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and impact. When we design for a zone
we must consider that whatever we plant
in the ground will be chased by a shifting
climate. Despite the fact that the UPHZ will
be updated, it is not a projective tool, rather
it is an increasingly precise measure of
current conditions.
Even without major human influences,
we know that climatic change leads to
catastrophic loss for dominant forest
species. Tsuga canadensis, the Canadian
hemlock, went into near catastrophic
decline about 5,700 years ago. While
the hemlock looper (Lambdina fiscellaria)
seemed the immediate culprit, recent
studies point to a climatic change that set
up xeric conditions, which ultimately made
the species more vulnerable, triggered
dieback, and expanded attacks of predatory
insects and pathogens. In a brief 500-year
period, the Canadian hemlock, sprouting
from its ecological reserves, regained
dominance as a wetter climate returned.
NEAR RIGHT
Sequoiadendron
giganteum
Blithewold,
Bristol RI
36
BSLA
Echoing this decline is the current and
rapid loss of this same species brought
on by the woolly adelgid (Adelges tsugae),
which should also be viewed as a climatic
effect rather than a plague of pestilence.
It is one example of many eastern native
plants such as chestnut, ash, birch,
certain elms, etc. that are no longer part
of a landscape architect’s toolbox due
an apparent rezoning of the forest. The
question remains as to what will repopulate
the void and from what reserve.
Reintroductions
As landscape architects we consider time,
culture and their effects differently than
most professions. Fellow zone pusher John
DeWolf, planted the now 100-year-old giant
sequoia at Blithewold Mansion in Bristol,
RI. The existence of this tree proves that the
potential has existed to grow a Sequoiadendron
giganteum on the east coast for at least the
past one hundred years. The symbolic ironies
of this particular sequoia tree include that
its lifespan marks the time frame that our
industrial activities began to have global
climatic repercussions, the other is that coal
barons built the Blithewold estate.
Although novel, and some may say nonnative, in our current framing of time, this
occurrence of the Sequoiadendron is not the
first in the eastern forest; in fact, that occurred
200 million years ago in the Triassic period.
Sequoiadendron then became the dominant
forest of North America, Greenland and
Eurasia in the Jurassic period. Chased by
glaciers and isolated by the movement of the
Earth’s crust, they are far from dominance now
and live in what is considered a fragmented
community or, more optimistically, an
ecological reserve. Currently residing on the
West Coast, it is one of the oldest surviving
native trees of the Eastern Forest.
Is it now time to tap the reserve and promote
the re-establishment of the sequoia forest
of the east, in order to sequester carbon and
acclimate to our changing planet. This is a
scalar response based on the fact that with our