Biocontrol is the use of one species to control the population of a another. It is most commonly employed in agriculture to control crop pests. For instance, if there is an insect that is causing major problems with crops in a certain region, scientists can research biocontrol alternatives. They will look for other insects that eat or parasitize the pest insect, or different bacterial or fungal diseases that can infect and thus destroy the pest. A commonly-cited successful example of biocontrol is the control of cottony cushion scale, a pest on citrus trees in California, using a special type of ladybug imported from Australia.
Often biocontrol entails bringing organisms from one part of the world to another, which brings up many biosafety concerns. It is difficult to predict the negative effects that these new organisms may have on the local ecosystem, beyond the positive impact of controlling the crop pest you're targeting. Whenever you introduce a foreign organism into an ecosystem, it is possible that it will reproduce and spread uncontrollably, because you've taken it away from whatever factors keep its population at a reasonable level in its nattive range. If this happens, the introduced species may displace other, native species, or become a pest in its own right. Something like this has happened with the Asian multicolored ladybeetle which, while it admittedly controls aphids as it was originally supposed to, has become a nuisance to homeowners in much of the US, and is displacing some native ladybug species. With careful
planning, as is normally done when a biocontrol agent is released to fight
against a crop pest, the new species is analyzed and tested extensively
beforehand to make sure that the new effect it has on the environment
will be mainly limited to controlling the target pest (which itself
usually happens to be a species that was inadvertently introduced
Biocontrol efforts are not the only cause of invasive species propagation. Species like the nutria in New Orleans, or kudzu in the US South, or the Asian carp in the Mississippi river, were originally brought to the US for commercial reasons (for hides, erosion control, and pond cleaning, respectively), and they have since multiplied wildly. Probably the most common source of invasive introductions is unintentional--foreign species hitch a ride on clothes, bilge water, pallet wood, or any number of other ways, and become established somewhere they shouldn't be. Again, many of the major crop pests are invasive species, which is why it is often necessary to seek biocontrol agents abroad, where the pest is originally from.
Genetic engineering has a few things in common with biocontrol. Perhaps most notably, it is one technological approach among many that may have a positive impact on agriculture. People get excited when they first hear about biocontrol, because when it works, it is one of the best, least toxic, most durable, least expensive ways of dealing with crop pests. Nevertheless, biocontrol's applications have been quite limited up until now, so these days it is not a major focus of agronomy funding or research. It turns out that it is just not that simple to find a single species that can effectively control a crop pest.
Likewise, genetic engineering has until now not found many practical applications. Granted, the insertion of glyphosate resistance and natural insecticides into corn, soybeans, cotton, and canola have been very lucrative technologies that caught on across the US and other parts of the world. But these are basically just two marketable discoveries in the last 20+ years, that have since been revisited, riffed on, and tweaked. Scientific fashion is still smitten with the idea of transgenics, because they sound really cool, but when you weigh the overwhelming dominance of transgenic research in the overall agricultural research portfolio over these decades, just two marketable ideas is not a great return to the R&D buck. I believe that, as the ag research community gets over the initial wow-factor of transgenic approaches, we will gradually come to see them as one rather limited tool at our disposal (as we view biocontrol), as opposed to the principal avenue we should be investigating. This is a good thing, because pouring so many resources into just one area of research inherently means that you are depriving other, perhaps equally worthy avenues of inquiry.
Another commonality between biocontrol and genetic engineering is the question of biosafety. Scientists and the general public clearly see the undesireability of losing a native species displaced by an introduced biocontrol agent, even if there is no clear economic impact from this loss. For instance, if Ilinois's native ladybeetles are disappearing and their ecological niche is taken up by the Asian ladybeetles, no one will likely lose any money, and frankly, the ecosystem will probably not suffer any major damage, since one ladybeetle species can perform the same ecological functions as another. But nevertheless, few would argue that the loss is unimportant--that is one species, one bit of diversity and wonder and uniqueness, that has disappeared from the Earth, never to come back. I would argue the same for the infiltration of a foreign gene into a general crop population. If a Bt transgene gets into a traditional sweetcorn variety that has been passed down to you by your grandparents, you probably won't notice the differencce. Your corn will keep growing fine and tasting the same as it always has, because it is still 99.99% the same as before. But even if the economic or the ecological performance of the corn remains the same, it is clear that something has been changed; something will be lost. Call it purity, or integrity, or whatever else you want--there will have been a fundamental change imposed on you and your corn, through no desire of your own. Inserting a novel gene into a living organism is not to be
taken lightly, because once this gene has entered the general
population, you can never totally remove it. It is like a more
insidious form of introducing a novel species to an ecosystem; there
have been successful (albeit costly and difficult) eradication campaigns of invasive species after
they've been introduced, but it would be almost impossible to eradicate a
specific allele from a plant population once it has spread. If
we believe we should be careful, and especially wary of our own complacence and hubris,
in the case of a new species introduction that can be reversed, we should be all the more cautious with a gene
transfer that cannot be undone.
So here we have one ethical, not scientific or economic, reason to avoid or at least minimize the planting of transgenic crops: inserting a novel, foreign gene into a genome is akin to introducing a foreign species into a native ecosystem. It creates an irreparable change in the essence of the system, and this is something that should not be done blithely. There is some recognition of this principle even in mainstream promotion of transgenics. There seems to be a relatively strong consensus that transgenic crops should be kept out of the zones of origin and diversity for a given crop, such as corn in Mexico or wheat in the Fertile Crescent. I believe the thinking here is that, even if the transgene shows no clear negative effects on people or the environment, common sense precautions should preclude us from doing anything that might spread something so fundamentally novel throughout the natural stocks of genetic diversity for a given species.
