Hurricane Lizards and Plastic Squid by Thor Hanson

Author:Thor Hanson [Hanson, Thor]
Language: eng
Format: epub
Publisher: Basic Books
Published: 2021-09-28T00:00:00+00:00

FIGURE 10.1. Talus slopes in New England capture cold air amongst their cobbles, creating conditions for conifers and other boreal forest species to persist within a landscape dominated by hardwoods. Illustration © Libby Davidson.

“It’s basically refrigerated air,” Daniel told me recently. I called her at home in Vermont—two decades after our first meeting—to hear her explain again how cold, dense air can sink through a talus slope and trickle out at the base, creating its own tiny climate. While the surface of the rocks may heat up on a sunny day, that energy never penetrates to the shady depths below, and nighttime always brings a fresh chill as the rocks and surrounding landscape cool. At Bristol Cliffs, the effect is enhanced by ice that fills the deepest cracks during winter and remains frozen for much of the year, and by a shelf of bedrock beneath the talus that funnels the downdraft to a site suitable for trees and shrubs. The result is a habitat in miniature, a patch of cold ground Daniel estimates as “about the size of a swimming pool.” Beyond that zone the chill dissipates, but within it grows a flora that is distinctly out of place. And, just as remarkably, out of time.

Turn back the clock far enough in Vermont, or anywhere else in New England, and you wouldn’t need a talus slope to find refrigerated air. Eighteen thousand years ago, the entire region lay under a continental ice sheet that stretched from the Arctic south to the vicinity of modern-day New York City. After the ice retreated, tundra plants established first, followed by a boreal forest that blanketed the landscape for over 2,500 years. As the climate continued to warm, however, those conifers shifted steadily northward to be replaced by hardwoods. That is to say, most of them shifted. Wherever things remained cold enough—be it a mountainside or a peculiar patch of talus—they did something else. They took refuge. It is entirely possible, even likely, that the handful of spruce, fir, and other boreal species at the base of Bristol Cliffs have persisted there for thousands of years, generation after generation, making the most of that trickle of chilly air while the forest all around them warmed up and changed. The alternative explanation requires an implausible series of long-distance dispersal events, with the seed or spores of every northern species in the grove traveling scores of hundreds of miles and just happening to land on that one suitable fraction of an acre. Either way, the lesson is one of cause and effect: plants and animals respond to the conditions their landscape provides, no matter how atypical or idiosyncratic. In the context of adjusting to climate change, places like Bristol Cliffs provide their few lucky residents with an appealing option: business as usual.

“Whatever was growing there was always atypical,” Daniel mused, when our conversation turned to the postglacial history of the talus slope. Tundra species probably persisted at Bristol Cliffs long after conifers moved into the neighborhood, just as the conifers are now embedded in hardwoods.

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