Genetically Modified Plants: Monsters or Miracles?
November 30, 1999
The term GMO or genetically modified organism has recently come to designate organisms, especially plants, which have been altered by adding one or a few genes through recombinant DNA techniques. This is now often contrasted with what is called "traditional" plant breeding techniques. The use of recombinant DNA techniques, collectively termed "genetic engineering" has come to be viewed as something altogether new and different from anything that "traditional" plant breeders do. Some even see it as "unnatural" and the potential source of mutant plants that could be harmful to the environment and human health.
Oddly enough, traditional plant breeders are always on the lookout for mutants - perhaps it's worth reminding you that mutation simply means change. The short wheat plants that gave us the Green Revolution were mutants - mutants that yielded much more wheat because the plants were short and sturdy and didn't fall over and produced more seeds. Farmers around the world planted those mutants, growing more wheat than they'd ever grown and feeding more people than the world had ever contained before. These mutants gave the lie to Malthus' prediction, about a hundred years ago, that the number of people in the world would soon outstrip the food supply.
Norman Borlaug, the father of the Green Revolution, had to wait for nature to toss up the right mutation. Today, using recombinant DNA technology and our expanding knowledge of plant genes, we can do it ourselves. This is like the difference between having to depend on a lightening strike for the fire to cook your evening meal and learning how to make matches to be able to make a fire when and where you want it. My point is simply that rDNA technology is another step forward on a human continuum of acquiring and using knowledge to make life easier and food more plentiful.
Now let's step back and examine the world stage on which these steps are being taken. The human population is roughly 6 billion - at least that's the official estimate as of October 12th 1999. At the beginning to the century, there were a billion and a half people on the earth. The number passed 2 billion in 1927, 3 billion in 1960, 4 billion in 1974, and 5 billion in 1987 - and today it's 6 billion, only seconds (on a historical time scale) after it passed the 5 billion mark. Birthrates are coming down everywhere in the world - faster than expected. That's the good news. But the bad news is that we're still adding almost 80 million people to the population every year. This means that there will be another 2 to 4 billion people on the earth before the population stops growing.
We are all increasingly aware of the fragility of our environment. Although we hardly give it a thought, agriculture itself is tremendously destructive ecologically. So we face the dilemma that we must feed a still larger population, yet become better stewards of our environment everywhere in the world. We can only succeed in doing so by knowing more and using that knowledge to make our agricultural practices less destructive and our food more nourishing. When we evaluate the risks and benefits of any particular innovation, such as the use of herbicide resistant crops, we need to evaluate them in the context of what we are already doing.
What are the risks of genetically modified plants? Well - if you're worried about the recombinant DNA techniques, it is already clear that there aren't special risks that result from using the new techniques themselves. By this time, literally billions of genetically engineered organisms have been made and there is not a single report of a monster or a mutant that's out of control. But does this mean everthing's ok and there's nothing to worry about? Not at all. What it means is that the kinds of things that we need to worry about are the kinds of things we are already having to manage. They have to do with the kind of plant and its particular characteristics. There aren't any useful generalizations here.
Let's take one familiar case. Many millions of acres, both in the US and elsewhere, have been planted with cotton that is resistant to a certain kind of major cotton pest, the cotton bollworm. People don't eat cotton plants, so there aren't any human health risks. But even for plants which people eat, adding the toxin doesn't create a health risk, it just adds a little protein - and I mean a little tiny bit - because the protein that makes them resistant is quite toxic to insects but it isn't toxic to people. The good news for the environment is that in 1998, as an example, some 2 million fewer pounds of pesticide were applied to the fields than would have had this been an ordinary cotton crop.
The genetic modification in these plants is that they contain and express an gene from the bacterium Bacillus thurengiensis, aka Bt, that codes for a protein that is toxic to the cotton bollworm. What about the problem of "gene flow?" Well, genes only flow between very closely related plants, because the only way they can get out is through the pollen. But cotton pollen doesn't do a thing for other plants - only very closely related weeds and cotton doesn't have any close relatives in the US. So this isn't an issue for this kind of plant in this country.
What about loss of gene diversity or biodiversity. Concern over losing gene diversity arises because some people think that we now have lots of genetic diversity in our crop plants. We don't. We now grow the best strains on as many acres as we can. GMOs don't change this substantially. Another concern is about the loss of biodiversity. This means different things to different people, but the central concern seems to be that GMOs are so efficient at killing pests that we'll have fields that have no insects left, so the birds will starve. The reverse is true. The Bt plants kill only those insects that munch on them and only the small subset of insects that are sensitive to that particular and very specific toxin, while a broad-spectrum pesticide kills every insect in sight.
But there are risks. The Bt gene is being introduced into many crops in a very short period of time. However we may try, we can't outrun nature forever and insects resistant to the Bt toxin already began to appear simply from the use of the bacterium itself, which we've been using in agriculture and in the control of gypsy moths for many years. So the bottom line is that there are risks - they're mostly economic and none of these risks are unique to GMOs.
Jim Watson, co-discoverer of the structure of DNA, has said that this is the safest technology humans ever invented. To this I would add that it has the potential of being the most environmentally conservative way of increasing the food supply as we struggle to slow the runaway train of human population growth with the slower fixes of education and economic development.
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Nina Fedoroff, Willaman Professor of Life Sciences Director,
Life Sciences Consortium and Biotechnology Institute, The Pennsylvania