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Native Bee Habitat Quality in Broomfield Colorado
December 2019
Becky Friend
Butterfly Pavillion Project
Abstract
Native bees in Colorado need a set of habitat qualities to survive. Firstly, they need ample resources to forage from. Secondly, they need sun exposure that allows for adequate plant growth and warm, dry places for nesting. Thirdly, native plants provide a more efficient resource of nutrition for native bees. Lastly, open ground with foliage allows nonnative bees to burrow and breed. The Urban Prairies Project (UPP) conducts land restoration in the open spaces of Broomfield, Colorado to restore native habitat. In this atlas, two open spaces, Plaster Reservoir and a portion of Big Dry Creek, are compared against each other. These two open spaces have differing qualities that can support or hinder native bee populations. Plaster Reservoir has more native plants, breeding areas, foraging for the native bees to survive. Big Dry Creek, however, is full of noxious weeds and has barren spots with no vegetation. We can conclude that land restoration is needed on Big Dry Creek and Plaster Reservoir will need to continue restoration to maintain and improve current conditions.
Introduction
There are around 20,000 bee species in the entire world. 4,000 of those native bees find homes in the United States. Colorado is home to 946 species, making it the 5th most bee diverse state in the United States. Even though honeybees are important pollinators in agriculture, native pollinators are more important for our native ecosystems. Native bees have co-evolved with the native flowering plants in Colorado. This has made them more efficient and effective pollinators of native flowering plants. Colorado native bee species can take many forms. The species vary in behavior, color, size, hairiness, and shape. Most of Colorado native bees are not social. 70% of native bees are solitary, meaning they create their own nest and provision their own food. The other 30% of native bees are either social, meaning the bees conjugate in a hive or nest. The vast majority of Colorado native bees nest in the ground and in wood. Therefore, the bees need open dirt space with some fallen foliage to build their nests and to breed. Native bees also need the right amount of sun exposure and water to help the flowering plants they forage upon survive.
The Urban Prairies Project (UPP) is working towards improving the ecological health of open spaces in the City and County of Broomfield, the City of Westminster and beyond. Ecological health is improved through land restoration of native habitat. Such restoration takes the form of weed management, revegetation, and habitat monitoring. The restoration of these open space provides a variety of benefits to the community. However, pertaining to this atlas, land restoration acts to improve native bee habitat. Therefore, two open spaces were picked from the UPP and compared for their native bee habitat. The two spaces were Plaster Reservoir and a portion of Big Dry Creek. It is important to note that this is a pilot study to learn the mapping skills associated with data collecting and analysis. More open spaces in Broomfield would need to be tested to have a robust comparison.
Methods
Plaster Reservior
Big Dry Creek
The two open spaces were picked because of their convenient location, workable acreage, and their contrasting characteristics. The first step to mapping and gathering data for this atlas was to determine the boundaries of the open spaces. The boundaries were defined by the head horticulturalist and manager of UPP. The boundaries were then digitized into ArcGIS Pro 2.4. The two open spaces were then broken up into two different habitats. The first habitat was Upland. Upland habitat is known for its low-lying shrubs and grasses. This type of habitat is typically very dry. The other habitat was riparian. Riparian is the habitat that borders water and upland. It is usually full of lush greenery, cattails, and trees. Riparian habitat was determined using a buffer and predetermined buffer range. Larger bodies of water needed larger buffers of 15 meters whereas small streams or rivers needed a smaller buffer of 3 meters. The upland was then determined by the boundary and erasing the riparian habitat out of the upland area.
To gather points an attribute table and layer were created. The attribute table had values that could be filled in for open space name, habitat, foraging percent, breeding percent, sun exposure present, and nonnative plants percent. A random dot tool was then used to randomly pick data locations within the boundaries. The number of dots in each open space was determined by the acreage. For every acre, 3 dots were plotted. All the layers were exported onto ArcGIS Online. Once online, the layers could be reached using the Collector app. The Collector app allows people to gather data in the field and then the app automatically turns that data into points on a map based off the GPS location. In the field, a 10x10 quadrant was used to count the nonnative plants, breeding habitat, and foraging habitat. That number was then inputted as a percent into the Collector app. The layers were then exported back into ArcGIS Pro 2.4 where the data could be used to create the following maps.
DATA COLLECTION
Gathering data for my project at Plaster Reservoir
Results
Sun Exposure
Sun exposure is important for native bees so their foraging plants can thrive. Typically, Coloradoans see 300 days of sunshine a year. This provides the energy for plants, including nonnative and native plants, to thrive and reproduce. For these maps, a data collector stood at the spot which was randomly generated. Based on the sun exposure and nearby tall objects, the data collector determine how much of that spot was exposed to sun. If the map reads 60%, then 60% of that area was exposed and 40% of that area was in shadow.
For the most part, both the open spaces had good light exposure. The areas where they varied were typically in areas with trees. The trees occurred most frequently along the riparian areas where there was more water for tall plants to grow. Some trees also grew closely to golf courses and schools. This could be attributed the irrigation runoff giving these trees water. In the areas along the riparian that did not have trees for sun cover, the area was blanketed in cattails. Though cattails are not invasive, they do not provide any useful resource to native bees.
