It's not too late

Could you use some good news? Here’s some: last Thanksgiving the population of Western monarch butterflies counted in California increased by over 100-fold, from fewer than 2,000 butterflies counted in 2020 to 247,237 in 2021. 

 

Monarchs roosting for the winter

That’s not full recovery. Some experts estimate we’ve lost 80 percent of monarchs in 20 years. But it’s nice to know how resilient these butterflies can be.

    Western monarchs are genetically indistinguishable from the Eastern kind. It’s just that monarchs that live west of the Rockies overwinter in California and migrate to the Northwest for the summer. The ones that live east of the Rockies overwinter in central Mexico in the Monarch Butterfly Biosphere Reserve. Around this time of year, as the weather warms, they start their flight to Texas.

 

During the spring three or more successive generations of monarchs journey through the Southeast to the northern states and southern Canada where they spend the summer. Then in August and September another new generation starts to flutter all the way back to Mexico, a journey that takes up to two months (this Google Earth video illustrates it all). 

    Migration is necessary because monarchs can’t survive northern winters. In the mild, humid winter climate of Mexico’s Sierra Madre mountains, they roost in oyamel fir trees (here’s another fascinating video), packing together to stay warm. 

     With this successful life cycle evolved over the millennia, why did the monarchs suddenly start to disappear? The first obvious culprit was glyphosate (Roundup) sprayed on agricultural fields. Glyphosate use surged in the 1990s with the introduction of genetically modified Roundup Ready crops that resist the herbicide spray while it kills the weeds around them. 

Monarch caterpillars need to eat milkweed to survive. Milkweed toxins ingested by monarchs make them poisonous to predators but don't hurt the monarchs.

     Some of those weeds/wildflowers are native milkweeds. Monarchs need to lay their eggs on milkweeds to reproduce. Instead of finding milkweeds offering nectar and forage for their caterpillars alongside every field, the migrating butterflies now had to cross vast milkweed deserts in agricultural regions of the U.S.

Eastern native swamp milkweed is easy to grow and provides a lifeline for monarchs

     A recent meta-analysis by a team at Michigan State University, using data from thousands of volunteer monarch counts, found that glyphosate, habitat loss, and climate change have all contributed to the monarchs’ decline. In recent years, hotter weather in their northern range seems to have been a major factor.

     When we hear that climate change is the reason that species are dying out, it can sound hopeless. We’re not moving fast enough to save ourselves; how are we going to save the monarchs? But as the scientists point out, when migrating monarchs are stressed by high temperatures, that’s when they especially need lots of milkweeds and other native flowers for nectar along their path so they can stop off and refuel or lay eggs.

 

Migrating monarchs need other flowers too for energy from nectar

 
     The surge in Western monarchs shows that the monarch population has the capacity to rebound suddenly and dramatically. And the fact that thousands of human well-wishers are already helping encourages me too. This year let’s redouble our efforts to plant for native insects, and let’s be sure to include milkweeds in the mix.

 

Common milkweed is another good choice. It's a spreader.