The Garden Report: The Demise of the Monarchs
“What is a butterfly garden without butterflies?” — Roy Rogers
Two summers ago a friend from New York City visited our fair isle for a day, and as most city dwellers are, was stirred by the beauty of Block Island. She remarked that she had never seen so many butterflies before, and I remember thinking, gee, I’ve never seen so few.
Monarchs are of course our nation’s most iconic butterfly, and the most studied in elementary school science classes. The great annual migration of the monarchs each fall from the northern states down to the Oyamel fir forests in central Mexico which, clustered together they over-winter, provides scientists with a means to measure their population. Each year the number of acres occupied by the monarchs is counted. Forty-five acres were covered with the beautiful butterflies in 1996; this year there were a mere 1.65 acres.
The butterflies leave Mexico from the end of February through mid-March and then move through Texas and fan out for either an eastern migration or a western one. In Texas they will try to reproduce in what will be the first of four generations to be born. The final generation is the only one that will migrate back to Mexico.
One graph that I found showed that the decline over the years was one steady downward line and if the trend continues, it won’t be long until that line reaches the bottom axis of the graph, which, if you recall from high school math, means that there will be zero monarchs left.
There have been three factors at play in the decline of the monarchs. The most commonly blamed seems to be illegal logging of the forests in Mexico however, that county has undertaken major efforts over the past five years to stem the practice. Mexico is vested in doing its part to preserve the monarch.
Another factor is the weather. Severe storms and droughts may affect the monarchs anywhere. A prolonged winter may also take its toll. The butterflies need not only ample supplies of nectar to feed on, but specific plants on which to reproduce: those of the milkweed family. They are the only plants the monarchs will lay their eggs on, with the emerging larvae dependant on the nourishment from their leaves as they go on to the next stage in their development.
And that brings us to what is probably the most alarming factor, but one that we can actually do something about. That is loss of habitat. And it isn’t just in Mexico, it is all over the United States.
It is too bad that somehow most of our country’s native plants and wildflowers have earned the moniker: weed. Many of these so called weeds are vitally important to our ecosystems. But nonetheless, they have been deemed weeds and so, whether on farms or along road sides, or in our yards at home, we have a tendency to, well, get rid of the weeds.
The most drastic loss of habitat for the monarchs has occurred in our nation’s vast corn belt. Once rolling prairies filled with native grasses and wildflowers, countless acres have been plowed up and planted with corn and soybeans. The push for ethanol fuel alone has led to a huge increase in the numbers of acres devoted to corn.
Farms used to have some “messy” areas around the fields — filled with wildflowers that sustain our native pollinators, including butterflies. But now 90 percent of corn grown in this country is genetically modified and is called “Roundup Ready.” The plants have been genetically altered so that when the fields are treated with this powerful glycosphate herbicide manufactured by Monsanto, they will be resistant to the chemicals, but none of the “weeds” will survive.
So loss of habitat means, simply, that there is no longer either sufficient food for the monarchs to survive or to reproduce for those four generations it takes before the monarchs even have a chance to try to make it back to Mexico.
Fortunately there are things we can do to help the monarchs, right here at home. And fortunately there are organizations that are actively trying to educate the public and to get them involved. Much of that involvement is an attempt to bring back the milkweeds to our native landscapes.
There are some 110 species of milkweeds in North America. Milkweeds are perennials in the Asclepiadaceae family and there are species that are specific to each region. In Rhode Island, those include the common milkweed (Asclepias syriaca), butterfly weed (Asclepias tuberosa) and swamp milkweed (Asclepias incarnata).
The white latex-like sap or “milk,” that gives the plants their names is toxic to vertebrate herbivores (such as deer) due to the caodenolide alkaloids present. However, when the monarch larvae munch the leaves, they sequester the substance later in their exoskeletons and wings, making the resulting butterflies poisonous to potential predators.
It should be noted that the invasive black swallow wort (Cynanchum louiseae) we see in increasing amounts here on Block Island is also a species of milkweed. However, while the monarchs may lay their eggs on the plant, the emerging larvae will not eat it, causing them to die — a good reason to get rid of it.
Besides the all important milkweeds the adult monarchs need nectar plants to feed upon. Some of their favorites include the native Joe Pye weeds (including coastal Joe Pye weed, hollow Joe Pye weed and purple Joe Pye weed) and the native lance-leaf coreopsis. They are also fond of pale purple coneflowers (Ecchinacea pallida) zinnias, blazing stars, golden rods and sunflowers. All of these plants do well on Block Island, (although the deer do tend to munch on the coneflowers and blazing stars), so it is relatively easy to create a monarch “way-station” as monarchwatch.org calls it.
As to where to obtain the plants, Rhode Island is fortunate to have the organization Rhody Native, a joint venture between the R.I. Natural History Survey and the University of Rhode Island. This organization collects and then grows seeds from native plants and then makes them available to various nurseries to sell. There are two such nurseries in Wakefield: Clark Farms and Blue Moon Farm Perennials (opening for the season in early April). Here on Block Island, many of these plants can be (or will be) found at Goose and Garden off of Beacon Hill Road.
One needn’t even necessarily “garden” to help the monarchs. Simply leaving a few areas to grow wild along stone walls will help as they attract native wildflowers and get “messy.”