Creeping Toward Permanent Drought

Scientific American

Both trees and climate models are telling us the same frightening story

Trees killed by drought in Bakersfield, California. Credit: Ashley Cooper Getty Images

I left California in the middle of a drought. The hills framing the 280 from the city to Palo Alto turned brown in the summer, as they always did, and then stayed brown through the winter. The pleasant seventy-degree air began to feel oppressive, the glorious blue sky a source of inchoate guilt. I lived in Oakland, by a cemetery on a hill. The winding paths past angel-topped mausolea and modest age-blacked gravestones were framed by a line of sweet gums, peppered with cypress, redwood, and olive. The smell—a peppery sweetness, pine without Christmas—is what I remember when I think of home.

I now live in New York City, where trees are considered suspicious, not allowed to congregate in groups outside the designated parks. The few on my street are framed by small cages to keep the local dogs away. The effect is pathetic, almost comic, a tiny prison for a tall defiant thing. The largest tree I have seen in New York is dead and in the natural history museum. It is an enormous stump of a California sequoia, each ring a record of a life that began twenty generations before the birth of the logger who ended it.

The trees in New York, and the city too, are fed by moisture carried from the Gulf of Mexico or the Atlantic. There is no dry season, just a scatter of rain and snow spread evenly on top of the year. California rainfall, though, beats with the erratic rhythm of the tropical Pacific. There, the long spine of South America dredges cold water from the depths of the ocean, upwelling to form a permanent pool of cold water that extends into the west, pushed there by the trade winds. The cold water sloshes back and forth, the winds that drive it pulse to their own beat, and the result of the dance is, in some years, a phenomenon of warmer-than-usual water: the Christ Child, El Niño. When he visits, California can expect a rainy winter. When the opposite conditions prevail—La Niña—it’s drought.


Author: Willem Van Cotthem

Honorary Professor of Botany, University of Ghent (Belgium). Scientific Consultant for Desertification and Sustainable Development.

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