GM technology: As risky as life itself

By Alex Kirby BBC News Online environment correspondent

Remember the monarch butterfly? You will if you worry about genetically modified (GM) crops.

Monarch butterfly: Protesters' icon

In 1999, US scientists said GM pollen was fatal to monarch caterpillars.

It can be - but the story is a little more complex than that.

And so the monarch has become a telling symbol of the need to think through our fears of GM technology before we condemn it altogether.

Having thought them through, we may still decide against it, judging it an answer looking for a non-existent problem - and a risky answer at that.

But those who say it deserves a hearing do themselves deserve a hearing, at least.

Lethal dose?

The 1999 researchers fed monarch caterpillars in a laboratory on their normal diet, milkweed, after dusting the leaves with pollen from GM corn (maize).

GM pollen killed the lab caterpillars

They found that 44% of the caterpillars died after four days, while none of a control group exposed to conventional corn pollen did so. The following year another group of researchers announced similar findings.

In contrast, a third group was unable to establish any link between GM pollen and harmful effects in another butterfly, the swallowtail.

It was not until 2002 that the US Agricultural Research Service (ARS) felt able to declare that the pollen posed no "immediate significant risk" to the monarch.

Was the original research therefore wrong? No. But it had been a laboratory study, unable to establish what might happen in the real world.

The ARS study was able to look at several additional factors affecting the caterpillars' GM pollen intake in the field:

• how much they needed to eat to kill them
• how likely they were to be exposed to a lethal quantity
• whether the GM pollen harmed them more than the chemical pesticides normally used.

Asking questions like those, and answering them, does not give GMs an automatic green light.

Into the unknown

We need to ask many more: are swallowtails naturally resistant to something that fells monarchs, for instance?

Do monarchs face so many other perils that they should be protected from the added risks of GM pollen?

Might there be long-term, perhaps sub-lethal effects, detectable only after the butterflies emerged from the chrysalis?

Are some species especially susceptible to GM attack at particular stages of their development?

We do not yet know whether monarchs or any other species exposed to pollen (or other GM byproducts) may be at risk.

Conventional penalty

All we can do, the technology's proponents argue, is continue to monitor what is happening in the field as well as in the lab - and remember the effects on wildlife of our present chemical-based agriculture.

How a plant is genetically modified

In pictures

And with every new technology, they say, there are risks to weigh against benefits. GMs, on this argument, are not intrinsically different.

It comes down to the old argument about horses for courses - judging each proposed application of the technology case by case.

What concerns many opponents of GM crops is the impossibility of turning the clock back if they do finally prove dangerous, whether to other species or to human health, or by creating hybrid plants.

If they do harm us, or wildlife, or if they contaminate conventional or organic crops, there will be no hope of recalling them.

Moving on

The case-by-case approach applies here, suggesting GMs should be grown only where they remain behind an effective cordon sanitaire protecting other crops, and labelled so anyone who eats them does so knowingly.

Farming does not stand still: science keeps opening new doors, which means farmers have to develop new ways of managing their crops and the fields where they grow.

The supporters of GMs say both the risks and the benefits hinge on the genes you engineer into an alien species, and on how you then take care of the result.

What any crop does to the environment depends on how you manage it, and GMs are at least worth trying, they argue.