The Bullhead Queen: A Year on Pioneer Lake

The Green Season

The Green Season 137 W hen I look out over the meadow this August morning, the landscape is washed almost entirely in green. The variety of hues is dazzling. There’s the lawn, which can only be described as “grass green,” and the two maples with their three-pointed, hand-like leaves that are still in sprightly summer verdure. The many herbaceous plants of the meadow are beginning to add some golden tones to the palette, and what once was bright and true is more faded and mature, jaundiced, olive and ochre. All too soon the vibrant scene will be colored by the warm yellows of autumn, but this week we still bask in the green season. Of all the sunlight emitted by the glowing orb that forms the center of our solar system, only a fraction of the spectrum is green. Just a small portion of the sun’s light, in fact, actually reaches the earth’s surface. The highest-energy light rays, gamma and X rays, and most ultraviolet rays hit the earth’s atmosphere and bounce back into space. The longest rays penetrate the atmosphere—that insulating blanket that wraps the planet—and warm its surface. We call them “infrared,” and a nonphysicist might be best acquainted with them in everyday life, when staying at a ritzy hotel, where such rays are often used as overhead heaters in bathrooms. Of more significance, perhaps, in our lives is the narrow band of rays that animals on earth can see, the ones to which they have evolved sense organs. We call it “visible light,” and it is only about 14 percent of all the solar radiation that comes through the atmosphere. I used to think it was amazing that our eyes were evolved to see light that reaches the earth rather than the wavelengths that don’t. What a happy coincidence! But think about it: obviously, animals wouldn’t evolve a sense organ to perceive something that isn’t there. The shortest wavelengths we perceive are violet, the longest are red. Somewhere in the middle, at a length of about 5,400 angstroms, is what is lighting up my room, green light. It is the hue to which the human eye is most sensitive. The greenness of the summer world is most striking in the spring, when color returns after a winter spent in monochrome . One April, I spent a week in Louisiana, paddling the bayou outside of New Orleans. I had never experienced the terrain of the Mississippi delta, with its broad sweeping grasses and subtropical palms. My eyes were accustomed to Minnesota’s grays and whites, and on my first morning there, Louisiana seemed unbelievably lush. We had arrived in the area after dark, and I still vividly recall the initial splendor , stepping out into sunshine and beholding an emerald field of sugar cane. “This is life!” I thought. Had I been dead all winter? Then after a few days, I boarded a plane to come home. The day was clear, and from my window seat I watched the planet’s surface below. So incredibly green as we took off and circled the city, then more tentatively green as we headed north. By Iowa, I could see snowy patches: Dorothy returning to Kansas. Doesn’t it seem odd that we live in such a narrow band of the electromagnetic spectrum? Even discounting the large part of the output that bounces back into space, those waves around 5,400 angstroms are a pretty small minority of the 138 The Green Season wavelength world. Yet we are so enmeshed in greenness that we hardly think how strange this must be. To us, to almost all animals, greenness is life, greenness is food and protection and nest material. Greenness means plants, the essential Other in our lives. There is a paradox embedded in this green world. What seems profligacy—so much green—is actually efficiency. Green is one of the few wavelengths that plants do not use. Green light bounces off their tissues—that’s why they appear green. The ecosystems of the earth run on sunlight. It is the ability of green plants to take the sun’s radiant energy and change it into other forms that makes the great web of life possible. Our human bodies, all other animal bodies, run on the fuel of food, measured in calories, and ultimately made by plants. The wavelengths...