Pollinators are some of the world’s most important species, as they provide ecological services needed for agriculture, plant growth, and seed transportation. In urban areas, more and more pollinators are facing difficulties finding plants for pollination, especially native pollinators. This is due to degraded habitat, insecticides/pesticides, urban infrastructure, and human caused pollution. Riparian edges in and around urban areas are facing extreme degradation, as polluted runoff flows into these areas, people plant non-native or invasive species in these areas, or people use herbicides there. These areas are especially important for pollinators, whether they be migratory or native. This is especially important to me, as I work with bees, and am interested in working in the entomology field.

In a research article, Pollinators and urban riparian vegetation: important contributors to urban diversity conservation, from 2022, researchers did an observational study in which they recorded data comparing riparian vegetation and bee and butterfly abundance and richness. This study took place in Chongqing, China, along the Qingshui stream and the Phoenix Stream, (QS and PS from here on out). The study took place over a year, with observations occurring during each season, 11 times total. Plants were noted and identified on-site, with pollinators being collected in nets and taken back for proper identification. Using the Shannon-Wiener Index, richness index, and the Pielou Index, the researchers analyzed the richness and abundance of bees and butterflies along the two streams, and compared that data with the type of plants where they were found.

They found that the richness and abundance of native plants was very similar along both streams, but that composition of plants was very different. Unsurprisingly, higher bee and butterfly abundance and richness was observed during the spring and summer months, with it falling off a bit in the fall and winter months.  They found that bee and butterfly richness was significantly correlated with an abundance of native flowering vegetation. They also found that the habitat heterogeneity was more complex for butterflies than for bees. A section of QS had been destroyed due to herbicide use halfway through the experiment, and they observed an immediate decline in bee and butterfly populations along this section of the stream.

This paper shows the importance of preserving riparian buffers and edges in urban areas, but also preserving the integrity of these areas. Pollinators are extremely important to urban areas, as well as rural, and one way we can continue to promote them is through planting more native species. I think one way we could do this is by simply planting more native plants along sidewalks to increase pollinator presence, (at least in Raleigh), or by planting native pollinator plants in our gardens.

Zhang, X., Zhang, L., Wang, Y. et al. Pollinators and urban riparian vegetation: important contributors to urban diversity conservation. Environ Sci Eur 34, 78 (2022). https://doi.org/10.1186/s12302-022-00661-9

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.

In September of 2021, Merri K. Collins, Seth B. Magle, and Travis Gallo conducted a literature review of peer reviewed and scientific primary literature sources that had to do with urban wildlife from 2011-2020. In a previous literature review from 2012, Dr. Magle performed a similar review of primary literature articles from 1971-2010 also looking into urban wildlife. The original Magle paper found an increase in papers from 1971-2010 having to do with conservation, with the new paper finding an even larger increase.

This paper used literature criteria along with key words in order to find the sources. They searched on World of Science in the most high journals, along with the word urban, exurban, and periurban, but limited the search to just primary literature. They then organized their data into categories based of of areas of study, including animal behavior, conservation, ecology, general science, landscape ecology, and wildlife biology. They then broadened their search by using Google Scholar, and including the term wildlife with urban. They ended up adding spatial ecology and social science as two more areas of study in order to acomodate for the increase in articles written in those disciplines.

Once they collected all of the literature sources, they placed them into a table side by side with the table from the Magle paper from 2012. The data was the translated into a graph in order to show the extreme increase in urban wildlife papers since 2010, and can be found below.

This graph shows the uptick in publications from 1971-2020, but specifically from 2011-2020. In the original Magle paper, Magle has hypothesized this increase, and from the new paper, they expect an even greater increase.

The paper found the highest proportion of papers to be in the animal behavior discipline, followed by conservation, and then wildlife management. Mammal studies were the most common found, followed by bird studies. These scientists also made note of the fact that many of these articles came from North America, followed by Europe, with very little coming from Africa, South America, and lastly Asia.

After reading this literature review, I am hopeful that more and more research is being done in the urban wildlife field, especially in conservation. I do believe though that we need more research in areas that are underrepresented, along with more articles that are written in a more interdisciplinary way, as many of these issues can be tackled from different perspectives. I think it is interesting that animal behavior was the most common discipline articles were found in, as I would have originally thought it to be wildlife management.

I think that literature review papers can be very beneficial for public education, as they allow everyone to read, visualize, and understand trends in conservation and urbanization. Considering the majority of the population is projected to live in urban areas by 2050, it is important for people to learn the impact that this has on our natural lands and ecosystems. More wildlife biologists are focusing on urban wildlife research, which can only help us in the long run.

Merri K. Collins a, et al. “Global Trends in Urban Wildlife Ecology and Conservation.” Biological Conservation, Elsevier, 10 July 2021, www.sciencedirect.com/science/article/pii/S0006320721002883?casa_token=wYjg9uqo7sEAAAAA%3AXrA2S7D3aXz-rFSMBOzzI2JZXAsajrJFv8pk2uBBjEw-DX2CFM0gQHoYieIjrKYc_It00-ev-Voh.