Enviro-Stewardship: Butterflies and Milkweed

Once a month, I turn the blog over to Dad for the Environmental Stewardship column that he writes for local church newsletters. The rest of this post (including the footnote this time) is the July column by John Berge:

While I have told this story before, the recent announcements of decreases in the iconic Monarch Butterfly population make it worthwhile to retell it.

Several years ago, two little girls with newly gifted butterfly nets came up to me while I was working in the yard and plaintively asked where all the butterflies had gone. I showed them the little signs in a neighbor’s yard saying the lawn had been sprayed with herbicide and insecticide and then pointed to all the other similar signs in the neighborhood.  I then led them to our back yard and my wife’s “natural area” where we saw a couple of butterflies that were too quick to be caught.

My little “teaching moment” was mostly on insecticides. Butterflies and their wild looking, hairy or horned larvae (caterpillars) are insects and were being killed by those lawn sprays.

Collin O’Mara, President of the National Wildlife Federation, has recently quoted Mexican officials that the population of monarch butterflies over-wintering in Mexico dropped 14.8% over the previous year, continuing the trend that has seen a 90% drop over the last two decades. These estimates are based on the area covered by these butterflies, which can number anywhere from 10 to 50 million per hectare (2.471 acres).

Suggested causes of this precipitous drop include: hurricanes, which have always been present; degradation of habitat in the Mexican mountains due to lumbering; increased use of pesticides and other toxic chemicals, as I mentioned to those two young ladies; global warming; and loss of milkweed habitat in the United States. We, as environmental stewards, have some power over the latter three causes.

Many butterflies, in their caterpillar stage, are more finicky eaters than any child you have ever known. Monarch caterpillars eat only milkweed leaves*. So the indulgent parents lay their eggs only on milkweed plants (Asclepias species). If they can’t find them, there goes one of the several generations that make up the round trip from northern USA and Canada to Mexico and back.

We have two varieties of milkweed in our yard and do occasionally see the monarchs flying around. The plants don’t always grow where I want them, so I ignore the second half of their name and let them grow almost wherever they want. If all gardeners would include a few milkweed in their gardens and minimize their use of pesticides, two of the threats to the monarchs could be eliminated.

Another butterfly larva that is a finicky eater is that of the Karner Blue butterfly. It feeds only on the wild lupine that is found in open, sunny areas with sandy soil such as found in some areas of northern Wisconsin and Upper Michigan. I know of no Karner Blues in our area of the state, but people who have second homes up north containing such habitats should be good environmental stewards by planting and encouraging the native lupine.

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* This is true for the first four instars (stages between molts) of the caterpillar's growth; but some people in Texas, where milkweed has virtually disappeared, have reported that fifth instar caterpillars, the last before forming a chrysalis, will in desperation feed on the skin of melons.