|
Slate Magazine January 30,
2014
Read the whole article
here:
http://www.slate.com/articles/health_and_science/science/2014/01/monarch_butterfly_decline_monsanto_s_roundup_is_killing_milkweed.html
The Missing Monarchs
Monsanto’s Roundup and
genetically modified crops are
harming everybody’s favorite
butterfly.
By Warren Cornwall
Feeding on a weed seems like a
good evolutionary bet. And for a
long time, it worked well for the
monarch butterfly.
The butterfly’s life
cycle is exquisitely synchronized
to the seasonal growth of
milkweed, the only plant its
larvae will eat. In a game of
hopscotch, successive generations
of monarchs follow the springtime
emergence of milkweed from Mexico
as far north as Canada. The hardy
plant once flourished in
grasslands, roadsides, abandoned
lots, and cornfields across much
of the continent. It fueled a
mass migration that ended each
winter with more than 60 million
butterflies converging on pine
forests in the Sierra Madres.
Then came Roundup.
The number of monarchs
reaching Mexico has been falling
for years, and it has now reached
the lowest level on record. The
World Wildlife Fund announced
Wednesday that butterflies this
winter were found in 1.7 acres
across 11 sanctuaries, down from
a high of 45 acres in 1996. If
you want to know a main reason
why, look no further than your
corn chips and ethanol-spiked
gasoline.
The monarch population sank
while agriculture boomed. More
than a million acres of Upper
Midwest grassland have been
plowed under in recent years for
corn and soybean fields—a
rate of loss comparable to
deforestation in places like
Brazil and Indonesia. Demand for
these crops has surged with the
rise of biofuels. At the same
time, technology enabled farmers
to squeeze ever more from each
acre. For monarchs, the most
important development was Roundup
Ready corn and soybeans.
Since the turn of the century,
these genetically modified crops
have risen to dominance in the
Midwest. Designed to withstand
dousing from the Monsanto
company’s Roundup weed
killer, the plants enabled
farmers to swiftly kill competing
weeds, including milkweed, while
leaving their crops untouched. In
2013, 83 percent of all corn and
93 percent of soybeans in the
United States were herbicide
tolerant, totaling nearly 155
million acres, much of it in the
Midwest.
It’s no coincidence
monarchs faltered at the same
time. Karen Oberhauser, a
conservation biologist at the
University of Minnesota, and a
colleague estimated that as
Monsanto’s Roundup Ready
corn and soybeans spread across
the Midwest, the amount of
milkweed in farm fields fell by
more than 80 percent. Oberhauser
determined that the loss of
milkweed almost exactly mirrored
the decline in monarch egg
production.
“We have this smoking
gun,” Oberhauser said.
“This is the only thing that
we’ve actually been able to
correlate with decreasing monarch
numbers.”
Soon there will be essentially
no monarchs on cropland in the
corn belt, according to some
estimates. Already, Iowa farmland
has lost more than 98 percent of
the milkweed that was once there,
according to Iowa State
University biologist John
Pleasants, who worked with
Oberhauser. He’s seen
firsthand the transformation as
he has studied cornfields during
the past decade and a half.
Before Roundup, patches of
milkweed grew among the corn and
along the edges of fields. After
the herbicide—nothing but
corn.
This year’s dismal
turnout of monarchs has other
factors to blame as well. There
have been two years of unusual
spring weather in the United
States. In 2012 it was hotter
than normal, and the following
year it was colder, disrupting
the insects’ northward
migration. Illegal logging has
whittled away at monarchs’
winter habitat. But nothing can
match the lost milkweed in the
Midwest, birthplace of roughly
half of all the monarchs east of
the Rockies, said Chip Taylor, a
University of Kansas ecologist
who runs Monarch Watch, a program
that monitors monarch
populations: “The scale of
loss is fantastic.”
Monsanto emphasizes that loss
of milkweed to herbicides
isn’t the only culprit. Tom
Helscher, Monsanto’s
director of corporate affairs,
notes that a 2011 study found
monarch numbers hadn’t
fallen at sites in New Jersey and
northern Michigan.* (Taylor and
other monarch scientists dismiss
the study because it looked at
populations where milkweed is
still relatively abundant.) And,
Helscher said, butterfly
conservation needs to be balanced
with “society’s need to
improve productivity in
agriculture.”
No one expects that
agribusiness will give up
efficient, lucrative, and potent
tools. Instead, butterfly
advocates are hoping the industry
will throw some money and
marketing savvy behind campaigns
to get people to plant more
milkweed elsewhere. Taylor last
year started marketing tiny
milkweed seedlings to gardeners.
He sold 20,000 and is gearing up
to double or triple that this
year. But he acknowledges
it’s a fraction of
what’s needed.
This doesn’t mean the
monarch is about to go the way of
the passenger pigeon.* The
butterfly, which is also found in
Hawaii, Australia, New Zealand,
Spain, and Portugal, still
numbers in the millions.
It’s not a candidate for the
Endangered Species Act. But
there’s concern that the
epic mass migration to Mexico, a
natural wonder, could
disappear.
The success of this
transcontinental trip could
depend on a critical mass of
butterflies, said Oberhauser. The
massive gathering might help
protect against predators, much
as tiny fish seek safety in huge
schools, she said. But if there
aren’t enough butterflies,
the tactic might not work. Huge
clusters of butterflies could
also help them stay warm and save
energy as they wait for spring to
arrive.
A smaller population can also
have more trouble recovering when
other problems strike, like
droughts or heat waves. As the
climate changes, earlier springs
might throw off the intricate
timing between monarchs and their
food. That happened in 2012, when
unusually warm weather caused
monarchs to migrate north before
most of the milkweed had emerged.
Taylor’s worries that by
midcentury, the biggest threat to
the migration will be that Texas
is just “too bloody
hot.”
Oberhauser’s immediate
concern is at once more practical
and more romantic. She worries
that as monarchs get harder to
find, people will lose a popular
link to the natural world—a
gateway drug for nature
lovers.
How many kids in classrooms
around the country have watched a
plump caterpillar become a
jade-green capsule the size of a
peanut shell, then a monarch
butterfly? As a child I saw the
drama unfold in an aquarium in my
family’s living room in
Idaho. It was magical to see the
subject of all those
children’s books and
metaphors of transformation given
flesh.
Flash forward 30 years, and I
resolved to repeat this monarch
ritual with my children. I led
them into a patch of milkweed
plants in a Vermont field,
confident that we would quickly
wrangle a half-dozen
caterpillars. Several hours
later, we had one hostage.
Even with the dismal winter
numbers, there’s still hope
for summer caterpillar hunters.
Monarch numbers will probably
stay lower than they were in a
weedier world, but the
butterflies lay enough eggs that
they can bounce back a bit in
just one season, Taylor said. Now
he’s watching the spring
weather forecast in Texas and
crossing his fingers.
|
