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Date: Thu, 11 Jul 2019 09:55:09 -0400
From: 'Garry Kessler' via MassLep <masslep...>
Subject: [MassLep] More bad news for insects

A recent article...


Butterfly populations in Ohio have dropped by over a third in the past
two decades, scientists have revealed.

Each year since 1996, overall populations of the 81 butterfly species
looked at in the study published in the journal PLOS ONE dropped by an
average of 2 percent, or 33 percent in total. Three times as many
species are seeing populations fall compared with those experiencing
positive trends.

In the biggest ever insect monitoring program carried out in North
America, the team looked at data collected weekly by volunteers in
24,405 butterfly surveys. The citizen scientists monitored 104 sites
between the months of April to October, from 1996 to 2016. The 116,100
km2 of land over which the Midwestern state stretches provides a variety
of habitat types, from prairie-like areas to mountains and forest.

Tyson Wepprich, a co-author of the study who researches insect
populations at Oregon State University, told Newsweek: "There is a lot
of worry about insect declines, but very little data outside of a few
long-term monitoring programs in Europe. We use the best systematic
monitoring dataset for insects in North America to estimate the rate of
change in butterfly abundance."

The Monarch butterfly was found to be the only migratory species in
decline, the team found. Forty of the species saw no significant change.

Climate change, as well as the degradation of habitats and changes to
farming methods, could explain the drop, the authors wrote.

"Species with more northern distributions and fewer annual generations
declined the most rapidly," Wepprich explained in a statement. This
could be because they can't withstand the heat as temperatures in Ohio rise.

The findings add to an already bleak outlook for insects, as past
research on 452 species suggests numbers have dropped by 45 percent
globally over the past 40 years.

Past studies have shown the migratory eastern North American monarch has
declined by more than 85 percent, while the western North American
monarch has dropped by more than 95 percent. Wepprich said in a
statement some of the rarest butterflies are among those falling sharply.

Butterflies provide a useful insight into the threats faced by insects
in general, as they contend with the same pressures from factors like
climate change and habitat loss. And as most people like butterflies
more than other insect species, it is easier to ask the public to take
part in monitoring programs, the authors explained.

The drop is similar to the rates found in the UK, Netherlands, and
Spain, Wepprich told Newsweek.

"Although these declines are not as drastic as others being reported
recently, this monitoring program is built to detect abundance changes
and shows that insect declines are not just something to worry about in
Europe," he said.

Wepprich told Newsweek it is tough to estimate trends in populations
because insect counts fluctuate depending on the season they are active,
the flowers that happen to be in bloom that week, or by the weather in a
particular year being good or bad for the population.

"We overcame this problem by using statistical methods that have been
developed by researchers for other monitoring programs," he said.

"I was surprised that some common species that are adapted to live in
human-dominated habitats, like agricultural or urban areas, were
declining," said Wepprich.

"Usually people wouldn't worry about insect pests, like the Cabbage
White, but we think this shows that the populations of some of the
hardiest butterfly species may be affected by environmental changes."

Highlighting the limitations of the work, Wepprich said the team didn't
have the data to uncover how other insects are faring in Ohio, and
whether the trends would apply to other parts of the world.

Wepprich urged decision-makers to think of insects when they plan public
spaces like parks, farmland, roadsides, school grounds and other public
areas where planting native flowers and food plants can be done over
large areas at a time.

While those actions would have a larger impact than anything individuals
can do, Wepperich said he still avoids using pesticides in his yards and
has replaced some grass with native plants.

"I'm enjoying seeing native bees and other pollinators visit. Especially
in urban areas, these small patches can benefit butterflies and other
insects more than grass lawns," he said.

Garry Kessler

Westborough, MA

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