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| Micah Lidberg |
ON the first of November, when Mexicans celebrate a holiday called the
Day of the Dead, some also celebrate the millions of monarch butterflies
that, without fail, fly to the mountainous fir forests of central
Mexico on that day. They are believed to be souls of the dead, returned.
This year, for or the first time in memory, the monarch butterflies
didn’t come, at least not on the Day of the Dead. They began to straggle
in a week later than usual, in record-low numbers. Last year’s low of
60 million now seems great compared with the fewer than three million
that have shown up so far this year. Some experts fear that the
spectacular migration could be near collapse.
“It does not look good,” said Lincoln P. Brower, a monarch expert at Sweet Briar College.
It is only the latest bad news about the dramatic decline of insect populations.
Another insect in serious trouble is the wild bee, which has thousands
of species. Nicotine-based pesticides called neonicotinoids are
implicated in their decline, but even if they were no longer used,
experts say, bees, monarchs and many other species of insect would still
be in serious trouble.
That’s because of another major factor that has not been widely
recognized: the precipitous loss of native vegetation across the United
States.
“There’s no question that the loss of habitat is huge,” said Douglas
Tallamy, a professor of entomology at the University of Delaware, who
has long warned of the perils of disappearing insects. “We notice the
monarch and bees because they are iconic insects,” he said. “But what do
you think is happening to everything else?”
A big part of it is the way the United States farms. As the price of
corn has soared in recent years, driven by federal subsidies for
biofuels, farmers have expanded their fields. That has meant plowing
every scrap of earth that can grow a corn plant, including millions of
acres of land once reserved in a federal program for conservation
purposes.
Another major cause is farming with Roundup, a herbicide that kills
virtually all plants except crops that are genetically modified to
survive it.
As a result, millions of acres of native plants, especially milkweed, an
important source of nectar for many species, and vital for monarch
butterfly larvae, have been wiped out. One
study showed that Iowa has lost almost 60 percent of its milkweed, and
another found 90 percent was gone. “The agricultural landscape has been sterilized,” said Dr. Brower.
The loss of bugs is no small matter. Insects help stitch together the
web of life with essential services, breaking plants down into organic
matter, for example, and dispersing seeds. They are a prime source of
food for birds. Critically, some 80 percent of our food crops are
pollinated by insects, primarily the 4,000 or so species of the flying
dust mops called bees. “All of them are in trouble,” said Marla Spivak, a
professor of apiculture at the University of Minnesota.
Farm fields are not the only problem. Around the world people have
replaced diverse natural habitat with the biological deserts that are
roads, parking lots and bluegrass lawns. Meanwhile, the plants people
choose for their yards are appealing for showy colors or shapes, not for
their ecological role. Studies show that native oak trees in the
mid-Atlantic states host as many as 537 species of caterpillars, which
are important food for birds and other insects. Willows come in second
with 456 species. Ginkgo, on the other hand, which is not native,
supports three species, and zelkova, an exotic plant used to replace elm
trees that died from disease, supports none. So the shelves are nearly
bare for bugs and birds.
Native trees are not only grocery stores, but insect pharmacies as well.
Trees and other plants have beneficial chemicals essential to the
health of bugs. Some monarchs, when afflicted with parasites, seek out
more toxic types of milkweed because they kill the parasites. Bees use
medicinal resins from aspen and willow trees that are antifungal,
antimicrobial and antiviral, to line their nests and to fight infection
and diseases. “Bees scrape off the resins from the leaves, which is kind
of awesome, stick them on their back legs and take them home,” said Dr.
Spivak.
Besides pesticides and lack of habitat, the other big problem bees face
is disease. But these problems are not separate. “Say you have a bee
with viruses,” and they are run-down, Dr. Spivak said. “And they are in a
food desert and have to fly a long distance, and when you find food it
has complicated neurotoxins and the immune system just goes ‘uh-uh.’ Or
they become disoriented and can’t find their way home. It’s too many
stressors all at once.”
There are numerous organizations and individuals dedicated to rebuilding
native plant communities one sterile lawn and farm field at a time. Dr.
Tallamy, a longtime evangelizer for native plants, and the author of
one of the movement’s manuals, “Bringing Nature Home,” says it’s a cause
everyone with a garden or yard can serve. And he says support for it
needs to develop quickly to slow down the worsening crisis in
biodiversity.
When the Florida Department of Transportation last year mowed down
roadside wildflowers where monarch butterflies fed on their epic
migratory journey, “there was a huge outcry,” said Eleanor Dietrich, a
wildflower activist in Florida. So much so, transportation officials
created a new policy that left critical insect habitat un-mowed.
That means reversing the hegemony of chemically green lawns. “If you’ve
got just lawn grass, you’ve got nothing,” said Mace Vaughan of the
Xerces Society, a leading organization in insect conservation. “But as
soon as you create a front yard wildflower meadow you go from an
occasional honeybee to a lawn that might be full of 20 or 30 species of
bees and butterflies and monarchs.”
First and foremost, said Dr. Tallamy, a home for bugs is a matter of
food security. “If the bees were to truly disappear, we would lose 80
percent of the plants,” he said. “That is not an option. That’s a huge
problem for mankind.”
