The Genetics Controversy - Agri-culture: Reconnecting People, Land and Nature - page 133

risk and two risks for human health. The degree to which each of these
poses an actual risk is a combination of both a hazard and exposure, since
not all hazards constitute a risk in practice. Thus, the risks and potential
benefits are different for every application of genetic modification. Each
class of risk is analysed below in light of recent independent scientific
knowledge, drawing particularly upon analyses from the field. 7
Gene flow
The first potential environmental risk is gene flow, where transgenes could
transfer from a genetically modified organism to wild relatives and/or
bacteria in soil or human guts. Gene flow is a natural phenomenon, with
many species of plants crossing with related species. As a result, the
question of novel risk rests on whether the transgenes could lead to the
transfer of undesirable traits, and the emergence of permanently trans-
formed populations. As these transfers have not occurred in nature, it is
impossible to predict the effects with confidence. 8 The main concerns lie
in pollen transfer. However, it is important to note that pollination is not
the same as gene flow; although pollen can travel many kilometres, only
rarely will it result in a fertilization event. 9 Furthermore, many genetically
modified lines are male sterile; so, even though pollen transfer may occur,
pollination cannot. A further concern is the potential for uptake of
transgenic DNA by soil bacteria, which is referred to as horizontal gene
flow. 10 The important question is not so much whether gene flow occurs;
rather, to what extent might transgenes affect native plant ecology? As
Brian Johnson of English Nature put it: 'To add genes from other plants
unwittingly and randomly to native gene pools may result in phenotypic effects which could
change the way entire genomes relate to their physical and biotic environments.' 11 Thus,
the transfer of transgenes that are designed to prevent germination would
lower fitness of new crop-native hybrids, whereas resistance to insects,
fungi and viruses could substantially increase fitness. This could lead to
the emergence of weeds with multiply stacked genes for herbicide
tolerance.
Emergence of new forms of resistance and secondary
pest and weed problems
The second environmental risk centres on the potential for the emergence
of new forms of resistance and/or secondary pests and weeds. Resistance
had already emerged on a very large scale in modern agriculture before