Thursday, April 18, 2013

Chet Raymo, “Navigating”

by Chet Raymo

“My ignorance grows by leaps and bounds. I try to keep up. I read "Science" and "Nature" every week. I check the new-book shelves in the college library for anything of interest. I do a modest amount of surfing science sources on the internet. Yet I fall farther and farther behind. The store of reliable human knowledge accumulates exponentially faster than my ability to assimilate.

So I mostly tend my bailiwick. My own little garden of verses. The wispy bits of universe that cling to my life like an aura of places been, things seen, syllables heard. Monarch butterflies, for instance. It was just a few weeks ago I wrote about the monarch migrations and new threats to their existence. The chopping down of their overwintering refuge. The pesticides. The vanishing plants on which they feed and breed. And the mystery- of how a slip of tissue can fly 2500 miles to a place it has never been before.

Now this. They migrate by a Sun compass (no big surprise) mediated by circadian clocks located in their antennae. Off they go, each autumn, with map, compass and clock encoded in their genes. No guide to show them the way, except what they were born with. ATTCTGCCATGC…

That the compass and clock evolved together, leading butterflies from all over eastern North America to the same place in central Mexico, seems a miracle beyond imagining. But I try to imagine it. Because, for the moment, there is no alternative. And this. The Sun compass that guided them south must be reset for the northward journey. It turns out that it is temperature that resets the compass. The chilly temperatures of the Mexican winter swing the needle around to point away from the Sun.

Back to my New England meadows. Now the monarchs have something else to worry about. Global warming.”

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