Biodiversity can be defined as a wide variety of living organisms in their natural environment. Today most societies are aware of activities that threaten biodiversity and are acting to reduce the risks. Although critics of Genetically Engineered Food (GE food) claim that the products of biotechnology threaten biodiversity, almost ten years of commercial growing experience says something different. It is becoming very clear that growing GE crops helps reduce the impact of agriculture around the world.
Every year hundreds of millions of pounds of organophosphate insecticides are sprayed on crops. These broad-spectrum insecticides kill virtually every insect on contact. The run-off from the sprays kills even more organisms in the soil and waterways. In an ideal world we could just stop all use of these chemicals. But unfortunately the reality of such drastic measures would be reduced crop yields and mass starvation. So what is a caring farmer to do?
Nature provided an answer in a soil dwelling bacterium called Bacillus thuringiensis or Bt. These particular bacteria makes a series of proteins that are very toxic to the target insects but virtually harmless to all other life forms. Organic farmers have been safely using these live bacteria for over a hundred years. Agricultural scientists have been successful in transferring the gene for the insecticidal protein from the bacteria to plants. The resulting transgenic plants now protect themselves from insect pests without the need for continued organophosphate spraying.
Around the world these Bt crops have allowed farmers to reduce the amount of organophosphate insecticide sprayed by close to a hundred million pounds each year. Today only the target pest is killed in the fields containing Bt crops and all other insects are unaffected. This means that the insect biodiversity is not threatened in the same fields where crop yields remain high. Growing Bt potatoes resulted in dramatic reductions of insecticide use but, unfortunately, the main buyers of potatoes in North America (McCain Foods and McDonald’s) have stopped buying these environmentally friendly potatoes so the farmers have returned to growing traditional varieties and spraying them with traditional insecticides.
Corn and cotton are the two main Bt crops grown today but other Bt crops are working their way through the regulatory system and will further reduce our dependence on organophosphate insecticides in coming years. Healthier food is an added bonus of growing Bt crops. When insect pests damage an ear of corn the probability of fungal infection of the corn is enhanced. The fungi that grow on corn can produce nasty compounds (mycotoxins) that have been linked to animal and human birth defects. However, Bt corn has been demonstrated to have greatly reduced levels of these mycotoxins compared to conventional or organically grown corn.
Weeds are one of the largest problems for a farmer. Weeds drain nutrients and water from a field thereby reducing yields. The farmer can use mechanical or chemical means to reduce the weeds in the field. Mechanical weeding can have some significant negative consequences for soil structure, run-off and erosion. Therefore, a reduction in mechanical weeding would benefit the soil and the environment. Chemical herbicide use has been a major alternative to mechanical weeding, but it too can have some negative impacts on the environment.
Fortunately, not all herbicides are created equal. The newer herbicides have much lower environmental impact than those used just a few years ago. The replacement of older herbicides with the newer ones means far less impact on the soil micro-organisms and also cleaner water for frogs and fish.
Tolerance to the newer, less harmful herbicides has been engineered into some crops.
These herbicide tolerant (HT) crops allow the farmer to effectively control weeds while adopting reduced or no-till farming. The soil structure is enhanced, soil moisture and yields are maintained and topsoil loss is greatly reduced. In North America alone, over a billion tons of topsoil is saved each year by reduced tillage or no-till farming.
Approximately one third of all food rots before it can be eaten. Often this rot begins in the field long before the crop is harvested. Harsh chemicals are applied to crops and the soil to slow the rot caused by fungus. Even organic farmers use highly toxic copper compounds to slow fungal destruction of their crops. Research is well underway in developing fungal resistant crops that will not require toxic chemical sprays. Soon millions of pounds of toxic anti-fungal chemicals will no longer be applied to the environment because the plants will be engineered to protect themselves from fungal attack.
Just like people, plants suffer from viral infections. We have vaccines to help us fight off viral infections like the measles or the flu. But unlike us, a viral infection of a plant usually means death of the plant or severe reduction of yields. Researchers have been successful in "immunizing" certain plants against the viruses that attack them. The principle is similar. We are given a small amount of an inactivated virus to boost our immune system. The engineered virus resistant plants get a similar boost with one gene from the pathogenic virus. Usually it is the surface protein gene from the virus that is transferred into the plant. The result is a plant variety that is no longer susceptible to virus infection and damage. The papaya industry owes it continued existence in Hawaii to this technology. By engineering the surface protein gene from the Papaya Ringspot Virus (PRSV) into two varieties of papaya, there is now a healthy, growing industry when just 10 years ago the total destruction of the industry from the PRSV seemed inevitable. Ironically, these transgenic papayas are also being used to protect non-transgenic papaya plants. By encircling the non-transgenic papayas with transgenic plants the virus is blocked from reaching the susceptible plants. The PRSV virus has been found worldwide; consequently this particular product is of interest to papaya growing countries around the world.
