BSLA Fieldbook BSLA 2014 Fall Fieldbook | Page 38

BSLA / TOOLBOX m 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