2012年大学英语六级快速阅读冲刺题（7）
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The Fish and the Forest Few wildlife spectacles in North America compare to the sight of bears gathered along streams and rivers to scoop up spawning (产卵) salmon. The hungry bears have long attracted attention, particularly from fishery managers, who in the late 1940s proposed their broadscale culling in Alaska to reduce the "economic damage" the predators（掠夺者, 食肉动物）might be wreaking on salmon populations. In fact, several sensationalized reports implied that Alaska might fall into "financial and social collapse" unless the bear populations were controlled. Fortunately, common sense came to the rescue, and the bear cull never came about. Scientific interest in the interaction between bears and salmon died down. Recently, however, researchers have discovered a new facet of this relationship, and the finding has radically changed notions about how the salmon, the streams and the bordering woodlands affect one another-and, naturally, notions about how they should be managed. Our own contributions to this work have spanned more than a decade. During this time we have walked hundreds of kilometers along salmon streams, examined tens of thousands of salmon carcasses (动物的尸体), and had too many close encounters with agitated（激动的，不安的）bears. Our findings surprised us: bears actually fertilize the forests, nourishing them by discarding partially eaten salmon carcasses. Not intentionally, of course, but the end result is that these large predators bring valuable marine-derived nutrients, in the form of salmon tissue, to the streamside woodlands, where the uneaten fish provide sustenance（食物, 生计）for an array of animals and plants. The flow of nutrients from ocean to streams to woodlands is an unexpected, even unprecedented, uphill direction for resources to travel. A close look at the life history of the predator and its favorite prey helped us and other scientists piece together how this unusual transfer system operates. (www．Examw。com) Pacific salmon vary in abundance, size and behavior, but all members of this species share the same general life cycle. Young salmon emerge from the gravel in streams or lakes in spring and then, over various periods of time, migrate to the ocean. After living at sea between one and four years, they return to their natal (出生的) streams to spawn and die. The young salmon are quite small when they leave freshwater, weighing from less than 1 gram to about 20 grams, and they are quite big when they return, ranging from 2 to 10 kilograms or more. Consequently, even though most juveniles die at sea, the return migration and death of adult salmon produce a large net flow of nutrients and energy from the ocean to stream and lake ecosystems. 相关资料 |
