Let us make it
really simple. They did not die off in Mexico. They are failing in North America. Their habitat is strictly along field fence rows where the milkweed grows. All these
fence rows are certain to be the main line of defense for protection from windblown
pesticide sprays. It is reasonable to
conclude that the buildup of pesticide in the environment has gone critical and
the majority is no longer making it out of their pupae.
This is very bad
news because it powerfully supports the general collapse of a broad spectrum of
our insect population and the looming collapse in general fertility of our soils. It really has to be considered however
forgiving our soils are.
The linkage may
not be real, but the fact is that we are rolling the dice without certainty
that these conjectures are wrong.
An aside though,
it is time to dismiss biological drivers for bees and butterflies. It has gone on too long for a mere biological. Those always infect and then die off as the
population adjusts.
Why monarch
butterflies’ numbers are in freefall
VIDYA KAURI
Jul. 31 2013,
In an average year, 350 million monarch butterflies are seen wintering in Mexico. This winter, there were only about 60 million – a difference of more than 80 per cent, according to an official count by the World Wildlife Fund and the Mexican government.
Those numbers – the lowest in 20 years of recorded
history – have experts wondering if, and how, monarchs can bounce back from
this significant decline in their population.
For Canadians, the reality hit home in July when
butterfly lovers and naturalist clubs began recording their first monarch
sightings of the year, about six weeks later than usual. Monarchs leave their
breeding grounds in Ontario and the United States each fall, heading south to
Mexico through the midwestern United States. They leave Mexico again in early
March, returning to their northern breeding grounds.
The first monarch butterfly sightings are usually
recorded in the southernmost tip of Ontario in early June. This year, the first
sightings occurred in mid-July – a time when the butterflies should already be
nestled in their breeding grounds. The number of butterflies being recorded is
also dismally low: In regions where more than 100 monarchs were spotted in the
province last year, fewer than five have been observed this year.
Monarch populations have been gradually declining
over the last eight years, according to Donald Davis, chair of the Monarch
Butterfly Fund, who has been tagging monarchs since 1967. The organization,
dedicated to the conservation of monarch butterflies, is comprised of
academics, butterfly lovers and environmentalists.
“I have never seen them this low,” Mr. Davis says.
“Ever. In all my years of studying monarchs.”
Experts don’t know for sure why the monarch is so
late to appear this summer or why their numbers are dwindling. One reason could
be a loss of habitat, Mr. Davis says. Monarchs rely exclusively on the milkweed
plant to reproduce, but over the years milkweed has been treated aggressively
with pesticides for being a noxious weed.
Another potential factor could be the drought in the
spring and summer of 2012 in the central United States, Mr. Davis says. “The
butterflies don’t do well or reproduce in drought.”
Last year, monarchs showed up early in Ontario,
after migrating through drought conditions. They arrived before milkweed was
even out of the ground.
The combination of drought and loss of milkweed not
only would have affected the monarchs’ ability to reproduce, but also to store
fat reserves in their abdomens for the journey back to Mexico, Mr. Davis says.
Dry conditions in some parts of Ontario last fall would not have helped the
monarchs either, he adds.
This year, the migration back to Ontario wasn’t any
easier for the monarchs – already low in numbers – with a chilly spring all
across the south. The cold-blooded insects are extremely sensitive to
temperature, says Elizabeth Howard, founder of Journey North, the organization
that tracks the monarchs’ migration through reports of first sightings across
the continent.
“They can’t even fly until their flight muscles are
55 degrees Fahrenheit [13 C]. So, they can’t even migrate. They are basically
stuck in their tracks by the cold,” she says.
Since a monarch’s life span is only about two to
four weeks – one migration can comprise several generations of the butterflies
– an entire generation is missing in Ontario.
“What that means is that each generation is not
producing very many monarchs,” Ms. Howard says. “The significant thing beyond
that is that fall migration starts in August. So, we’re looking at the breeding
season ending before the numbers really build.”
Ms. Howard says the monarchs need warmer
temperatures to make up their numbers. “This year is an extreme. Nobody knows
if they can recover from these levels. They may bounce back, but it doesn’t
look very good.”
The extremes in weather conditions, she adds, stem
from climate change. “I don’t think this is a stretch to say how this is an example
of how climate change is affecting a species.”
Mr. Davis expresses similar concerns and suggests
that a solution may be for people to create “monarch butterfly way stations”
with plenty of milkweed to help the butterflies stay healthy along their journey.
He is also encouraging people to report monarch
butterfly sightings onebutterfly.ca as
the sharing of information can be helpful.
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