It is hard to deny that emphasis on large scale monoculture mode of agriculture has had a negative impact on agricultural biodiversity. Intensive agriculture of the recent decades has resulted in a dramatic decrease in field fauna and flora. Adapted local varieties have gotten eliminated as a result of the high performance cultivars and many variants of crops have gotten irretrievably lost as a consequence of the implementation of monocultures. . It is claimed that 75% of plant genetic diversity has been lost since 1900 as farmers turned to genetically uniform mass produced varieties. It is assumed that introduction of GM crops would result in genetically uniform varieties; this would slowly degrade the agro-biodiversity and eventually, the environment. Another major concern associated with the Genetically Engineered (GE) crops is the spread of introduced genes by gene flow to nearby crops or wild plant populations, especially through the pollen grains. Another hazard is the effect of toxins like cry proteins from Bt crops on non target invertebrates leading to the disruption of the natural populations of these invertebrates causing possible harm to the ecological balance. These are the arguments that are put up as the impacts of GM crops on agricultural diversity.
The adoption of herbicide resistant crops is associated with conserved tillage practices, reducing run off and erosion and enhancing the water infiltration into the soil. Hundreds of independent studies made in independent lab based (9 Bt crops in 17 countries) and field based (5 Bt crops in 13 countries) studies have concluded that the non target effects of broad spectrum insecticides is much worse than that of the Genetically modified Bt crops. Lab studies identified greater levels of hazard than field studies and this is partially explained by frequent higher exposure of organisms to the transgenic proteins in labs compared to the organisms raised in the field. The U.S. National Research Council had released a comprehensive assessment of the effect of GE crop adoption on farm sustainability in the U.S. that concluded, "generally, [GE] crops have had fewer adverse effects on the environment than non-[GE] crops produced conventionally". Genetic containment of transgenic crops through development of methods to prevent the spread of introduced gene is of primary concern. Such gene flow barriers may be physical like the use of isolation zones and barrier crops or biological like male sterile plants and chloroplast targeted transformation. Plastid targeted transformation technology can significantly reduce gene flow since pollens, a major source a gene flow do not contain chloroplasts i.e. chloroplasts are maternally inherited in higher plants. So the transgene introgressed into the chloroplast genome is not transferred through the pollen of the GM plant.
The population of the world has exploded from two billion at the start of the twentieth century to about 7.2 billion today. Methods followed in the previous century cannot be replicated for feeding the current population. Hence the need has arisen to prioritize between food security for feeding the rising population and adoption of the less intensive traditional agriculture practices. The variants the farmers developed were adapted to the locality and are infact valuable genetic resources. It is our ignorance that resulted in a part of this resource getting lost. But now this mistake is realized and maintenance of plant genetic resources is of prime importance and efforts are being taken from all fronts to collect, store and characterize the traditional varieties. Studies are being made to evaluate their possible use in crop improvement through genetic engineering as well. So, GM technology has infact bolstered the search for novel genes in underutilized alternative crops that may be used for enhancing crop quality. Thereby increasing the efforts to conserve and characterize agro-biodiversity.
1. Carpenter J. Impacts of GM crops on biodiversity. GM Crops 2:1-17 (2011).
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Post Graduate fellow pursuing Master of Science (Ag) in Molecular Biology and Biotechnology