ISIS Report 19/09/11
Glyphosate and Monarch Butterfly Decline
Glyphosate destruction of monarch butterfly breeding
grounds suspected Dr Eva
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butterfly migration abundance has been declining over the last 17 years; a new study finds . Extreme weather conditions, over-logging of their migratory destination in Mexico and the herbicidal destruction of their breeding grounds in the US are to blame.
Monarch butterflies (Danaus plexippus),
also known as milkweed butterflies, are famous for their spectacular migration
from North America to Mexico over the wintering months. The adults live for
only 4-5 weeks, but another wonder of these butterflies is that one special
generation born in the autumn lives for 7-8 months enabling them to make this
astonishing journey that can be as long as 2 800 miles.
Millions descend on central Mexican forests every
year to escape the harsh winters of North America. They hibernate until the
warmth of spring brings them back to life, when they make the journey back to
their breeding habitat on milkweed plants in North America. No individual makes
the whole return journey, but instead the short-lived offspring lay eggs along
the way, until their descendents make it back home.
This spectacular phenomenon is now showing
significant signs of decline in a study led by Isabel Ramirez at Universidad Nacional
Autonoma. They analysed data of the total area occupied by the butterflies in
hibernation over the last 17 years (published online by World Wildlife
Fund-Mexico since 1994) using two different statistical methods, and both showed
significant decreases. These are standard regression analyses for determining
the correlation between two variables, in this case colony area and time. The
linear model assumes simple linear relationships between the two, while the
exponential model assumes exponential decreases in area over time (as
populations tend to grow or decrease exponentially, this is a common method for
analysing population numbers). Although the numbers vary from year to year, the
highest area reported was in 1997, where they occupied 20.97 hectares. In 2010,
the lowest area was recorded, at just 1.92 hectares. The 2010-11 season has
shown a slight increase to 4.02 ha. The results are presented in Figure 1.
Figure 1 Decline
of monarch butterfly over time. Bars represent the total size of colonies over 17
seasons from 1994-5 to 2010-11. The dashed line
shows the average colony size over this period of 7.24 hectares. The lines show
the total area calculated by the regression statistical analyses using the
linear model (upper) and exponential model (lower).
In the summer months in North America, eggs are laid on
milkweed plants. The larvae feed exclusively on milkweed leaves, making the
abundance of monarch butterflies critically dependent on milkweed
availability. The spread of GM crops and the concomitant use of herbicides
however, are threatening the milkweeds survival and their numbers have been
steadily decreasing. Milkweed commonly grows among
maize and soya, of which 23 and 92 percent are currently glyphosate tolerant. Studies
assessing milkweed populations in Iowa recorded a 90  and 79 percent (unpublished)
loss between 1999-2009 and 2000-2009 respectively. The authors go on to
speculate that with such widespread glyphosate usage, milkweed may
almost completely disappear from crop lands altogether.
Additional increases in biofuel production and development led
the authors to estimate a total loss of milkweed habitat to be 56 million
hectares, more than one fifth of the north eastern US breeding range. The
study concludes that this huge decrease in breeding habitat must be significant
in accounting for dwindling butterfly numbers.
is not the first time that scientific studies have warned against the effects
of GM crops and glyphosate herbicides on monarch butterfly numbers. Back in
1999, three years after the launch of GM Bt corn into the US market, a report in Nature documented that Bt corn pollen, when dusted over milkweed plants, reduced the survival of larvae by up
to 44 percent . Although performed under artificial conditions, it is
a proof-of principle study showing the potential harm of such products on
companies have argued that exposure to Bt corn pollen may be minimal and thus
have negligible effects on butterfly numbers. It is much harder to argue
against the harmful effects of the rapid disappearance of the only monarch
butterfly larval food source.
authors also blame extreme weather conditions, as well as illegal over-logging
in Mexico as contributors to the declining population
numbers. One study found a 44 percent decline in high quality forest area due
to logging degradation from 1971 to 1999 across a 40,000 ha area . Increasing
the size of nature reserves by the Mexican government has stemmed the logging,
but has not put an end to the practice completely.
This study adds further evidence to the harmful
effects of glyphosate to the ecosystem and the natural diversity of insects
and plants alike (see  Scientists Reveal
Glyphosate Poisons Crops and Soil. GM meltdown continues, SiS 47,  Glyphosate Tolerant
Crops Bring Diseases and Death, SiS 47), and its devastating health impacts (see  EU
Regulators and Monsanto Exposed for Hiding Glyphosate Toxicity, SiS 51). It is the most popular herbicide in the US, and as a consequence it will have far reaching effects on the environment.
A study released by the U.S. Geological
Society last month assessed the presence of glyphosate in air and rain.
Detection ranged from 60 to 100 percent, highlighting how exposed the environment
and people of the US are to this herbicide . Its
use needs to be urgently curbed to prevent any further damage to health and the
There are 3 comments on this article so far. Add your comment
|Rory Short Comment left 19th September 2011 18:06:09|
It is in a sense pointless opposing each of the aberrations that emerges because until we change our basic orientation toward what lies outside of ourselves to one of cooperation and away from one of exploitation, conditions such as those described above will continue to proliferate until the consequences of our own destructiveness destroys us too.
|Todd Millions Comment left 22nd September 2011 09:09:38|
I live on a major monarch path,with pastures containing choice feed-showy milkweed.I've not seen a monarch in 3years and the milk weeds are showing stress and poor reproduction.Granted the clime of the last two years has being poor for both.Some analouge species from high land nortern states do seem to be filling this pollenatiors gap-but not as fully,they simply don't reproduce quickly enough.
|Chef John Rasmussen Comment left 31st October 2012 16:04:50|
My wife and I served as Monarch butterfly counters at Point Pelee Provincial Park in Ontario, Canada.
I recall in the mid 1980's when Monarch migration peaked, trees filled with Monarchs rest overnight.
In early morning sunlight Monarchs open & close wings until a magical moment when colorful Monarchs fly in mass to cross open water of Lake Erie. It looks like the "leaves of the trees" turn orange and fly away leaving an almost leafless tree.
It is very sad that chemical companies justify
toxic chemicals as harmless when in fact toxic
chemicals used on corn and soybean can kill
majestic Monarch butterfly by destroying milkweed habitat, the main Monarch food source.