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 laser engraver 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 placidly. Taking that view, many European countries are restricting the planting and importation of GM agricultural products. Much laser cutting machine 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 laser cutter laser machine more than 3,000 experimental poplar trees. And in San Diego, protesters smashed sorghum and sprayed paint over greenhouse walls.
This far-flung outrage took laser cutter 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 laser engraving machine 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 laser cutting equipment 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 laser cutting system 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 cutting plotter 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 vigilance.

Fewer Poisons in the Soil?
Every year u.s. growers shower crops with an estimated 971 million pounds of vinyl cutter pesticides, mostly to kill insects, weeds and fungi. But pesticide residues linger on crops and the surrounding soil, leaching into groundwater, running into streams and getting gobbled up by wildlife. The constant chemical trickle is an old worry for environmentalists.
In the mid-1990s agribusinesses laser cutting machine began advertising GM seeds that promised to reduce a farmer's use of toxic pesticides. Today most GM crops－mainly soybean, corn, cotton and canola－contain genes enabling them to either resist insect pests or tolerate weed-killing herbicides. The insect-resistant varieties make their own insecticide, a property meant to laser cutter reduce the need for chemical sprays. The herbicidetolerant types survive when exposed to broad-spectrum weed killers, potentially allowing farmers to forgo more poisonous chemicals that target specific weed species. Farmers like to limit the use of more hazardous pesticides when they can, but GM crops also hold appeal because they simplify operations (reducing the laser cutter frequency and complexity of pesticide applications) and, in some cases, increase yields.
But confirming environmental benefit is tricky. Virtually no peer-reviewed papers have addressed such advantages, which would be expected to vary from plant to laser engraver plant and place to place. Some information is available, however. According to the U.S. Department of Agriculture, farmers who plant herbicidetolerant crops do not necessarily use fewer sprays, but they do apply a more benign mix of chemicals. For instance, those who grow herbicide-tolerant soybeans typically avoid the laser engraver most noxious weed killer, turning instead to glyphosate herbicides, which are less toxic and degrade more quickly.
Insect-resistant crops also bring mixed benefits. To date, insect resistance has been provided by a gene from the soil bacterium Bacillus thuringiensis (Bt). This gene directs cells to laser engraving machine manufacture a crystalline protein that is toxic to certain insects－especially caterpillars and beetles that gnaw on crops－but does not harm other organisms. The toxin gene in different strains of B. thuringiensis can affect different mixes of insects, so seed makers can select the version that seems best suited to a particular crop.
Of all the crops carrying Bt genes, cotton has desktop laser engraver brought the biggest drop in pesticide use. According to the Environmental Protection Agency, in 1999 growers in states using high amounts of Bt cotton sprayed 21 percent less insecticide than usual on the crop. That's a “dramatic and impressive” reduction, says Stephen Johnson, an administrator in the EPA's Office vinyl cutter of Pesticide Programs. Typically, Johnson says, a farmer might spray insecticides on a cotton field seven to 14 times during a single growing season. “If you choose a Bt cotton product, you may have little or no use for these pretty harsh chemicals,” he notes. Growers vinyl cutter of Bt corn and potatoes report less of a pesticide reduction, partly because those plants normally require fewer pesticides and face fluctuating numbers of pests.
Defining the environmental risks of GM crops seems even harder than calculating their benefits. At the moment, public attention is most trained on Bt crops, thanks to several cutting plotter negative studies. Regulators, too, are surveying the risks intensely. This spring or summer the EPA is expected to issue major new guidelines for Bt crops, ordering seed producers to show more thoroughly that the crops can be planted safely and monitored in farm fields.
In the face of mounting consumer craft cutter concern, scientists are stepping up research into the consequences of Bt and other GM crops. Among their questions: How do Bt crops affect “nontarget” organisms－the innocent bugs, birds, worms and other creatures that happen to pass by the modified plants? Will GM crops pollinate nearby plants, casting their genes into the wild to create superweeds mini laser engraver that grow unchecked? What are the odds that the genetically engineered traits will lose their ability to protect against insects and invasive weeds, leaving GM plants suddenly vulnerable?
At What Cost to Wildlife?
In 1998 a swiss study provoked widespread worry that Bt plants can inadvertently harm unlucky creatures. In this laboratory experiment, green lacewing caterpillars proved more likely to die after eating European corn-borer caterpillars that had fed on Bt corn instead of regular laser cutting corn. The flames of fear erupted again a year later, when Cornell University entomologist John Losey and his colleagues reported that they had fed milkweed leaves dusted with Bt corn pollen to monarch butterfly larvae in the lab and that those larvae, too, had died.
“That was the straw that broke the camel's back,” says David Pimentel, also laser cutting an entomologist at Cornell. Suddenly, all eyes turned to the organisms munching GM plant leaves, nipping modified pollen or wriggling around in the soil below the plants－organisms that play vital roles in sustaining plant populations. Another alarming study relating to monarch butterflies laser engraving appeared last August.
But the lab bench is not a farm field, and many scientists question the usefulness of these early experiments. The lab insects, they note, consumed far higher doses of Bt toxin than they would outside, in the real world. So researchers have headed into nature themselves, measuring the toxin in laser engraving pollen from plots of GM corn, estimating how much of it drifts onto plants such as milkweed and, finally, determining the exposure of butterfly and moth larvae to the protein. Much of that work, done during the 2000 growing season, is slated to be reported to the EPA shortly.