These transgenic papayas have one added gene and are immune to the devastation of the PRSV virus. Now critics of food biotechnology are saying that these transgenic papayas have caused “genetic contamination” of their non-transgenic papayas. This is nonsense. The virus is already worldwide therefore so is the gene. If the critics like to call it “contamination” then this type of “contamination” with only the one gene separate from the pathogenic virus that is inserted into the papaya plant means the difference between a healthy field and crop verses a dead field and no crop.
A similar situation has occurred in Mexico. Again the critics claim “genetic contamination” of Mexican landraces of maize (corn) from Bt corn. So what is the result of the Bt gene introgression into the landraces of maize? More yield with less insecticide use and healthier food because of less fungal mycotoxins. Mexican maize farmers are very adept at maintaining a particular genetic makeup of their own landraces. It seems likely these added features from the addition of one gene may be of interest to them.
From coconuts to grapes, bacterial infections do tremendous damage to agriculture. Currently, the California grape/wine industry is facing a devastating bacterial assault. Pierce's Disease is a bacterial infection fatal to grape vines. A small insect called the glassy-winged sharpshooter spreads the bacteria. Currently, millions of dollars are being spent on insecticides to slow the northern march of this disease. Researchers have had some progress in engineering a different transgenic bacterium to counter the pathogenic bacterial infections of grape plants. It is ironic that at this time there are four counties in California voting on whether to ban the growing of all genetically engineered products. If this proposed ban is voted in by the people of the four counties there will be nothing to stop the devastation of the wine industry in those counties. Of course that will be after tons of insecticides will have been used to try to slow the disease.
The green revolution saw new breeding techniques, chemical fertilizers and irrigation to help keep food production ahead of population growth. Today, food production has fallen below the increasing demand of the human population. It is well recognized that traditional breeding has hit its maximum for yield increases. Therefore, unless we develop new ways to increase yields, there will be tremendous pressure to bring new land into production.
Although irrigation has greatly enhanced food production in many parts of the world it has also resulted in salt contamination of soils. Within the next thirty years it is estimated that one tenth of all arable land will be lost to salt contamination. Traditional breeding has few solutions for this but biotechnology has been very successful moving the genes that allow a mangrove to live in seawater, into crop plants. These salt tolerant plants will help keep the 750 million acres of salty soil in production.
A similar problem exists with aluminum. This common mineral threatens one third of all arable land. With no traditional breeding answers the best hope is the work of plant biotechnologists, which have shown excellent results in the lab. Hopefully aluminum tolerance will be a common engineered trait and, therefore, the one third of all arable land affected by aluminum will stay in production.
Water is essential for all life. Experts, including the UN-Food and Agriculture Organization, have made it clear that water resources will be critical in the coming century. Biotechnology is developing many different drought tolerant crops to maintain yields in water shortage conditions. Clearly, these will be of tremendous interest in drought prone areas of the world.
Each year Bt crops have allowed farmers to produce good yields without spraying hundreds of millions of pounds of insecticide. Herbicide tolerant crops maintain high yields with reduced tillage or no-till practices thereby saving huge amounts of topsoil and protecting waterways from run-off. Bacterial and viral resistant crops also maintain yield without the need for insecticide spraying. The future will see drought resistant, salt and aluminum tolerant and fungal resistant crops added to the varieties of biotechnology products that will help preserve arable farmland.
There are three certainties: the population will continue to rise for decades to come, people will be fed, and all agriculture has some impact. If we want to save biodiversity, we must save the remaining wilderness. Without a doubt the largest threat to biodiversity is converting wilderness to farmland. Agricultural biotechnology has shown that it can reduce the impact on the environment while maintaining or increasing yields. Therefore its incorporation into world agriculture will help protect biodiversity.
Malaspina University College
Originally published in The Globe and Mail Dec 1 2004