I think that this instinct to avoid introducing transgenes into biodiversity hotspots is a sound one. The problem is that these diversity hotspots are not limited to the seven small geographical regions traditionally considered as crop centers of origin. Every traditional field or garden is a biodiversity hotspot. I see this very clearly in Colombia, where a farmer may grow ten different traditional varieties of potato on the margins of his commercial potato monoculture, and even within any one of these varieties there exists much phenotypic diversity. But you don't have to go that far afield--if your neighbor participates in Seed Savers Exchange in the US, or your grandmother has three different types of collard greens whose seeds she got from her grandmother, or the country roads outside your town have lots of abandoned, semi-wild apple trees from old farmsteads, all of you are witnessing areas of important crop genetic diversity. If this is the case, then that aversion to introducing transgenes into a center of origin for a given crop would extend over most of the planet.
Beyond and concurrent to this idea of not introducing transgenes into crop biodiversity hotspots, we have to consider the question of sovereignty and free will. Everyone has the right to say they don't want a certain crop variety in their fields--no one in the US would propose going into people's gardens and forcing them to plant only yellow tomatoes, or honeydew melons but not cantaloupes. We in the US are particularly insistent on our right to control our own space and our own decisions, but I think this is a universal value. We see it clearly when it comes to other technologies. The larger US society allows the Amish or any other group or individual to decide which technologies they will adopt or not allow in their lives. Despite the immense, obvious benefits to hooking your house to the electric grid, no one would propose forcing the Amish to use electricity. Even in the case of vaccination, where non-adoption by one person has a negative effect on the collective and should thus perhaps not be a protected right, most people would never advocate forced vaccination.
As with vaccination, which involves living organisms that spread beyond just the person making a given decision, things get a bit complicated when we're talking about plants and semi-natural systems like a garden or a farm field. You can't exclude the pollen from neighbors' plants from coming onto your field, and normally you have no right to, since that's how nature works. An engineered gene, on the other hand, is not a product of natural creation but of human artifice, and I should be able to decide whether that goes in my crop or not (especially since I could be sued if it is, as is the case with our prevailing laws allowing patentable transgenes).
Hence even if everyone around me were to agree that a particular transgene were a great thing, and even if my paltry little garden were not located in a biodiversity hotspot of any major concern, I would argue that it is still my right to insist that that gene not be introduced into my crops unless I want it to be. That is part of the free will and sovereignty that should be my birthright
Now I'm not so naive or polemical as to think that free will is an absolute. We are constantly ceding little bits of our sovereignty to the collective, and it must be this way unless we wish for a violent, chaotic society, each living as an island unto him- or herself, oblivious to our common interests. In theory, almost every country in the world reserves the right to call on its citizens to give their lives, the very essence of their personal sovereignty, in defense of the collective. But any time we give up some degree of our freedom, or call on others to do so, it must be with very good cause. The public will not support an unjust war (at least not in the long run); your neighbors won't respect your right to have a live dog if the dog keeps messing up their stuff or attacking their kids; even your house and property can be taken from you if the government goes through established, fair processes of eminent domain and can reasonably convince everyone else that it's for a just cause.
I believe the same principles should apply to transgenics. We should weigh the potential benefits of any transgene with the inherent affront it represents to the integrity of the natural world, or the free will of humanity. I haven't ever heard of anyone who objects to the treatment of diabetes with synthetic insulin. This insulin is produced by either E. coli bacteria or yeast that have been genetically engineered to make human insulin. On the one hand, the risks of such synthesis seem low, since it is confined to laboratories and factories, and the payoff seems high, because it saves millions of human lives. The benefit and the cause seem to be so positive and just that they trump any concerns we have about playing with human genes, or the low possibility of escape of this modified yeast into breweries and bakeries. On the other hand, few serious scientists would consider putting glow-in-the-dark genes into a human embryo (or really doing any experimentation with human embryos, for that matter), because the fact that a glow in the dark person would look cool is no justification for the ethical breach represented by experimenting with human life.
The problem is that
most transgenics have not given humanity at large any stellar advantages over
conventionally-bred crop varieties. As far as I know, the European corn
borer that Bt corn was first designed to manage, was not that serious
of a pest in much of the Corn Belt. Your fields had to be really
infested before treatment was justified. Conversely, the advent
of Bt varieties to fight Western corn rootworm was indeed a major breakthrough in many ways. It drastically reduced the use of
pesticides to fight this pernicious pest, and this is a laudable
achievement. That said, growers could have avoided these
chemicals in the first place with sensible crop rotation cycles of 3
years or more, instead of planting corn year after year. The spread
of no-till farming is definitely a good thing, and glyphosate-resistant
crops happened to be the way it played out, though the use of herbicide to avoid midseason cultivation could have come about through other channels. I don't see why the
idea of no-till couldn't have been pursued with the mix of selective
herbicides that farmers were using before Roundup. Hell, Clearfield imazapyr-resistant corn was a conventional-bred competitor to
glyphosate-resistance for a while, until the market dominance of
the Roundup-Ready trait asserted itself. That is to say that VHS won out over Betamax, but that was just an
idiosyncracy of the market, not an indication of one technology's being objectively
better than the other. In short, transgenics have thus far
shaved some costs and some thought off of the management of corn, beans,
cotton, and canola, but they haven't changed the way we do farming. If
anything, transgenics have further cemented a chemical-intensive, thought-scarce agriculture
that has some pretty profound inherent problems. If I'm right, then the net benefit to society of the commercial application of transgenic crops has not been that impressive thus far, and certainly has not created a clear case to override any of the possible ethical objections to transgenics I've raised above.