Indirect effects of GM plants on the enviroment

The use of conventional agricultural pesticides and herbicides has damaged habitats for farmland birds,wild plants and insects and has seriously reduced their numbers.GM crops may have indirect environmental effects as a result of changes in agricultural or environmental practices associated with the new varieties.


Farmer spraying pesticide.

It remains controversial whether the net effect of these changes will be positive or negative for the enviroment,so more comparative analysis of new technologies and current farming practices is still required.

Using GM crops which are insect resistant because they carry the Bt gene has reduced insecticide use on maize,cotton and soybean.The environmental benefits include,less contamination of water supplies and less damage to non-target insects.This in turn may be beneficial to biodiversity,in comparison to conventional crops that receive regular pesticide applications.Also health benefits to farm workers due to reduced chemical pesticide spraying have been documented in China.

Scientists agree that herbicides-tolerant crops are encouraging low-till agriculture(which limits the use of plows),thus helping in soil conservation.On the other hand,greater use of herbicides could further erode habitats for farmland birds and other species.

Extensive farm-scale evaluations of the impacts of GM herbicide-resistant crops in UK concluded that commercialization of these crops would have a range of impacts on weed vegetation,with consequent effects on herbivores,pollinators and other populations that feed on it.These observations varied for different GM species with negative effects in sugar beets,positive for maize and no effect for oilseed rape.

The use of herbicides and insect resistant crops could result in the emergence of resistant weeds and insects .This has often occurred as a consequence of conventional herbicide and insecticide spraying.Several weed species have developed resistance to specific herbicides which are extensively used in combination with herbicide-resistant genetically modified crops.Insect resistant Bt-crops similarly could lead to the emergence of Bt-resistant insects.The extent and severity of impacts of resistant weeds and insects are subject to debate(GM Science Review Panel)

New GM crops are being developed that can withstand environmental stresses such as drought,salinity or presence of aluminum in the enviroment.They may allow cultivation of soils that are presently of low productivity for agriculture.Scientists agree that these crops may be environmentally beneficial or harmful depending on the particular crop,trait and enviroment(ICSU).

The scientific community recommends more research and better monitoring regarding post-release effects of genetically modified crops(ICSU,FAO,2004).