Posted on 20-6-2002

Ecological Risks Of GMOs High
From just-food.com Photo show Professor William Muir

Introducing genetically modified organisms (GMOs) into wild populations
holds a greater theoretical risk of extinction of natural species than
previously believed, according to two scientists from West Lafayette-based
Purdue University.

William Muir, professor of animal sciences, and Richard Howard, professor
of biology, used computer modelling and statistical analyses to examine the
hypothetical risks of introducing GMOs into wild populations. "We examined
these hypothetical situations because the range of new transgenic organisms
is almost unlimited," Muir said. "It is constructive for those developing
such organisms to be able to anticipate how they could pose a hazard." The
new computer models have shown that the risk of extinction is greater than
believed before, identifying three new scenarios in which GMOs could result
in the extinction of a natural population. "In the broadest sense, this
research tells one how to do risk assessment and what GMOs need further
containment," Muir said.

In 2000, Muir and Howard found that a release of fish that were larger, and
therefore had higher mating success, but also had shorter life expectancy,
could drive a wild population extinct in 40 generations. Muir and Howard
labelled this the "Trojan gene hypothesis." But further investigation has
found other scenarios that could lead to extinction.

In one scenario, a genetic modification increases the size of the male,
which results in the male finding more mates and also living longer. But if
the modification also has a third effect of making the male less fertile,
the predicted result is that the wild population will be extinct in just 20
generations. "We consider this an extreme risk," Howard said. "That's the
most severe time frame we've encountered so far." Howard said this risk
could arise if fertility was restricted in a GMO as a way to limit the
spread of the gene in the natural population. "This was the biggest
surprise for me, that if you lowered fertility of GMO the time course to
population extinction was faster rather than slower when the GM young have
better survival than wild-type individuals," he said. "I still look at the
graph of those data and find it amazing." The researchers also found
scenarios in which the introduced gene could spread through the population
but not reduce the overall population size. The researchers termed this an
invasion risk: "The invasion risk is an unknown in assessing the overall
risk," Howard said. "Given the biology, all we can say is that the gene
would increase in the population. We don't know if that would cause a
problem or not. In this case you wouldn't really know until you actually
released the gene into the population."

The results of the research were published in the most recent issue of the
scientific journal Transgene Research. The research was funded by the
USDA's Biotechnology Risk Assessment Programme. The Purdue research is part
of an ongoing effort by Purdue and the USDA to determine the risks of
biotechnology, particularly transferring genetic material from one species
to another, known as transgenic technology. "Consumer confidence in the use
of transgenic technology will only happen if there is a thorough, unbiased
examination of the risks," Muir said. The most recent study found that some
of the most significant risks occurred when the introduced gene increased
the viability of the adult organism, such as through improved immune
response or resistance to a disease or pathogen. "It's somewhat
counterintuitive that increasing the health of the adult could hurt the
overall population, but that is what we found if they had reduced
fertility," Howard said.

The scientists say the increased risk from transgenics comes about because
such transfers involve one gene from a different species. "This gene has a
mega effect that may confer new functionality on the organism," Howard
said. Traditional breeding, on the other hand, can only affect genes of
that species and involves an exchange of many genes, which the scientists
call polygenic inheritance. "Selective breeding is based upon polygenic
inheritance where the result is the cumulative effect of many of genes each
with a small effect. In contrast, most genetic modification involves one
gene with a major effect," Howard said. "The two methods are not
substantially equivalent, although they may be legally regulated as if they
are. "What this means is that the more wild an animal is, the greater the
environmental risk when using that animal to make a transgenic organism,"
Muir said. "In other words, a transgenic salmon is going to be more of a
risk to the environment than a transgenic cow."

Muir acknowledges that hypothetical experiments may not reflect what
happens in the real world, but he said the experiments err on the side of
caution: "If we show that these plants or animals may be a risk in a
laboratory experiment, it could be that they wouldn't be a risk in nature
because nature is less hospitable. It may be that things we find to be a
risk in the lab aren't a risk at all in nature. We feel that this is a
conservative approach to determining the risk." To get a more accurate
assessment of the risk of a GMO, a facility would need to be constructed
that would replicate the natural environment. Muir said some companies are
already considering constructing such testing facilities. "It's going to
cost millions of dollars to build elaborate testing facilities that are as
close to a natural setting as possible," he said. "But nobody said this is
going to be easy. What's at stake is important enough to spend that kind of
money."