Pollinator Update

In the spring of 2014, I published a three-part series on the importance of pollinators – bees, butterflies, wasps, hummingbirds and a variety of other insects – and highlighted the alarming rates of decline of their populations. (Here are links to those columns, Part I, Part II, and Part III.) I also described my own efforts to build/improve pollinator habitats and promised an update in the future. So, here it is.

I own two local parcels of land, a 0.15 acre plot at my house in northwestern Chapel Hill and a 16 acre tract two miles west of Carrboro which I operate as a hobby farm. Over the past several years, I have been making attempts to expand and improve pollinator habitats at both locations.

At my house, I have planted several perennial and annual flowerbeds to provide nectar as food. I have also cultivated plants such as milkweed, dill, and parsley that provide food for butterfly and moth caterpillars. These efforts have led to a small but discernible increase in the number of pollinator visits.

Results at my farm have been more noteworthy. Approximately 14 of the 16 acres of the land are forested and two small brooks that provide water for all sorts of wildlife border the property. In the cleared area, I have been growing vegetables, raising chickens, and planting large beds of native wildflowers. In addition, I maintain a three-acre meadow in an adjacent property by mowing it once a year in February. No pesticides of any kind are applied on the property. As a result of these efforts, my farm is alive with a loud and pleasing symphony from bees, butterflies and insects of all kinds. I have taken pictures of approximately 50 different species of insects and have been diligently trying to identify them using two field guides. The panel below shows four species that I have been able to identify. Starting in the upper left hand corner and continuing clockwise, these are the Common Buckeye, Eastern Bumblebee, Paper Wasp, and Great Spangled Fritillary.

The number insects that I have not been able to identify, far exceeds those that I have. The panel below shows four of my interesting visitors whose identities remain unknown. If you can identify any of these, please send me an email.

The fact that I have had difficulty identifying insects at my farm is not surprising. Across the globe, approximately 1,000,000 different species of insects have been identified, while the estimated total number of insect species is thought to to be around 30,000,000! While much of this insect diversity is concentrated in tropical latitudes, even here in the United States, at most, we have identified half of our resident insects.

I am hopeful that my efforts at both locations are having a positive impact on the local pollinator populations. But I often wonder if it is reasonable to believe that just one person could have a measurable impact? To evaluate this question, let’s consider the case of non-migratory butterflies. (Unlike the famous Monarch, most butterflies are not migratory.)

The map below shows a 20 square mile area of southeastern Orange County which includes the towns of Chapel Hill and Carrboro and some adjacent areas.

The locations of my farm and house are indicated with the F and H, respectively. In an acceptable habitat with flowers, places to hide, and a source of water, an individual butterfly might forage over an area of two square miles. To give you a sense size, the square drawn with the dashed purple lines on the map outlines an area of two square miles. Given the distances, we can see that the same butterfly is not likely to visit both my farm and my house. However, it is possible that both of my properties could be within the range of a breeding population of a group of butterflies.

Butterflies, like any other species, need a large gene pool to maintain a healthy population. In order to facilitate that, the foraging ranges of many individual butterflies need to overlap so that they can encounter one another while in an amorous mood. In addition, to the extent that favorable butterfly habitat is geographically fragmented, there need to be safe corridors between the sections to allow the butterflies to reach one another. Therefore, the range of a breeding population would consist of clumps of overlapping foraging ranges as well as adjacent clumps that are accessible via pollinator corridors.

If we look at the map again, we can safely assume that the areas which are shaded in green to indicate forests and fields, contain better butterfly habitats that that the unshaded areas within the towns. Given that my farm is ensconced in the green shaded zone, it is not particularly surprising that I have had success in attracting butterflies. If our collective goal is to create a pollinator friendly environment in the entire area on the map – and I sure hope that is our goal – then we need to focus on creating and maintaining safe transit corridors through the towns so that pollinator habitats are connected. For example, the railroad track indicated on the map is a great example of a place where a strip of meadow could be allowed to grow to create a pollinator highway.

At present, I would give Chapel Hill and Carrboro a grade of a B in terms of having pollinator friendly policies. We do a good job of identifying specific places where we intentionally support wildlife such as the Bolin Creek Trail or Merritt Mill Pasture. Where we falter is in excessive mowing.  A decision tree on whether or not to mow an area should work as follows. First we should determine if anyone every walks on the mown grass. If the answer to this question is “no”, then we need to ask if allowing the native plants to grow to a height of 3-4 feet would create any problems, such as obstructing the view of drivers at an intersection. If the answer to both of these questions is “no” then we should not mow the grass and more that once a year which is sufficient to keep trees from growing. This same analysis can be applied to your own lawn. Please consider if part of your lawn can be set aside as a natural area.

After thinking through issue, I do believe that it is quite likely that both of my properties are within the same breeding area for multiple species. Therefore, the enhancements I have made in habitat are quite likely to be contributing to a population increase and reinforcing each other in the process. However, my impact would be much greater if I could convince you to install pollinator habitat as well and if we could get our local governments to be more discriminating about mowing. Let’s give it a shot, the pollinators will thank us.

Jeff Danner talked about pollinators on WCHL Monday with Aaron Keck.

 

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