(09四川E)
All too often, a choice that seems sustainable (可持续的) turns out on closer examination to be problematic. Probably the best example is the rush to produce ethanol (乙醇) for fuel from corn. Corn is a renewable resource — you can harvest it and grow more, almost limitlessly. So replacing gas with corn ethanol seems like a great idea.One might get a bit more energy out of the ethanol than that used t make it, which could still make ethanol more sustainable than gas generally, but that's not the end of the problem. Using corn to make ethanol means less corn is left to feed animals and people, which drives up the cost of food. That result leads to turning the fallow land一including, in some cases, rain forest in places such as Brazil 一into farmland, which in turn gives off lots of carbon dioxide (C02) into the air. Finally, over many years, the energy benefit from burning ethanol would make up for the forest loss. But by then, climate change would have progressed so far that it might not help.You cannot really declare any practice (“sustainable” until you have done a complete life-cycle analysis of its environmental (环境的) costs. Even then, technology and public policy keep developing, and that development can lead to unforeseen and undesired results. The admirable goal of living sustainably requires plenty of thought on an ongoing basis.
拜托大家了,好的继续追加。
千万不要用翻译器。 用了也不采取。 要自己翻译。
参考资料:原创回答团