American chestnut had none. The American chestnut was king
of the forest – its nutritious nuts used by people and wildlife,
its straight-grained, decay-resistant wood in demand for everything from framing timbers to furniture, shingles to piers.
But by the 1940s, virtually all the American chestnut trees in
the eastern forests – some four billion of them – were dead, the
species reduced to scattered survivors and stump sprouts that
are doomed to die again and again. Most people alive today have
never seen a mature American chestnut.
The chestnut blight is emblematic of what happens when
a non-native disease or pest gets loose in a new environment,
where no resistance or immunity has been built up, and there
are no natural enemies to keep its population in check. It’s the
forest’s equivalent of what happened to Native Americans when
Europeans brought measles, influenza, and smallpox to the
shores of the New World: a tragedy.
Similar tales abound. Around the same time that chestnut
blight made its way to North America, another devastating
disease, white pine blister rust, was imported on European pine
seedlings, requiring a massive government response. In 1930,
Dutch elm disease was imported with a shipment of unpeeled
veneer logs from Europe, and it wiped out America’s favorite
street tree by the millions. Trees in their natural habitat, on rich
soils in valley bottoms, have also disappeared. Then there’s beech
bark disease, first noticed in the U.S. in Massachusetts in 1929.
Butternut canker appeared in the middle of the twentieth century.
Hemlock woolly adelgid, an aphid-like sucking insect, came from
Japan to the East Coast in the mid-twentieth century and has devastated eastern hemlocks. The balsam woolly adelgid turned the
Fraser firs on the slopes of the southern Appalachian Mountains
into ash-colored sticks. And as the twentieth century turned into
the twenty-first, a small, shiny green beetle from China was found
in Detroit, Michigan, munching on ash trees. Called the emerald
ash borer, it proceeded to kill millions of ash trees in two dozen
U.S. states and two Canadian provinces and is still spreading.
The problem of imported tree-killing insects and diseases has
been around for a long time. Unfortunately, despite the fact that
we know how these tragedies generally play out, some experts
say we haven’t taken all of the steps needed to curb the importations. The fight to prevent exotic forest pests from entering the
U.S. – and from expanding their beachhead if they make it in
– is underfunded and plagued by foot-dragging bureaucrats
who don’t want to rile a pro-trade lobby that views anything that
slows imports as bad. Perhaps worst of all, it lacks a constituency, an organized and vocal group of concerned citizens who
are willing to press policymakers, including Congress, to take
things seriously and move expeditiously to improve the nation’s
defenses against forest and agricultural pests and diseases.
“This is the most severe and urgent threat to forest health . . .
certainly in the eastern U.S., though I think you could make the
argument for throughout the U.S. And it’s underappreciated,”
said Gary Lovett, forest ecologist and senior scientist at the Cary
Institute for Ecosystem Studies in New York.
There are other threats to the forest, of course, including
native insects and pathogens, but “imported forest pests are
the only type of forest disturbance that can wipe out whole
species and sometimes whole genera in a matter of decades,” said
Lovett. And, he noted, it’s costing homeowners millions in taxes
to cut down trees and millions more in lost property value.
“It’s an awful situation right now, and it’s only going to get
worse,” said Scott Schlarbaum, a professor of forest genetics at the University of Tennessee and the author, with Faith
Thompson Campbell, of three landmark “Fading Forests”
reports that look at the problem of exotic forest pests. Their
latest report, Fading Forests III: America’s Forests – What Choice
Will We Make?, came out in 2014.
Let’s put some numbers on “awful:” According to Fading
Forests III, at least 30 new tree-killing insects and pathogens
have been detected in the U.S. since the turn of the twenty-first
century. That brings to 475 the number of known non-native
forest pests and diseases in the country. New arrivals include
polyphagous shot hole borer, which sounds ominously like
something spawned at the foot of Mt. Doom; laurel wilt; the
thousand cankers disease of black walnuts; and gold-spotted oak
borer. Of the 475 here now, at least 62 are insects. Seventeen are
pathogens that have been deemed “high impact,” with serious
economic and ecological effects.
“Now there is an exotic pest threat to nearly every dominant
tree species in the eastern deciduous broadleaf forest – a major
landscape component in 20 states,” reported Fading Forests III.
When it comes down to it, these pest and disease importations
are all the result of trade.
No one brings in exotic tree-killing pests purposely. The pests
stow away on goods bound for the U.S. Sometimes, as was the
case with chestnut blight and white pine blister rust, they arrive
on tree seedlings. Horticultural imports bound for the backyards