh-DEL-jid], an invasive Japanese insect. The adelgid's only natural enemy appears to be temperature below -13°F. This is why Hemlocks are dying south-to-north. Because of the overall warming trend — global and regional — whether any Eastern Hemlocks will survive is unknown.
Hemlocks' commercial value was real but limited: mostly, the tanin in its bark. The wood itself — not so much other than for pulp. No small thing though, Hemlock was and is valued for aesthetics. Because of the Eastern Hemlock's efficiency in absorbing sunlight and water, Hemlock forests are unique ecosystems and are notably cooler and drier than trees and forests that replace them. Of course, a hemlock forest floor is alive, but it's alive with species that do well with no direct sunlight and not much water.
Repeatedly, I find one of the most rewarding aspects of the book is the time frame — centuries and millennia — that's required for the "action" — what's going on. That time frame is a respite from the pace of current news away from the forest. The 1938 Great New England Hurricane weaves its way through the book because of the extent (geography and intensity) of the destruction in the storm's path, broadly devastating forests as well as the built environment. Also mentioned (e.g.: pg 176) are other hurricanes (1815, 1788, 1655) that left long-lasting evidence. I tend to think of geologic records as being, you know, geological. The historic record "Hemlocks" explores includes the trees — living, dying, and dead — and seamlessly extends to the underlying soil and terrain.
A minor quibble that doesn't rise to a complaint: there could be more and better maps. One historic source of relevant records (pg 61) was "...detailed map(s) of North American Forests before they were first cut and then cleared. For this, we can thank a largely anonymous group of seventeenth- and eighteenth-century land surveyors [that] recorded the presence of individual trees by their species and sometimes by their size [and] identified and blazed 'witness trees' as permanent markers at the corners of individual lots ...." I'd enjoy seeing some of these maps.
This isn't a book for or about tree-huggers. The authors repeatedly focus on the changing ways, over time, that humans have lived with and interacted with trees and forests. It's also an appreciation of Eastern Hemlocks, not a lament about their demise. Looking ahead, loss of Eastern Hemlock will likely lead to substantially greater biodiversity, greater water flow in regional streams with more species and more abundance and, overall, greater productivity. We will also lose Hemlock, a "...flagship for old-growth and primeval forest in the Northeast. We'll lose distinctive variation..." but "... the fastest route to recovery is simply to let the impacts play out and allow nature to recover as it has for millennia before." If history is a guide, this will take at least 500 to 1,000 years. Or longer.