Table 4.1. Implications of Gene Technology for Biodiversity and the Environment 

Issue

Scientific convergence

Scientific divergence

Gaps in knowledge

Issue 1.  Direct effects Plants

Gene transfer

Does it happen?
Gene movement possible by pollen from open pollinated crops crossing with local landraces and/or related wild species, to form hybrids.

Crops vary in their extent of out-crossing. The presence of wild and/or weedy relatives depends on whether the crop is cultivated close to center of diversity. (CGIAR 2000b; EEA 2002)

Does it matter?
If crop/wild relative hybrids survive, reproduce and introgress genes back into native plant populations that then cause adverse environmental effects.

Uncertain if genes /traits moving from GM crops pose any new environmental risks or threats to biodiversity (eg maize in its center of diversity in Mexico) 

If hybrids survive, do introduced traits have any negative environmental consequences?  
Limited long term experimentation on this

Most research on gene flow in Europe. Little known about gene flow, and possible movement of traits from world’s major food crops to land races and wild relatives in their centers of diversity.

Low risk of domesticated crops becoming weeds themselves (based on history of safe use of crop plants).

Risk that GM crops/traits may escape from cultivated fields and if their traits are transferred into related wild species and form hybrids, these may survive to become weeds. Little evidence that this occurs in practice.

Specific trait effects on non-target species

Pesticidal plants (expressing toxins, such as Bt toxin) may affect related non-target species, as well as target pests.  

Need to compare genetic effects on non target species with present agricultural practices (eg pesticides, IPM, organic production).

Laboratory studies showed Bt corn may harm Monarch butterflies if pollen ingested at high dosage.  Subsequent field studies showed most presently cultivated strains of Bt corn pose little risk to Monarch butterflies in field. 
Plant Journal 2002; Pew 2002; Zangerl  2001; Shelton & Sears 2001.  

Difficult to extrapolate from laboratory studies to field. Need to develop better methods for field ecological studies, including base line data with which to compare new interventions.
Dale 2002; 

Extent of risk varies; need environmental impact assessment on case by case basis

Ecological monitoring desirable post release, to detect any unexpected events. (US NRC 2000; US NAS 2002)

Greater availability of monitoring data from presently cultivated GM crops (60m ha / 16 countries) would add to knowledge base (OECD 2001b)

Issue

Scientific convergence

Scientific divergence

Gaps in knowledge

Issue 2:  Indirect effects through changing agricultural practices

Pesticide use

Demonstrated reduction in pesticide use on GM crops with Bt genes (eg Bt cotton in USA, China, South Africa, Australia; Bt corn in USA). (CAST 2002, NCFAP 2002, ISAAA 2002a, Pray et al 2002 )

Herbicide use

Herbicide use changing , in volume and type (eg herbicide tolerant soybean)

Risk of developing herbicide tolerant weeds and/or excess herbicide use.

Herbicide tolerant crops encouraging low-till agriculture, with resulting benefits to soil conservation.

     Drought tolerance

     Salinity tolerance

Crops with industrial uses (eg plastics)

Experimentally possible, e.g. maize

Need to keep industrial crops out of the food chain.

Need regulatory framework