Contents - Faperta

434 Biotechnological Approaches for Pest Management and Ecological Sustainability
maturity (Parker and Kareiva, 1996). Transfer of a gene conferring a particular character,
whether through genetic modifi cation or traditional breeding, may have a positive infl uence
on one component of the overall demographic processes under some environmental
conditions, and a negative infl uence under other conditions, for example, genetically modifi
ed seeds of oilseed rape with modifi ed oil content (high- stearate) can have enhanced
longevity in soil (Linder, 1998), but the high-stearate gene confers reduced vigor on seedlings
(Linder and Schmitt, 1995). Therefore, changes in a single demographic process may
not be a good measure of plant invasion, a methodological concern often overlooked when
enhanced invasiveness of genetically modifi ed crops is considered.
When assessing the invasiveness potential of genetically modifi ed crops, the key issue to
address is whether their weedy characteristics are likely to be different when the expression
of the transgene is taken into account. In this context, the transgene-centered approach
to biosafety is important (Metz and Nap, 1997). Experimental studies investigating
invasiveness need to be established in appropriate and well- defi ned environments, and
measure parameters that encompass all demographic processes. The demographic parameters
of genetically modifi ed oilseed rape with resistance to the herbicide glufosinate and
conventional oilseed rape have been estimated over a three-year period involving a range
of climatic conditions (Crawley et al., 1993). There was no evidence to indicate that genetically
modifi ed oilseed rape may become invasive in undisturbed natural habitats.
The genetically modifi ed lines tended to be less invasive and less persistent than the
nongenetically modifi ed counterparts. However, a few studies have also indicated that
herbicide-resistant oilseed rape, sugarbeet, and maize, and Bt and pea lectin transgenic
potato were found to be no more invasive, or more persistent than their conventional counterparts
(Crawley et al., 2001).
Assessment of Nature of Risk to the Environment
Risk Assessment
“Risk” means many different things to different people. It depends on social, cultural, and
economic background and value system (Kaplan and Garrick, 1981). A common description
of risk is “probability of harm.” When taking the magnitude of the potential harm into
account, risk is expressed as:
Risk Probability Consequence Likelihood of event Negative impact of
the event.
Probability of Harm
The negative or undesirable impact of an event is commonly referred to as hazard
(Wachbroit, 1991). Managing probability, or consequence, or both infl uence risk. Risk is
determined by the following questions. What can go wrong (possibility of harm)? How
likely is that to happen (probability of that harm occurring), and what are the consequences
if it happens (consequence of harm)? The concept of risk is therefore taken as the possibility
of harm that may occur, rather than the probability of harm. It may be wrong to assume that
any effect automatically results in an undesired negative impact. If the probability of a