Hope Not Hype - Third World Network

146 Hope Not Hype
The predominant trait in GM crops is herbicide tolerance (HT) for the purposes of
consolidating weed control under a single or small number of proprietary agrochemicals.
Introducing HT traits into crops also creates the risk of HT weeds through gene flow
(Heinemann, 2007; Zapiola et al., 2008). For example, a weed may arise from the transfer
of the gene that confers herbicide tolerance to a non-crop plant, or the flow of crop seeds
to land being used to cultivate other kinds of crops. Wherever the associated herbicide is
being used, the undesired plant will prosper. The speed of spread of HT canola attests to
this (Marvier and Van Acker, 2005). Sometimes weeds created by transgene flow persist
even outside of the normal usage of the herbicide. This case is dramatically demonstrated
by the development of glyphosate-resistant creeping bentgrass (GRCB) in the United
States following a brief field trial.
Our results document not only the movement of the glyphosate resistance transgene from
the fields, but also the establishment and persistence of high frequencies of GR plants in the
area, confirming that it was unrealistic to think that containment or eradication of GRCB
[Agrostis stolonifera L.] could be accomplished (Zapiola et al., 2008, p. 486).
The presence of transgenes can affect market certifications and introduce the risk of
litigation against farmers found to possess the transgene without permission, even if the
gene is not in the farmer’s intended crop. The impacts on the agroecosystem can also be
long-lived.
This finding of [HT oilseed rape] volunteers, despite labour intensive control for 10 years,
supports previous suggestions that volunteer OSR [oilseed rape] needs to be carefully managed
in order for non-GM crops to be planted after GM crops (D’Hertefeldt et al., 2008, p. 316).
Special risks from complex traits
Since GM traits are usually created in continuous arrays of transgenes, the effect of
gene flow from GM crops to other plants can be more severe than general gene flow for
traits that are based on multiple genes (Heinemann, 2008). This is because it is less likely
that all necessary genes will be transferred by breeding when they are distributed between
different chromosomes.
The recent rush to produce greater tolerances to stresses, such as drought, salt and
temperature, in crops through genetic engineering creates additional risks for weed
generation (Pennisi, 2008).
Organisms that greatly overcame [currently limiting physiological or morphological
constraints], perhaps through gene transfers, would be supercompetitive species that could
potentially invade into and change the structure of nonagricultural ecosystems (Tilman, 1999,
p. 5997).
Since the stress tolerance traits would arise from transgenes, their close linkage and
perhaps multiple copies would create a quantitatively higher risk over the normal problems