I’ve been delaying writing about this topic because it’s
such a downer. But since it is an
important one, I’ll give it a go, so please bear with me... Our trees are dying. Someone who doesn’t know a lot about trees
(ie. most people) would consider this statement an alarmist scare tactic,
typical of the tree-hugging, over-exaggerating, environmental movement that constantly
spits out doomsday hyperboles in the futile hope of stirring the public towards
action. Unfortunately, to state that our
country’s trees are dying is no exaggeration.
Photo: Many street trees on Long Island have died because of the Asian Longhorned Beetle
Invasive insect pests and new fatal tree diseases are seriously
impacting our nation’s forests, our community’s street trees, and our own
backyards. Over the past century, global
trade has expanded exponentially and has inadvertently facilitated the
introduction of invasive pests into this country through various means
including wood packing materials. Insect
pests and diseases that are native to other areas of the world are able to cause
an alarming amount of damage to our trees.
Because our trees did not evolve with non-native or new insects or
diseases, they did not develop a natural defense mechanism to ward them off and
therefore succumb easily. What our trees
face today is analogous to what the American Indians faced when Europeans first
came to America. With no immunity
developed against Eurasian infectious diseases, Native Americans died by the
millions. Likewise, our native trees are
dying by the millions to diseases such as Chestnut Blight and Dutch Elm
Disease, the smallpox and bubonic plague of the tree world.
Photo: A mature American Elm exhibiting symptoms of Dutch Elm Disease; Garden City
It is incredible how quickly invasive insect pests and new
fatal tree diseases have altered and continue to alter the landscape. Among the most dramatic changes, our eastern
hardwood forests have lost an estimated 4 billion American Chestnut trees (Castanea dentata) due to the fatal Chestnut
Blight disease. Over 100 years after the
introduction of Chestnut Blight into the US via chestnut seeds or young plants
from Eastern Asia, the American Chestnut Foundation® is still trying to develop an
American Chestnut tree that is resistant to the disease. Meanwhile, oaks and hickories have grown in
where majestic Chestnut trees once stood.
But our oaks are at risk as well – in 1995 Sudden Oak Death
was first reported in California.
Serious efforts have been underway to make sure that this aggressive,
lethal disease does not spread to the East Coast where it could easily infect
our native oaks including Northern Red Oak (Quercus
rubra) and Pin Oak (Quercus palustris). But if you do see an oak tree around here
wilting and dying quickly, it’s probably the aggressive and lethal Oak Wilt
disease, first identified in 1944, instead of the aggressive and lethal Sudden
Oak Death.
I haven’t even mentioned some of our newer insect pests,
including the Asian Longhorned Beetle, first discovered in Brooklyn in 1996. The Asian Longhorned Beetle has killed tens of
thousands of trees in New York, New Jersey, Massachusetts, and Illinois, including
our beloved native Sugar Maple (Acer
saccharum). And then there’s the
Emerald Ash Borer, first discovered in Michigan in 2002, which is extripating
all our native Ash trees, including Green Ash (Fraxinus pennsylvanica) and White Ash (Fraxinus americana).
Photo: Despite extensive trapping and monitoring efforts like this purple sticky trap, the Emerald Ash Borer continues to spread and is expected to be found on Long Island in the near future
With these deadly insects and diseases, our entomologists,
plant pathologists, ecologists, and plant breeders certainly have a lifetime of
work cut out for them. Millions of
dollars in research, outreach, and education are being invested to contain or at
least slow the spread of certain tree pests.
But our trees are still dying and our natural world has already changed. It is disheartening to know that the woods I
occasionally hike through and the tree-lined streets I walk by are very
different from those that my grandparents and great-grandparents experienced.
In this day and age, it is difficult to have a positive
outlook on the future of our nation’s forests and trees. Perhaps there is some solace in knowing that
most people today who take a hike in our eastern woodlands don’t realize that
American Chestnut, American Elm, and Eastern Hemlock should be there, but are missing. Instead, they see a lush forest of uninterrupted
greenery. Ignorance may truly be bliss,
and I sometimes wish that I could go back and experience nature again without
knowing all the things that I know now.
But what about the future?
Do I dare wonder what our forests and landscapes will look like in
another 100 years? What trees will be
left? And more importantly, how many
people will remember all the trees we’ve lost?
Asking these questions makes me think of the concept of “shifting
baselines,” a term coined by biologist Daniel Pauly in 1995. Establishing a baseline or reference point
for a degraded ecosystem is important because then we know what we have to do
to work to restore it. But over time, undocumented
knowledge is lost, and the baseline can slowly and subtly shift until we accept
degraded habitats as “normal.” Perhaps
when the last Ash tree falls or the last Sugar Maple dies, our children will
never have known that baseball bats used to be made from the wood of ash trees,
or that maple syrup used to be made from Sugar Maple sap and not high fructose
corn syrup. Future generations may
accept forests devoid of these tree species as normal. It is therefore of utmost importance for
ecologists today to document as much information about our forests as possible,
so that we can relay this knowledge to future generations and prevent baseline
reference points from shifting too far.
Even if experts cannot stop the Emerald Ash Borer or Sudden Oak Death,
studying our trees and forests will not have been in vain. Sadly, scientists must come to terms with the
reality that our trees are in fact dying.
