When provided with continuous nourishment, trees, like people, grow “complacent”—the word tree-ring
scientists use to describe trees like those on the floor of the Colorado River Valley, whose roots tap into thick
reservoirs of moist soil. Complacent trees aren’t much use for learning about climate history, because they pack
on wide new rings of wood even in dry years. To find trees that feel the same climatic pulses as the river, trees
whose rings widen and narrow from year to year with the river itself, scientists have to climb up the steep,
rocky slopes above the valley and look for gnarled, ugly trees, the kind that loggers ignore. For some reason
such “sensitive” trees seem to live longer than the complacent ones. “Maybe you can get too much of a good
thing,” says Dave Meko, a tree-ring scientist who has been studying the climate history of the western United
States for decades. Tree-ring fieldwork is hardly expensive, but during the relatively wet 1980s and early ’90s,
Meko found it difficult to raise even the modest funds for his work. “You don’t generate interest to study
drought unless you’re in a drought,” he says. 【題組】48 Why aren’t complacent trees good for studying climate history?
(A) Their rings are too narrow. (B) They are not well-nourished.
(C) They do not reflect genuine climate change. (D) They are reserved for loggers for good prices.
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