In the paper, Configuration and location of small urban gardens affect colonization by monarch butterflies, researchers conducted an observational experiment in order to see how urban gardens affect monarch butterfly migration, and how citizens and naturalists can more efficiently assist in the migration process. The main focus of these gardens was placement of milkweed species, where at least one Asclepias species was planted, either common, butterfly, swamp, or a combination thereof. The experiment took place on the east coast in the cities of Lexington and  Richmond, Virginia, and Berea, Kentucky. The experiment took place in 2017 and 2018, both years between the months of April- September. This period was split into April-July and June-September so that June and July had more data than the other months, as this is the peak butterfly migration period through this area of the US.

The experiment included 22 pre-existing registered Monarch Waystations, which were monitored in agreement with the property and land owners, and 15 gardens spread out that each had adjusted factors. Of the pre-registered Monarch Waystations, these were treated all the same, and were given the label of “structured” or “unstructured”, with “structured” meaning that the milkweeds were planted in an orderly array, and “unstructured” meaning they were mixed with other grasses, forbes, nectar-bearing plants, and other flowers. The gardens were set up in 5.5 x 5.5 meter plots, with three different set treatments. The first treatment was the “perimeter milkweeds”, where the flowers were placed in a 1 meter wide perimeter around the garden, evenly spaced out, with the other types of nectaring and foliage plants in the middle of the plot. The second treatment was essentially the inverse of that, referred to as the “interior milkweeds”, where the milkweeds were planted on the interior of the plot, evenly spaced, with the other plants along the perimeter. The third treatment was labeled as “mixed”, where the milkweeds were randomly dispersed around the garden with the other plants. Water, soil, nutrients, and weeds were all control factors, though predators were unable to be. The plants were each checked for pupae and larval spottings then left to continue pupating. 

How the gardens were set up.

At the end of the experiment, the scientists compiled the number of monarch pupas, eggs, and larva along with the type of treatment they were found on, and compared the data. They found that monarch butterflies were 2.5-4 times more likely to be drawn to the milkweed plants that were around the perimeter of the gardens rather than on the inside or mixed. They were also more drawn to the milkweeds that were separated from other plants, or that were not touching other plants. At the Monarch Waystations, the researchers found that the Monarchs were 5 x more likely to use a structured Waystation than an unstructured one. 

I think this paper is really interesting, as it applies directly to where I live, and also my area of interest. Monarch butterflies are an endangered species that have recently seen an 80% decrease in population in the last 25 years. This means that we must make efforts to attempt to support them on their migrational journey. Urban areas affect these populations of butterflies via light pollution, sometimes drawing them towards those urban areas, or causing them to migrate at night. If more Monarchs find themselves in urban areas, then urban areas need to be able to have plans and projects in place to assist this migration, even if it is simply through encouraging citizens to create and cultivate more Monarch-focused gardens that are planted efficiently. 

Baker, Adam M., and Daniel A. Potter. “Configuration and location of small urban gardens affect colonization by monarch butterflies.” Frontiers in Ecology and Evolution 7 (2019): 474.