单项选择题

Are genetically modified crops an environmental dream come true or a disaster in the making Scientists are looking for answers.
The world seems increasingly divided into those who favor genetically modified (GM) foods and those who fear them. Advocates assert that growing genetically altered crops can be kinder to the environment and that eating foods from those plants is perfectly safe. And, they say, genetic engineering—which can induce plants to grow in poor soils or to produce more nutritious foods— will soon become an essential tool for helping to feed the world’s burgeoning population. Skeptics contend that GM crops could pose unique risks to the environment and to health—risks too troubling to accept smoothly. Taking that view, many European countries are restricting the planting and importation of GM agricultural products. Much of the debate hinges on perceptions of safety. But what exactly does recent scientific research say about the hazards The answers, too often lost in reports on the controversy, are served up in the pages that follow.
Two years ago in Edinburgh, Scotland, eco-vandals stormed a field, crushing canola plants. Last year in Maine, midnight raiders hacked down more than 3,000 experimental poplar trees. And in San Diego, protesters smashed sorghum and sprayed paint over greenhouse walls.
This wide-ranging outrage took aim at genetically modified crops. But the protests backfired: all the destroyed plants were conventionally bred. In each case, activists mistook ordinary plants for GM varieties.
It’s easy to understand why. In a way, GM crops—now on some 109 million acres of farmland worldwide—are invisible. You can’t see, taste or touch a gene inserted into a plant or sense its effects on the environment. You can’t tell, just by looking, whether pollen containing a foreign gene can poison butterflies or fertilize plants miles away. That invisibility is precisely what worries people. How, exactly, will GM crops affect the environment—and when will we notice
Advocates of GM, or transgenic crops, say the plants will benefit the environment by requiring fewer toxic pesticides than conventional crops. But critics fear the potential risks and wonder how big the benefits really are. "We have so many questions about these plants," remarks Guenther Stotzky, a soil microbiologist at New York University. "There’s a lot we don’t know and need to find out. "
As GM crops multiply in the landscape, unprecedented numbers of researchers have started fanning into the fields to get the missing information. Some of their recent findings are reassuring; others suggest a need for alertness.
According to the advocates, which of the following is NOT the advantage of GM plants