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Heidi Shaffer, Published August 10 2009

Monarch populations may be decreasing

Data suggests that monarch populations in North America are decreasing.

“The number of monarchs going through this (life) cycle is only about two-thirds of what it was about 10 years ago,” said Chip Taylor, who heads Monarch Watch at the University of Kansas in Lawrence.

The program has up to 15,000 volunteers tagging butterflies, which the researchers use to monitor migration patterns.

When Monarch Watch started 18 years ago, the main focus was to educate the public and get them involved in a “citizen experiment,” Taylor said.

The program has since turned toward conservation.

A reduction of habitat in both the U.S. and Mexico is contributing to shrinking monarch populations. In addition, climate change is likely the cause of shifts in migration pattern, Taylor said.

Monarch habitat is lost at a rate of 9.4 square miles a day, Taylor said.

“Since we started doing this, we’ve lost habitat equal to the size of the state of Illinois,” Taylor said.

Gerald Fauske, a researcher at North Dakota State University, said monarch populations have declined, but it’s unclear if they are permanent or what the exact causes are.

“We only have about 15 years’ worth of good monarch population data, not enough to know whether the overall population trend is downward, but enough to know that yearly fluctuations can be extreme,” Fauske said.

Adequate habitat is available for monarchs in the U.S., and under favorable conditions, a population loss can be overcome, Fauske said.

But as unfavorable weather and population declines become more frequent, rebounds may be cut short by another loss, Fauske said.

“We do not even know if these extreme fluctuations are normal or a recent phenomenon caused by human activities, but we do know that every graph has a zero point,” Fauske said.


Readers can reach Forum reporter Heidi Shaffer at (701) 235-7311