英語聽力：自然百科 Rocky mountain bio lab wildflowers 溫室效應(yīng)

In the Rocky Mountains of Central Colorado, the forces of nature create a landscape of alpine lakes, high-altitude ponds teeming with life and mountain meadows bursting with wild flowers. It is amidst these beautiful wildflower fields that one scientist has already found alarming evidence about the potential impact of global warming. John Hart, a professor of Environmental Science at the University of California, Berkley, runs an experiment to determine what would happen if the temperature was just three degrees warmer here year around, like the forecasted effect of global warming.

“That heating effect will induce dramatic effects on these subalpine meadows, causing loss of plant seed we especially value here, the flowering plants.”

John Hart has come here each summer since the 1970s, examining factors affecting life in this fragile ecosystem.

“This heating is actually quite subtle. We are not heating a lot. It’s only a few degrees, but it’s causing the flowering plants to produce fewer flowers and to grow less abundantly.”

His setup is relatively simple. Low-power electric heaters suspended above a mountain meadow heat the ground and the plant life beneath, three degrees warmer than the surrounding area. The heaters are automatically and precisely controlled, they have been on constantly, day and night, winter, spring, summer and fall since 1991. In his global warming experiment, he suspended heaters in a grid pattern to create heated plots, then unheated plots, back and forth, so he can judge the effects side by side. The difference, three degrees of separation makes in flowers and sagebrush, is easy to see.

“They suck juices out of the plant.”

In the unheated natural area, sagebrush is a source of moisture for an army of thirsty insects. They keep sagebrush under control.

“So they have little mouthpieces that can suck away at the nutrient.”

But just a few feet away, sagebrush under the heater grows far better with fewer bugs.

“...much more rapidly, we found that the heating is causing profuse growth of the sagebrush.”

While that’s good for the sagebrush; it’s not good for its plant neighbors. Flowers feel the effect too. In natural areas, flowers grow thick as they always do here, but a few feet away, where it’s three degrees warmer, flowers are not as abundant.

“The meadows, instead of looking lush and strewn with flowers, are now actually rather arid.”

If global warming, or long-term climate change, does increase the year-around temperature here just a few degrees, John Hart predicts, in decades to come, flowers could be crowded out by sagebrush.

“Global warming is more than just an ecological catastrophe; it would be a human catastrophe in all of its dimensions.”