Twilight of the Sugar Maples

Article Tools

Print

E-mail

Comments

RSS

This may seem an odd thing to envy in their lives, I suppose, but increasingly I do. I worry about threats to the trees, most of them human in origin yet beyond my control: insects like pear thrips, gypsy moths, and Asian longhorned beetles introduced from other parts of the world via global networks of commerce; acid rain; increased solar radiation resulting from ozone depletion; and global climate change. The last is particularly troubling. Computer models developed by scientists from the USDA Forest Service predict that virtually all of the contiguous United States, including Wisconsin, will be unsuitable for sugar maples once atmospheric carbon dioxide reaches double its preindustrial levels, something the Intergovernmental Panel on Climate Change estimates will happen within 100 years.

The average time of the sap run has, in fact, already changed. When John Burroughs was sugaring in his part of New York, the climate was noticeably cooler than it is now. Born in 1837 just four months before the Ojibwe formally lost what became my family's farm, Burroughs learned to expect that in the Catskills the sap would run near the vernal equinox, as it does now in northern Wisconsin. Our sugar bush is 200 miles farther north than the Catskills, however, and the sap run here would likely have fallen after the equinox in Burroughs' day. Not many Euro-Americans were in northern Wisconsin then to note it, but the Ojibwe were. Brethren of the Algonquin tribes who are believed to have first taught colonists from France and England to tap maples, the Ojibwe have visited seasonal sugaring camps for centuries. Tellingly, the early Ojibwe lexicons from what is now Wisconsin and Minnesota translate Iskigamizigegiizis, or Maple-Sap-Boiling Moon, not as March but as April.

The problem for maples in global warming, of course, is that the climate will deviate relatively quickly from precedents in the trees' genetic memories. Sugar maples can cope with the temperature extremes in the interior of our continent because the climate, although dramatic in its swings, is rhythmically variable at the scale of the seasons. The local, periodic fluctuations of light and temperature and precipitation caused by Earth's wobbling orbit are the obstacles -- and opportunities -- through which the tendrils of the trees' DNA have wended from one generation to the next, and the trees' DNA reflects this in both its sequencing of base pairs and, more figuratively, its helical form.

One early cliché of Western anthropology was that moderns consider time an arrow, whereas primitives consider it a circle. More apt than either as a concept for life's earthbound experience of time is the helix. In the geometry of relativity, an orbiting planet mapped in space and time cuts just such a figure, the planet corkscrewing through space-time as each revolution brings it to a position analogous, but not identical, to the one it held the year before; the well of gravity around the sun loops time back toward itself, but time's momentum keeps the circle from closing. Thus, when the winged seeds of the maple -- called "keys" or "samaras" by botanists and "helicopters" by children -- spiral down freighted with the next generation of trees, they mime the deep structure of both the hidden life they bear and the long history that shaped them. That the silhouette of a DNA molecule is a microcosm of Earth's movement through space and time is another masterpiece of chance. In an odd twist on Genesis, space-time has created life in its own image.

RSS | Comments | E-mail | Print