ISIS Report 27/06/07
GM Contamination At 21 km and Farther
No Co-Existence Possible
Researchers find GM pollen cross-pollinated non-GM plants at 21 km and predict
much worse. Dr. Mae-Wan
Ho
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GM contamination rampant
Everyone knows by now that GM contamination of non-GM crops and produce
is inevitable. There have been142 contamination incidents recorded worldwide
since 1997, according to the GM Contamination Register [1]. This is an underestimate,
as not every shipment of non-GM produce has been tested, and not every incident
registered.
Many wary consumers are buying organic to avoid eating GM
food. But GM contamination of organic produce is no longer a rarity.
A recent case of serious
contamination involved a shipment of organic soybeans to a processor in the
United States. The processor had the shipment tested after being
tipped off by a buyer. The lab result showed up a massive GM contamination
of 20 percent. The organic certifier was unable to prosecute the supplier,
also in the US, who sent a different sample for testing. The processor lost
$100 000 in the incident, but the supplier was still selling his crop [2].
Perhaps in anticipation
of widespread contamination of organic produce, the European Union Council
of Agriculture Ministers voted in June 2007 that organic produce could contain
up to 0.9 percent GM [3], despite the fact that, in March the same year, the
European Parliament passed a directive setting the contamination threshold
at 0.1 percent, which effectively maintained the organic industry’s insistence
on “zero tolerance” of GM contamination.
Current
separation distances derisory
The current regulatory regime where GM and non-GM crops are allowed to
grow in adjacent fields separated by tens or hundreds of metres is based on
the assumption that the separation distances are sufficient to reduce cross-pollination
levels to the acceptable minimum.
Pollen flow is not the only
means of GM contamination. Other means involve GM seeds: impurities in the
seed stock, volunteers from a previous crop, seeds dropped during transport,
seeds inadvertently mixed by suppliers and during processing. Seeds persist
much longer and can travel much farther. When the same machinery is used in
several fields for harvesting, cultivation and spraying, seeds will be readily
moved around from one field to another.
But even the extent of cross-pollination
is greatly underestimated, as has been pointed out, pollen can remain airborne
for hours and a 25 miles-per-hour wind speed is not unusual [4], which is
why extensive contamination of certified seed stocks had been detected as
far back as 2003 (Transgenic Contamination
of Certified Seed Stocks, SiS
19).
Two recent scientific studies
have now confirmed that the extent of cross-pollination has been greatly underestimated.
GM bentgrass pollen spreads 21 km or more
A research team led by scientists
at the US Environment Protection Agency in Corvallis, Oregon,
used an atmospheric model of wind blowing above fields planted with GM bentgrass
to look at GM pollen dispersal, combining modelling with actual analysis of
cross pollination with non-GM plants of the same or related species [4]. The
GM bentgrass carried the glyphosate tolerance trait, which provided a ready
selectable marker for cross-pollination.
During extensive greenhouse and laboratory testing, glyphosate-tolerant
progeny of non-GM test plants were found up to 21 km from the GM fields.
This was consistent with the model of wind direction and speed, which
showed movement of pollen up to 15 km from the GM fields by the first hour;
and maximum travel distances increased to 40 and 50 km after two and three
hours respectively. The three-hour cut off period was based on previous findings
that the viability of the grass pollen dropped to zero within three hours.
These findings were at odds with previous small-scale experiments,
involving hundreds of GM plants in small plots, which showed pollen dispersal
limited to a few kilometres, basically because the source of GM pollen was
too small. It is like putting a drop of ink in an ocean, which soon gets diluted.
In the present experiment,
GM bent grass was planted in 162 hectares, at about 2.8 million seeds per
hectare. This provided realistically high pollen concentration for the estimation
of pollen dispersal. The maximum potential spread of 21 km observed was an
underestimate because pollen trapping plants were not set much further than
the distance observed. According to the model, GM contamination could be as
far as 75 km downwind of the GM field.
Realistic modelling shows highly variable and unpredictable
GM pollen spread, but most studies underestimate the real extent
In a similar theoretical study, researchers at Exeter University
in the United Kingdom used records of wind direction and speed from 27 weather
stations across Europe to predict pollen dispersal and wind-borne cross-pollination
in maize, oilseed rape, sugar beet and rice [5]. Their results showed that
cross pollination rates vary greatly according to the relative orientation
of the GM and non-GM fields, and substantially from year to year. The main
determining factor is wind direction, which accounts for most of the variation,
75 percent in the case of maize in the UK.
For maize and rice, cross-pollination rates are relatively
high only if the non-GM field is downwind of the GM field with respect to
the prevailing winds over the short pollination period. In contrast, contamination
rates vary least with field orientation in crops with relatively long flowering
periods, such as oilseed rape and sugar beet, because the distribution of
wind directions becomes more even as the flowering period lengthens.
“Consequently, even replicated
field trials may inaccurately estimate typical levels of cross-pollination,
and therefore distort our perception of the separation distances required
to achieve sub-threshold adventitious GM presence.”
The best one could do is
to predict the likely range in levels of cross-pollination based on limited
data typically available from field trials, and to introduce time delays between
the peak-flowering periods in adjacent fields to reduce cross-pollination
to a specific level.
What the model actually
says is that a contamination rate measured in any single experiment without
knowing the prevailing winds is unreliable, because the wind changes direction
from day to day and year to year. The model gives the mean maximum and minimum
relative rates based on prevailing conditions, not the absolute rates. For
example, suppose that a rate of 0.001 percent contamination was measured in
a single field trial and the necessary meteorological records were not available.
For the UK, the mean maximum and minimum relative cross-pollination rates
for maize were estimated by the model to be 7 and 0.0005 respectively, in
the case of maize grown in fields of dimension 500 x 200m, separated by 1
000 m. The maximum possible rate is given by the ratio of the maximum and
minimum rates multiplied by the measures rate, i.e., 7/0.0005 x 0.001 = 14
percent, which is quite substantial. If the prevailing weather and wind conditions
were known, then the estimate improves considerably. Suppose that the maize
trial was carried out in Leeds in 1998, and the relative orientation of the
GM and non-GM fields was 100o, and according to the prevailing
wind conditions, the minimum relative rate was 0.5 while the maximum relative
rate was 9.5, then a measured value of 0.001 percent would give a maximum
possible rate of 9.5/0.5 x 0.001 = 0.019 percent, substantially less than
the previous estimate. The moral in the example is that wind speed and direction
should be measured during future field trials. No such data currently exist.
The researchers stress that their analysis is conservative,
because if a very large quantity of pollen is released in strong gusts of
wind, then cross-pollination rates will be even more extreme.
For oilseed rape, sugar
beet and rice, contamination rates could be reduced by 50 percent when the
lag between the times of peak flowering of the GM and non-GM fields is 13
days and by 90 percent when the lag is 24 days. For maize, similar reductions
require lags of only 4 and 8 days respectively because of the shorter flowering
period.
Maize, sugar beet and rice are almost entirely cross-pollinated
by wind, whereas oilseed rape is cross-pollinated by both wind and insects.
Stop
planting GM crops right now
It is clear that transgene contamination is inevitable and unavoidable
if GM crops are planted. We must make the choice to stop planting GM crops
right now, not only to avoid the massive economic losses involved in transgene
contamination incidents, but also on the basis of the now irrefutable evidence
that GM crops are neither safe not sustainable [6, 7] (Scientists for a GM Free Europe,
No to GMOs, No To GM Science)
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