According to the agency, however, preliminary studies evaluating the two most common Bt corn plants (from Novartis and Monsanto) already indicate laser tube that monarch larvae encounter Bt corn pollen on milkweed plants－but at levels too low to be toxic. What is toxic? The EPA estimates that the insects face no observable harm when consuming milkweed leaves laden with up to 150 corn pollen grains mini cnc router per square centimeter of leaf surface. Recent studies of milkweed plants in and around the cornfields of Maryland, Nebraska and Ontario report far lower levels of Bt pollen, ranging from just six to 78 grains of Bt corn pollen per square centimeter of milkweed leaf surface. “The weight of the evidence suggests Bt cnc router corn pollen in the field does not pose a hazard to monarch larvae,” concludes EPA scientist Zigfridas Vaituzis, who heads the agency's team studying the ecological effects of Bt crops.
But the jury is still out. “There's not much evidence to weigh,” notes Jane Rissler of the Union of Concerned Scientists. “This issue cnc router of nontarget effects is just a black hole, and EPA has very little good data at this point to conclude whether the monarch butterfly problem is real, particularly in the long term.”
In an EPA meeting on GM crops last fall, Vaituzis acknowledged the lack of long-term data on Bt crops and insect populations. Such studies “require more time than has been available since the registration of Bt crops,” Vaituzis remarked. The EPA, he added, continues to collect Bt cnc engraver crop data－but so far without evidence of “unreasonable adverse effects” on insects in the field.
Seeding Superweeds?
Worries about the flow of genes from the original plant to others also surround GM crops. Unwitting insects or the right wind might carry GM crop pollen to weedy plant relatives, fertilizing them. And if that happens, the newly endowed plants could break cnc engraver ecological rank, becoming “superweeds” that are unusually resistant to eradication by natural predators or pesticides. Scientists have stopped asking if such gene flow is possible. “In many cases,” says Cornell ecologist Allison Power, “we know gene flow will occur. The question now is, What will the consequences be?”
So far no scientific studies have found evidence cnc engraving machine of GM crops causing superweeds, and a 10-year study reported in Nature in February found no weedlike behavior by GM potatoes, beets, corn or canola planted in England. But worrisome anecdotes have appeared. Canadian farmers, in particular, have described GM canola escaping from farm fields and invadingwheat crops like a weed. This canola also resisted pesticide sprays.
Power's studies of gene flow from virus-resistant GM plants cnc engraving machine give further reason for precaution. For now, virus-resistant crops stake a small share of the GM landscape, but they are likely to become more prevalent, particularly in the developing world. Power investigates gene flow in cultivated grain crops－ wheat, barley and oats－engineered to contain genes that make the plants resistant to the barley yellow dwarf virus (which damages some 100 grass species). These GM grain crops cnc wood router could be on the market within the next decade.
Power's work, carried out in the laboratory, indicates that wild oats－a weedy relative of cultivated oats－can “catch” the genes conferring resistance to barley yellow dwarf virus. If that happened in the field, she says, wild oats might run amok in the western U.S., outcompeting native grasses with kudzu-like intensity. Every GM crop, Power cautions, brings its own environmental cnc woodworking router personality and its own risks.
In the U.S., at least, landscape logistics make it rather unlikely that herbicide-tolerant or Bt crops will spread their biotech genes to weeds. That's because the GM crops sown in this country have no close relatives in the regions where they grow; most plants can pollinate others only if the recipients and the donors have certain features in common, such as the same chromosome number, life cycle or preferred habitat. A known cnc wood working router exception to the “no relatives” rule in the U.S. is wild cotton growing in Hawaii and southern Florida, which, by virtue of its unusual similarity to GM cotton, can accept the GM pollen. To wood engraver separate the wild and biotech plants from each other, the EPA has ordered companies not to sell GM cotton south of Florida's Interstate 60 or in Hawaii.
But it may prove harder to avoid creating superweeds outside North America, where weedy relatives of cultivated crops are plotter common. Wild cotton, for instance, creeps past the Florida Keys, across the Gulf of Mexico and into Mexico. In South America, a weedy corn relative, teosinte, dresses the edges of domesticated cornfields. Either plant would readily accept the pollen from a GM relative. Indeed, scientists say, GM crops in many countries could end up growing near their ancestral plants－and sharing more cnc machine than the sunshine overhead. “Almost every crop has weedy relatives somewhere in the world,” says Stephen Duke, a USDA plant physiologist in Oxford, Miss. “How do you keep GM crops out of places where they're not supposed to be?”
Taking Refuge
Finally, one risk follows GM crops wherever they're wood cnc router planted: evolution. Over time, insect pests and weeds can become resistant to killing by routine chemical sprays. The same is bound to happen in the biotech age: eventually, impervious insects will munch away on GM insect-resistant plants, and the weeds surrounding herbicide-tolerant crops will shrug off the woodworking cnc router herbicide of choice. “Agriculture is an evolutionary arms race between plant protections and pests,” comments botanist Jonathan Wendel of Iowa State University. “And GM crops are just one more way that we're trying to outsmart pests－temporarily.”
To keep weeds vulnerable to herbicides, Monsanto and other companies urge growers to use the sprays responsibly, only when necessary. To slow insect resistance to the Bt toxin, the EPA requires Bt crop growers to set aside some part of their farmland for crops that have not CNC Machining Center been genetically modified. These “refuges” may be a corner of a field outside a Bt crop, for instance, or rows of standard plants that break up a Bt plot. Inside the refuges, insects that have acquired some Bt resistance breed with those that have not, diluting the resistance trait.