Fwd: Dutch Precaution Keeps Bt Crops At Bay

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Fri, 10 Oct 2003 19:59:49 +0100

 

Dutch Precaution Keeps Bt Crops At Bay

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The Institute of Science in Society

Science Society Sustainability

http://www.i-sis.org.uk

 

General Enquiries sam

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ISIS Director m.w.ho

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Dutch Precaution Keeps Bt Crops At Bay

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Dutch ecologists outline risk-assessment strategy for Bt-crops based on the

precautionary principle, highlighting special concerns associated with small

farms in Europe as opposed to much larger farms in the United States. Dr.

Mae-Wan Ho and Prof. Joe Cummins report.

 

The complete document with references

(http://www.i-sis.org.uk/full/DPKBTCABFull.php), is available in the ISIS

members site. Full details here (http://www.i-sis.org.uk/membership.php)

 

The Dutch take the precautionary principle very seriously. In the matter of

approving GM crops, " the mere conception of a possible ecological hazard, even

in the absence of scientific evidence, requires precautionary interim measures

until research enables full risk management. " That’s the position stated by Bart

Knols and Marcel Dicke, entomologists from Wageningen University in the

Netherlands, in their correspondence to Nature Biotechnology in September 2003

[1], and they may be right.

 

Over the past eight years, the Dutch Parliament has mostly prevented cultivation

of GM crops on Dutch soil, and it remains to be seen whether the new government

will stick to this policy.

 

The Committee on Genetic Modification (Cogem) is responsible for regulating GM

crops in the Netherlands. A recent Cogem-sponsored survey of nine prominent.

Dutch ecologists indicated that, in line with adherence to the precautionary

principle, answers to ecological issues too important to be ignored are still

lacking. These include outcrossing of transgenes to related plant species,

effects on soil ecosystems and, in particular, impacts on multiple layers of the

food web.

 

The plants as primary producers are eaten by primary consumers or herbivores,

which are in turn consumed by and secondary consumers, or carnivores. These

feeding relationships form an intricate web of inter- and intraspecific

interactions. Incorporating Bt transgenes in a plant genome results in

production of delta-endotoxins, thereby reducing feeding by herbivores. But

effects on other levels remain largely unknown.

 

Knols and Dicke point out that accumulation of toxins in non-target herbivores

may affect natural enemies, yielding secondary pests that may require

chemical-based interventions to reduce crop losses. Persistence of toxins in the

soil may affect soil arthropods, and disturbance of below-ground interactions

may in turn impact on the above-ground food web.

 

Furthermore, how a plant allocates resources towards producing toxin affects its

metabolism, and that may impact on herbivores and carnivores. These higher level

disturbances may favour evolution of Bt resistance in pests.

 

Farming in the Netherlands is predominantly small-scale. And that raises

additional concerns, as the interaction between Bt crops and surrounding natural

or semi-natural ecosystems will be orders of magnitude greater than in countries

with large-scale Bt-crop cultivation like the United States. For example, even

though the Monarch butterfly may only be harmed by high-expressing genotypes in

laboratory experiments, Bt pollen may have much larger impacts on vulnerable

and/or endangered Dutch lepidopteran species, several of which are already on

the verge of extinction and survive only in isolated refuge areas.

 

The presence and persistence of Bt toxins in soil and resulting effects on the

below-ground ecosystem may actually affect the succession of plant species and

thus result in changes in floral composition in the natural vegetation. Finally,

cultivating crops expressing different Bt toxins in adjacent areas may enhance

development of cross-resistance, a risk that, again, should be considered

relatively high in the Dutch landscape with small-scale crop production.

 

These considerations have prompted the researchers to define a four-pronged

approach in risk assessment of Bt crops:

 

Identifying the key species participating in food web interactions, and

elucidating their ecological function(s).

Exposing these key species to Bt toxins, and monitoring the effects on both

below- and above-ground trophic levels.

Identifying effects of Bt plants at the community level, which require

population studies and analysis of interactions with adjacent ecosystems.

Developing models to describe these processes ranging from organism to

population level, to provide insights into potential ecological effects over

larger temporal and spatial scales.

These goals are ambitious and will require lengthy and costly studies. Dutch

environmental policy advocates crop intensification through environmentally

sound means, including nonchemical pest control strategies.

 

" Whether or not Dutch postcards will ever feature windmills surrounded by fields

of bright yellow transgenic oilseed rape remains to be seen, " the authors wrote,

" but that it will take a long time is certain. "

 

There can be no greater contrast between the Dutch approach to risk assessment

and that of the United States. In the United States, GM crops with pesticidal

genes are regulated by the Environmental Protection Agency (EPA) under the

Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA). The actual

evaluations are done by Scientific Advisory Panels (SAPs) chosen from academia,

corporations and bureaucratic scientific professionals. The evaluation of Bt

crops is published as Biopesticide Registration Documents [2-9].

 

The underlying principle of the SAPs appears to be that the Bt crops should be

considered safe until proven otherwise. Furthermore, the SAPs consider each form

of the Bt toxin (for example Cry1Ab, Cry1Ac, Cry1F , etc.) as an independent and

separate pesticide from the other forms. But the actual transgenes for a single

toxin, say, for example, Cry1Ab, may differ from one crop to another. Some are

completely synthetic, with regulatory inserts and radically altered DNA codes,

and the final product, the protein toxin, may be considerably shorter than the

original native toxin. Nevertheless, these are not considered separately. The

SAP process, with its insistence on evidence of harm for each and every variant

of the toxin genes seem to assume that fundamental differences in the transgenes

of a particular toxin are insignificant even though they are bound to greatly

influence activity of production of a toxin, as well as the stability and

motility of the genes.

 

Some of the EPA assessments appear to depend on selection of evidence rather

than full and truthful reporting of all evidence. For example, the SAPs proclaim

that " there is no significant risk of gene capture and expression of any Bt

endotoxin by wild or weed relatives of corn, cotton or potato " [4,5].

 

The resistance management strategy approved by EPA allows the use of pesticide

spray in the refuge as well as on the transgenic crop. It assumes that

resistance appearing in a particular transgenic crop will not affect another

that produces a different Bt toxin, and finally, a resistant mutant in the

target pest is necessary, but not sufficient to trigger regulatory action; only

in the case of a substantial outbreak is regulatory action required [6].

 

The benefit assessment by SAPs predicted a reduction in chemical pesticides with

the use of Bt crops, but noted " environmental benefits were difficult to

quantify " .

 

The Dutch approach to Bt risk assessment is based on the precautionary principle

and thorough scientific investigation prior to widespread release of transgenic

crops. In contrast, the US EPA use SAPs to approve widespread release of

transgenic crops presuming they are safe, and dismiss contrary evidence that

comes to light.

 

 

 

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http://www.i-sis.org.uk/DPKBTCAB.php

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General Enquiries sam

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