Introduction
This summer, Plant Chicago worked with Lauren Lynch, an entomologist from the University of Illinois. Through specimen collection, Lauren studied how urbanization affects pollinator abundance and diversity, and the effects of pollinator conservation efforts for pollinators in cities, suburbs, and rural areas. To explore relationships between urbanization, pollinator abundance/ diversity, and the effects of flower-planting on pollinators, she monitored pollinators in thirty gardens and lawns in city centers, suburbs and smaller towns, and rural areas such as forests, prairies or agricultural landscapes in the Chicagoland area, one of them being Plant Chicago’s monarch waystation!
Pollinators and Conservation
Our ability to produce food relies heavily on the help of pollinators to fertilize flowers, allowing them to develop and ripen. While some crops (such as corn) can be wind pollinated, many of the fruits and vegetables that are particularly important sources of nutrition, such as squashes and melons, require insect pollination. With this in mind, patterns of decline in pollinator species are particularly alarming. According to the USDA’s National Agricultural Statistics Service Report, there were about 2.63 million honey bee colonies in the United States in 2018, less than half of the number that were present in 1947. Similarly, populations of Monarch butterflies have declined steadily over the past twenty years, and the diversity of native bee communities has decreased in many parts of the world.
Data collected by citizen scientists participating in the Western Monarch Thanksgiving Count show declining population trends.
Fortunately, there is a lot that we can do to protect pollinators and reverse these trends. The public response to declining pollinator populations has been tremendous. Individuals and organizations have mobilized to conserve pollinators by planting native flowers which provide food sources, creating nesting habitats, and participating in citizen science pollinator monitoring. According to the Million Pollinator Garden Challenge, over 940,000 pollinator gardens have been planted around the world.
Map from the Million Pollinator Garden Challenge – Pollinator gardens that have been registered in the Chicago area
Effect of Urbanization on Pollinator Conservation in Chicago
As you can see in the map above, many of these efforts to conserve pollinators are occurring in cities. Urbanization alters landscapes in a variety of ways that can change the quality of habitat available to pollinators and other wildlife. While some research, as you might expect, has found that urbanization causes declining pollinator abundance and diversity, other researchers have suggested that the prevalence of habitats such as home gardens in cities can actually provide highly valuable resources for pollinators (Hall et al 2017 describe cities as a “refuge” for pollinators).
When Lynch was selecting study sites, she began by choosing ten certified pollinator gardens. All ten of these gardens were registered through the Monarch Waystation program, which means they have been planted specifically to provide sources of nectar to pollinators. Plant Chicago’s monarch waystation was one of the pollinator gardens selected for this study for its composition of native flower species. Purple Coneflowers, Milkweed, and Bee Balm that bloom at different times throughout the Spring, Summer and Fall provide pollinators with a constant source of nectar and pollen. To compare the quality of habitat provided by these registered pollinator gardens to other types of habitat available in and around cities, Lynch paired each pollinator garden with an ornamental garden and lawn within one kilometer.
To understand the effects of urbanization on pollinator abundance and diversity, Lynch chose study sites on an urban-to-rural gradient. Lynch looked at a range of development intensity- including city centers, suburbs and smaller towns, and rural areas such as forests, prairies or agricultural landscapes. This gradient is important to acknowledge, as it is difficult to draw a concrete line between what is urban and what is rural.
Nine study sites were located in the city of Chicago, twelve sites were located in the suburbs of Chicago, and nine sites were located in smaller towns outside of the suburbs.
Their research team used two different methods to monitor pollinators. First, pollinators were captured using fluorescent bee bowls that are designed to attract pollinators. They are filled with soapy water to trap pollinators that land in them. While we always have our bee’s best interest in mind, it is nearly impossible to accurately identify bees without killing them. Lynch spoke with Jana Kinsman, beekeeper and owner of Bike-a-Bee, tenant of The Plant, to make sure her study wouldn’t interfere with business.
In addition to the bee collection, visual surveys were conducted. The team spent thirty minutes at a time walking through each garden and recording all pollinators that were observed landing on the reproductive parts of the flowers.
To limit independent variables, each study site was visited six times between May and August. All monitoring was conducted on days that were at least partially sunny with a temperature above 15.5 C and wind speeds below 20 km/hour.
What’s Next?
The data that was collected will be used to explore the effects of urbanization on pollinator abundance and diversity, and to evaluate the effects of planting pollinator gardens in and outside of Chicago. It’s possible they will find that fewer pollinators are present in Chicago than outside the city, or perhaps find that Chicago provides a home for as many or more pollinators as compared to rural areas. Additionally, it is possible that the effects of planting pollinator gardens are different inside and outside of the city. For example, if initial nectar availability is greater in rural areas, it may be that planting pollinator gardens has a greater impact on bees in urban areas.
Over the next months, Lynch will pin and identify the bees that were collected, as well as process and analyze data. The research team will be returning to The Plant next year and work with Plant Chicago to continue this research, so stay tuned!