Globally, some 145 million acres of transgenic crops were planted in 2002, a rise of 12% from the previous year. Adoption of food biotechnology crops is growing. Recently a great deal has been said about genetically modified food. The debate (or the lack thereof) has been raging in Europe for years. Now the issue has arisen in North America. Although much has been said on the subject, the public has been generally ill informed. Half-truths and misinformation have been the hallmark of many critics of food biotechnology, while secrecy has been the norm for the industry. Neither of these positions has helped the public take part in a meaningful debate. As long as there is a lack of accurate information, suspicions and fear can influence policies. Over 95% of transgenic crops grown are either herbicide tolerant or insect resistant. This article will look at the insect resistance trait engineered into food crops.
Organic farmers have used the soil bacterium Bacillus thuringiensis (or Bt) as a natural insecticide for forty years. The bacteria produce a group of proteins that are toxic to specific insects. These proteins have no effect on other animals. Scientists were able to transfer the first Bt protein gene from the bacterium Bacillus thuringiensis (Bt) into a plant in the late 1980's. Several more years of research followed, which examined many aspects of the transgenic Bt crop. In 1995 the first commercial transgenic Bt crops were planted. Since 1995 there has been an increase each year in the number of acres planted with Bt crops. Bt crops include corn, cotton and potato. These Bt crops produce the Bt protein (at levels equal to organic bacterial sprays) and therefore protect themselves from insect pests. This self-protection has several advantages. Most Bt engineered crops require far less insecticide spraying, while in others there is a dramatic reduction of toxic fungal growth in the crop.
Cotton is one of the most heavily sprayed crops in the world. In the US, cotton crop spraying accounts for approximately two thirds of all organophosphate insecticides used. According to the Environmental Protection Agency (EPA), the use of Bt cotton varieties has resulted in a 66% reduction in insecticides most toxic to birds and fish and a 33% reduction in insecticides most toxic to humans. This amounts to several million kilograms less insecticide being sprayed on fields each year. Presently, the control of the corn rootworm requires several applications of organophosphate insecticides each year. A new variety is set to come on the market that will dramatically reduce organophosphate insecticide use. This new variety of Bt corn specifically targets the rootworm, thereby reduces or eliminates the need for insecticide applications. Growing most other varieties of Bt corn do not generally decrease insecticide use, as the insect pests that attack the corncob are not well controlled by spraying. The benefit of these varieties comes in the form of healthier food. When an insect damages the corncob the result is growth of a variety of fungi. These fungi can produce mycotoxins, some of the most toxic compounds on the planet. Bt corn varieties have shown greater than 90% reduction in mycotoxins when compared to non-Bt corn varieties.
Opponents to food biotechnology continue to say Bt corn kills monarch butterflies.
This myth comes from one report done in the laboratory in which monarch butterfly caterpillars were fed large amounts of Bt corn pollen (thousands of times that found in a corn field). The result was the death of some caterpillars. This was not surprising to scientists, as the Bt protein that was engineered into the corn was designed to kill caterpillar pests of corn. However the result of this research should not be directly applied to the field. The researcher himself stated " it would be inappropriate to draw any conclusions about the risks to monarchs in the field based solely on this study". To the contrary, over thirty field studies have shown monarch butterflies are not threatened by Bt corn pollen. The EPA has stated that there is minimal risk to monarch butterflies from Bt corn pollen. According to Monarch Watch, the population of monarch butterflies has increased dramatically since planting of Bt corn began. Last year had a record return of monarch butterflies to their winter range (3-6X average return). In fact, the biggest risk to monarch butterflies is habitat destruction in their wintering grounds of Southern California and Mexico.
Impact on other non-target species is a related concern of critics. Extensive environmental impact assessments are done prior to commercial release of all transgenic crops. Scientists have been unable to find a toxic level for Bt proteins in non-target test animals. Studies have looked at effects of the Bt proteins on catfish, aquatic invertebrates, earthworms, springtails, green lacewing, ladybird beetle, honey bees (adults and larva), parasitic wasps, quail and other species likely to come in contact with the crop. In every one of these studies the result was "No adverse effects were observed". Further studies looked at how diets of Bt corn might affect animals that feed on the transgenic corn. When nearly 5 grams (about a sugar cube) of pure Bt protein toxin was fed to test animals there was no effect on mortality. Amounts of Bt protein in corn kernels are approximately one million times lower than those fed to test animals. In all non-target species, the Bt protein is digested along with every other protein consumed. Persistence of the Bt proteins in soils after crop harvests continues to be investigated. Under most field conditions the protein rapidly degrades. Those few conditions where the protein persists are the subject of further research. Organic farmers have been using the Bt bacterial insecticide for over forty years. Studies have shown the levels of Bt proteins found in the soil of organic farms are similar to the levels found in soil of fields planted with Bt crop varieties. There have been no adverse effects on soil ecology reported in over forty years of organic use of Bt bacteria. There is no scientific reason to expect anything different for biotechnology developed Bt crops.
Compare these results to those that look at the environmental impact of organophosphate insecticides used to control insect pests. Organophosphate insecticides kill virtually every insect on contact. Bt crops only kill the target pests. Bt crops have been proven to dramatically reduce the use of organophosphate insecticides and should be applauded by everyone interested in protecting the environment. Less spraying of crops also means there is significant reduction in fuel consumption by farm machinery. This helps Canada in its goal of reducing greenhouse gas emissions. There has been much written about food biotechnology. Unfortunately, a significant amount of it is not true. If the public is to have a real debate on this issue, then accurate information must be the starting point.
Robert Wager
Malaspina University College
Originally published in the Globe and Mail, Feb 14 2003