|
2013年6月英语六级真题阅读理解Section B原文+答案解析 Section B Directions: There are 2 passages in this section. Each passage is followed by some questions or unfinished statements. For each of them there are four choices marked A), B), C) and D). You should decide on the best choice and mark the corresponding letter on Sheet 2 with a single line through the center. Passage Two Usually when we walk through the rain forest we hear a soft sound from all the moist leaves and organic debris on the forest floor, says ecologist Daniel Nepstad. Now we increasingly get rustle and crunch. Thats the sound of a dying forest. Predictions of the collapse of the tropical rain forests have been around for years. Yet until recently the worst forecasts were almost exclusively linked to direct human activity, such as clear- cutting and burning for pastures or farms. Left alone, it was assumed, the worlds rain forests would not only flourish but might even rescue us from disaster by absorbing the excess carbon dioxide and other planet-warming greenhouse gases. Now it turns out that may be wishful thinking. Some scientists believe that the rise in carbon levels means that the Amazon and other rain forests in Asia and Africa may go from being assets in the battle against rising temperatures to liabilities. Amazon plants, for instance, hold more than 100 billion metric tons of carbon, equal to 15-years of tailpipe and chimney emissions. If the collapse of the rain forests speeds up dramatically, it could eventually release 3.5-5 billion metric tons of carbon into the atmosphere each year making forests the leading source, of greenhouse gases. | 
