The Monarch
Butterfly, a species so widespread and beloved that it is the state insect of seven states, West Virginia, as well as Alabama, Idaho, Illinois,
Minnesota, Texas and Vermont, is severely threatened.
Bear with me here.
Much of this post may remind you of your fourth grade science fair
poster on the life cycle of butterflies.
Though the information may not be new, perhaps it will provide a little
refresher course in the extraordinarily complex life of this lovely and fragile
insect, and make clear why we all should be watching out for the
Monarchs.
Adult butterflies live but a few weeks. Consuming only
nectar from flowers, they search meadows, roadsides and gardens for the best
sources. Before they die, they seek out
the proper food source for the next generation and lay their eggs on those
plants. With luck, the caterpillars hatching from
these eggs will emerge at just the right time, when the temperature and food
supply are optimum. Caterpillars eat only leaves, each species favoring a common
plant or tree of the region. When cold
weather comes, the caterpillars of most butterflies begin to change, becoming
pupae which will live in a kind of state of suspended animation until they come
forth as adults in the spring.
But what if the optimum environment begins
to change? What if the temperatures become less predictable? What if food sources disappear?
One butterfly species, the familiar orange and black Monarch,
faces all these challenges, partly because it has a very different strategy for
survival. This butterfly responds to the
onset of cold weather by migrating. Each
October millions of Monarchs begin their trip south across the Eastern and
Midwestern states following a very specific migratory pattern. A smaller population on the west coast of
North America travels a separate route down through southern California. All are headed to Mexico, to a region high in
the Sierra Madre Mountains. There, the
overwintering insects congregate in the Oyamel Fir forests. They hang in great clusters, with perhaps 100,000
individuals per tree. These colonies
blanket the mountaintops, an extraordinary sight which has generated a steady
tourist industry for the region. In
March, warmer weather triggers a reverse migration. The Monarchs, in their millions, gradually drift
up from the trees and head north, following the same routes traveled by
countless previous generations.
These age old flight paths are based on where the
necessary food sources will be found.
Monarch caterpillars can eat only plants from the milkweed family. A wildflower, this tall, fuzzy-leafed plant
with umbels of fragrant flowers is native throughout North America. Common along roadsides and in fields, the
plant self-sows easily. Each plant
produces a multitude of delicate seeds equipped with a silky tendrils which
allow them to float far on the slightest breeze. Hardy and adaptable, milkweed thrives in dry
or wet conditions, at various latitudes and altitudes, and competes quite
successfully with all the other plants in its vicinity. It grows everywhere, providing a dependable
food source for the Monarch all along
its migratory routes.
The Monarch’s very specialized reproduction pattern is attuned
to its migratory habit. The generation
of overwintering Monarchs that leaves Mexico in March is called the first
generation. These butterflies fly north,
and when attracted by a place with plenty of milkweed, stop to lay their eggs before
they die. The second generation matures
and continues to migrate north, following the milkweed as it blooms. Then the third generation caterpillars hatch,
mature and head out for the milkweed buffet even further north.
In a single summer there may be as many as four
generations heading steadily north, following the milkweed, all the way into
southern Canada. But at the end of
summer, as the cold weather approaches, the final generation develops very
differently. Though these orange and
black beauties look just like their parents and grandparents, the do not mate
or develop eggs. Their bodies become
extremely efficient at converting and storing fat. They’ll need it, because this is the generation
that will make the entire return trip, 2,500 miles, all the way back to Mexico.
It is a complex and beautiful system for survival, one that
has allowed the species to flourish even when a change in climate or habitat
occured in some part of its expansive range.
But about 20 years ago scientists began to notice a significant disruption
of the Monarch’s migrating patterns followed by an alarming decrease in its population. It finally became evident that the problem
was milkweed, or the lack of it. The Monarch’s food source was disappearing. Areas where once the plant was abundant were
now free of all weeds, including the milkweed.
The fields and roadsides of America’s agricultural lands were now being chemically groomed to allow only specific crops to survive, and the agent was
the herbicide Roundup. Though Roundup
had been around for a while, it was in the 1990s that crop plants were
developed to be resistant to the effects of glysophate, the principal chemical
in Roundup. ‘Roundup Ready’ corn, cotton, and soybeans were genetically
modified to withstand the effects of the herbicide. So a farmer could spray his fields and the
chemical would eradicate all plants except the genetically modified crop
plants. It seemed a terrific tool for
farmers to save time and labor and better ensure good crop survival. But every year millions of acres received the
treatment, eradicating milkweed all along the Monarch’s migration routes.
In 2013-2014 the Monarch population has reached a new low
of 30 million butterflies, half of the number recorded for 2012-2013, and a
drastic decline from the long term average of 350 million. Scientists estimate the population by
determining the total area, in hectares, covered by the overwintering colonies. This number is then multiplied by the number
of individuals typically found clustered in a hectare. Last
winter the overwintering population covered less than 1 hectare (about 2.5
aces) compared to over 20 hectares a scant twenty years ago.
Severe weather across North America in recent decades has
certainly been a factor in the Monarch’s struggles. Deforestation of habitat in Mexico has also
played a part. Scientific teams and
environmental groups have long been working to preserve the areas in Mexico
where Monarchs gather. But it is the
lack of food throughout the entire migration route that has caused the Monarchs’
numbers to plunge to dangerous levels. The only way to limit the Monarch Butterfly's decline is to return milkweed to its habitat.
Below are links to connect you with information
about how we all can help. Consider participating in one of the citizen scientist programs and help collect important data on Monarch migration. Or find out about conservation organizations which can get you set up to hand rear Monarch caterpillars until they can be released as adults. Learn out about legislation to restrict use of glysophate along roadsides and highways or other non-agricultural lands. Above all, plant milkweed! Plant milkweed in masses if possible. Anyone with a bit of yard, or
even a balcony container garden, can encourage the growth of milkweed and begin watching out for the Monarchs.
Find out more about Monarchs:
