Monarch Population Drops 97% in 20 Years

December 12, 2018 at 1:40 pm




Researchers say plummeting monarch population is a marker for a larger “Insect Apocalypse”






In decades past, millions of monarch butterflies flew to Southern California each year to spend the winter. This year, researchers estimate only 30,000 in the region, an 97% reduction from just two decades ago.

Revered for their majestic beauty, monarchs are seen as a marker for a broader ecological phenomena some are calling the “Insect Apocalypse.”

A German research group estimates a decrease of up to 82% of all flying insect over the last three decades.

Unable to tolerate the cold, many migrant insects fly to Southern California for the winter, where the low in December averages a balmy 48 degrees Fahrenheit.  

Most migrant butterflies travel only one way, breeding new generations to make the return flight.

The big, strong monarch is the only species in which individual butterflies make a two-way journey, some totaling 3,000 miles.

In the 1980’s, a conservation group called the Xerces Society, counted 4.5 million monarchs overwintering across Southern California.  This year’s count estimates as few as 30,000.

“We had a lot of reason to suspect that it was going to be a bad year, but we were shocked at just how bad,” said Emma Pelton, Xerces Society Conservation biologist told The Guardian.

Fluctuation from year-to-year can be expected, but the continuous drop-off is reason for concern, she says.

“It is in the context that the population has already declined 97%. So, it’s OK if you have millions of butterflies and they drop down a little bit – that’s not a huge deal. But if you have 200,000 butterflies to begin with and you have a bad year? Now we only have 30,000 left.”

Natural Bridges State Park, in Santa Cruz, California, found 8,000 monarchs overwintering in the trees just two years ago.  This year, only about 1,000 can be seen, showcasing the alarming trend.

Researchers cite many factors including:  habitat loss and fragmentation in breeding and overwintering locations, increased use and spread of pesticides, drought, and severe weather.

Monarchs are losing the trees they travel to hibernate in year after year

Climate change is also widely pointed to as playing a major role in a decrease of flying insects all over the world.

The decline of the monarch population is like the canary in a coal mine, alerting us to the consequences of our actions, argues Anurag Agrawal, an ecology and evolutionary biology professor at Cornell University in his blog.

The monarchs’ unique migration pattern makes them easy to track and gives us insight into the “health of our entire continent,” he say.

“We have to take a step back and ask ourselves the harder questions that none of us want to deal with.” 

When their primary food source, milkweed, begins to grow in the spring, the monarchs will start their journey north again.  The females will lay their eggs on the plant as they go, instinctively providing opportunity for another generation to exist.  


While planting milkweed and restoring other native plants can help, we’ve discovered that saving a species isn’t that simple .  Perhaps the next generations of humans will take notice and make better decisions for butterflies, and all creatures.

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