原文已被隐藏，你可用 快捷键 - 或点击 显示原文 按钮来查看原文
第一段
1 .Now listen to part of a lecture on the topic you just read about.
该句暂无译文！
第二段
1 .Sure, there are some benefits to planting genetically modified trees, but, are these trees really as great as they first sound?
该句暂无译文！
2 .When you examine the subject closely, there are some serious problems and costs associated with using genetically modified trees.
该句暂无译文！
第三段
1 .First, genetically modified trees may be resistant to one particular condition, but that doesn't necessarily ensure their survival.
该句暂无译文！
2 .You see, a typical non-modified tree population is genetically diverse.
该句暂无译文！
3 .That means that for most threatening conditions, or climates, insects and other pests, whatever, there will be at least some individual trees of any given species of tree that are resistant.
该句暂无译文！
4 .So even if most of one kind of tree are killed, those few resistant ones will survive and ensure the survival of that species of tree.
该句暂无译文！
5 .But genetically modified trees are genetically much more uniform.
该句暂无译文！
6 .So if they're exposed to an environmental challenge they haven't been designed for, they'll all die.
该句暂无译文！
7 .So if the climate changes, or a new pest invades an area, the genetically modified trees will likely be completely wiped out.
该句暂无译文！
第四段
1 .Now as to the second point, there are hidden cost associated with growing genetically modified trees.
该句暂无译文！
2 .You see, the company that genetically modify the tree tends to charge tree farmers much more for its seeds than un-modified tree seeds would cost.
该句暂无译文！
3 .Also, after you've grown the tree, you can't just collect the seeds and plant a new tree for free.
该句暂无译文！
4 .By law, you have to pay the company every time you plant.
该句暂无译文！
第五段
1 .And finally, genetically modified trees might actually cause even more damage to the local wild trees.
该句暂无译文！
2 .You see, genetically modified trees often grow more aggressively than natural trees do.
该句暂无译文！
3 .And, genetically modified trees are typically planted among natural trees.
该句暂无译文！
4 .As a result, the genetically modified trees out-compete the native trees for resources, sunlight, soil, nutrients, and water, eventually crowding out the natural trees.
该句暂无译文！