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."
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