The conspicuous decline of monarch butterflies has been in the news a lot lately. Exact numbers of individuals are hard to measure precisely, but this past winter appears to have seen the fewest butterflies EVER overwintering in Mexico.
Ever. That’s bad news.
Monarch butterflies, like bees, are pollinators and, in some senses, their unfortunate struggle is a reality for all native pollinators (we’ve written at length already about the plight of native bees). But, in other ways, the monarchs’ situation is special—their life cycles and migratory patterns are totally unique and they rely, for much of their lives, on a single food source. For these reasons, monarchs won’t be rescued by a general plan to aid pollinators. They need a particular strategy that recognizes their particular needs.
At the farm, Oxbow Fellow Nikki Hanson is helping to solve that problem. She is spending the summer at our Native Plant Nursery, testing different strategies for propagation as part of her Master’s research from the University of Idaho. We all hope her work will help scientists and activists dial in conservation efforts to give monarchs the support that they need.
To understand Nikki’s research, first you need to know a thing or two about monarch butterflies:
First, they LOVE milkweed. In fact, during their larval stage (ie., when they are caterpillars), it’s all they eat. Milkweed is a broad-leafed, sun-loving plant named for its milky, latex sap. This sap is toxic—but that’s WHY monarch caterpillars eat it. The cardenolide toxin in milkweed is safe for monarchs, but renders them poisonous to eat. Adult butterflies retain the toxins in their body that they consumed as caterpillars, and broadcast a warning to predators with their brightly patterned wings. Monarchs lay their eggs on milkweed plants to ensure their young have an ample food source. In short, monarch butterflies need milkweed.
Second, milkweed is getting harder and harder for monarchs to find. Milkweed grows best in open meadows under full sun, so they are actually quite well-suited to the fringes of agricultural fields, and even grassy roadsides. Where milkweed runs into trouble is with the indiscriminate spraying of herbicides, a normal practice on many farms and a weapon of crews in California (where Nikki is from) fighting to keep excessive roadside plant growth from contributing fuel to wildfires. Milkweed populations declined as much as 58% in some parts of the country between 1999 and 2010, coincident with an increase in the use of the glyphosate herbicide commonly paired with genetically modified corn and soy.
The cause and effect relationship between the declines of milkweed and monarch butterflies is easy to see. Although the loss of milkweed is just one of several problems plaguing monarchs, it is a simple one to focus on. Its causes are known, its implications are obvious and easy to understand, and there is one relatively straightforward step we can take: Plant more milkweed.
Nikki’s research is about how to grow milkweed efficiently. She is spending this summer growing two different milkweed species (showy milkweed and narrow leaf milkweed) with two different concentrations of fertilizer in three different container sizes. Eventually, she will be able to determine which growing conditions are best for each species, using two different measures for what’s “best.” One will be dry biomass—drying half of the plants and weighing them to measure which have grown most vigorously. The other will be plant viability—Nikki will plant out the other half of the milkweed and note its success growing in natural conditions. With both of these measurements, Nikki will hopefully be able to draw useful conclusions about how different propagation conditions affects a milkweed plant’s growth and viability.
Nikki is here at Oxbow through Mid-December, and is headed back to the University of Idaho in January 2016 for spring semester in her Master’s work. As an Oxbow Fellow, she is already committed to returning to the farm next summer to conduct a follow-up study on this year’s research. She is thinking of designing a study to measure milkweed’s ability to withstand cold and/or dry weather.
We are all excited at Oxbow about Nikki’s research. While monarch butterflies and milkweed are not native to the Snoqualmie Valley, they are both present in Eastern Washington and the measures being taken to boost their populations align with our efforts, as an organization, to support native pollinators. Formal research is just one component. We are also involved in a long-term project to restore the environment surrounding the farm with native plants, the favorite forage of native pollinators, grown right here in our Native Plant Nursery and kids, on school field trip and summer camp visits to the farm, learn about the important role native pollinators play in the ecosystem supporting our farm.
Do you want to be an ally to native pollinators? Planting your yard with native species is a huge way to help. The Million Pollinator Garden Challenge offers gardeners resources for planning pollinator gardens and the opportunity to register their home gardens on a nationwide map.
This article appeared in our newsletter June 29. Sign up to receive it.