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1段
1 .<-NARRATOR:->Now listen to part of a lecture on the topic you just read about.
该句暂无译文！
第2段
1 .<-FEMALE PROFESSOR:->Sure, there’re 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3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 .Ya see, a typical nonmodified tree population is genetically diverse.
该句暂无译文！
3 .That means that for most threatening conditions—poor climate, 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, 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！
6 .So if the climate changes or a… a new pest invades an area, the genetically modified trees will likely be completely wiped out.
该句暂无译文！
第4段
1 .Now as to the second point, there are hidden costs associated with growing genetically modified trees.
该句暂无译文！
2 .You see, the company that genetically modified the tree, tends to charge tree farmers much more for its seeds than unmodified 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5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, and genetically modified trees are typically planted among natural trees.
该句暂无译文！
3 .As a result, the genetically modified trees outcompete the native trees for resources, sunlight, soil, nutrients, and water, eventually crowding out the natural trees.
该句暂无译文！