NARRATOR：

Now listen to part of a lecture on the topic you just read about.

FEMALE PROFESSOR：

Sure, there’re some benefits to planting genetically modified trees, but are these trees really as great as they first sound?

When you examine the subject closely, there are some serious problems and costs associated with using genetically modified trees.

First, genetically modified trees may be resistant to one particular condition, but that doesn’t necessarily ensure their survival.

Ya see, a typical nonmodified tree population is genetically diverse.

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.

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.

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.

So if the climate changes or a… a new pest invades an area, the genetically modified trees will likely be completely wiped out.

Now as to the second point, there are hidden costs associated with growing genetically modified trees.

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.

Also, after you’ve grown the tree, you can’t just collect the seeds and plant a new tree for free;

by law, you have to pay the company every time you plant.

And finally, genetically modified trees might actually cause even more damage to the local wild trees.

You see, genetically modified trees often grow more aggressively than natural trees do, and genetically modified trees are typically planted among natural trees.

As a result, the genetically modified trees outcompete the native trees for resources, sunlight, soil, nutrients, and water, eventually crowding out the natural trees.