Foraging Habitat
Native bees need flowering plants to gather pollen for survival. Not only does this act as their food source, but they are also helping to cross pollinate plants. Such native plants that are good for this are Rabbitbrush, Cottonwoods, and Sunflowers. For the maps, a quadrant was placed. If there was a flowering plant within the quadrant square it was counted as 1. Therefore, a quadrant with 80% had flowering plants in 80 of the squares.
Overall, Plaster Reservoir had more foraging. There were more plants that were flowering and there were more native plants. When Big Dry Creek did have foraging, it was mostly from invasive weeds such as Bind Weed. However, there was a patch of Rabbitbrush along a slope just west of the river where the majority of the foraging habitat was found on Big Dry Creek. It seemed very localized to that area. I predict the City of Broomfield has done some land restoration along this slope to avoid erosion of the slope.
Breeding Habitat
Most native bees are solitary and burrow in the ground. They create holes where they rear their young. To create these holes, the habitat must have loose foliage and exposed soil. Within the quadrant, exposed soil with foliage was counted. For example, 10% means 10 squares in the quadrant had breeding habitat.
Plaster Reservoir had less breeding habitat than Big Dry Creek. However, plaster has more water going through it, increasing density of plants which caused there to be less open ground. Big Dry Creek had a lot of open space for breeding because it was very dry and a prairie dog colony clipped the vegetation down. There were not many lush, green plants, therefore increasing the open ground. Though this may help with breeding, native bees need vegetation to forage.
Nonnative Species
When nonnative plants enters a habitat, it can be detrimental to the native organisms. The nonnative plants take over areas and don’t give native foraging plants a place to grow. The nonnative plants are difficult to kill and spread quickly. However, native bees have a dual relationship with invasive plants. Some invasive plants provide foraging if the plants bloom. For example, Bind weed blooms and provides foraging, but is considered an invasive weed. For these maps, the number of invasive plants was counted within the quadrants. 100% means the entire quadrant contained nonnative plants.
Big Dry Creek had significantly more invasive plants than Plaster Reservoir. The middle section of Big Dry Creek was a patch of nonnative grasses. There was also a patch of Russian Olives on the North Eastern section of the open space. For both the open spaces we can see that nonnative plants occurred frequently next to neighborhoods, schools, and golf courses. I predict that the ornamental grasses used in these areas spread into the open space. Despite Big Dry Creek having a lot of invasive species, it provided good foraging. Restoration is needed in the Big Dry Creek Open space to encourage native foraging plants to grow.
Criteria Comparison
These maps are a representation of all the criteria mentioned above combined into one map. The criteria were symbolized based on their "goodness" and "badness" for native pollinators in Broomfield. For these maps, the good habitat qualities are presented with darker colors. Conversely, less advantaged criteria are white. The symbols are all represented with the same color scheme and transparency. The transparency allows for colors to stack on each other. Therefore, the darker the circle, the better the native been habitat for that collection point. Native species were inversed because the more Nonnative species that exist, the worse the habitat will be.
As can be seen, Dry Creek had significantly lighter circles. This mostly due to the dry conditions and the cover of invasive grass. Plaster had far more areas with darker circles indicating that it is a better habitat for the native bees. We can conclude this occurs because Plaster has more water with native plants from the restoration done by UPP. Further, we can see that there are lighter circles, or bad habitat, next to the golf course, lawns, and schools. This could be attributed to the ornamental grasses moving into the open spaces and over-irrigation causing nonnative weed plant growth spurts.
Discussion
Both the open spaces provide an interesting look into native bee habitat. Big Dry Creek had far fewer native plants but had a lot of open ground for breeding and good foraging. Plaster, on the other hand, had more native plants and more foraging but was lacking a bit in open spaces for breeding. Overall, I would rate Plaster as a better habitat. When walking through both areas, Plaster had lush green resources for the native bees to harvest. I attribute this to the land restoration that has already taken place in Plaster Reservoir and the amount of water running through the space. Big Dry creek seemed more of a monocrop of an invasive grass and had prairie dogs clipping down vegetation that could be used for pollinators. From this study, we can see that Big Dry Creek needs restoration work done. Russian Olives need to be removed and native plants need to be integrated with the grasses. Plaster also could benefit from restoration to maintain the good habitat that is already there and to address some areas along the golf course in the northern boarder.
When looking at the upland areas verses the riparian habitat some significant observations can be made. Upland was much drier with low lying shrubs while the riparian provided moisture for tall plants and trees to grow. For native bees to be successful, they need the moisture of the riparian to let large foraging plants to grow and the dryness of the upland to have breeding space. Both areas work hand in hand to produce the native habitat for bees. Too much influence from either habitat would decrease native bee population. For example, if the riparian flooded over into the upland, the bees would lose their breeding areas and their foraging in that area would be destroyed. Conversely, having too much upland conditions would make it too dry to plants to grow and native bees could not forage.
Colorado Native Bees
Next Steps and Conclusion
As discussed, it will be of upmost importance to begin and or continue land restoration of these open spaces. Below, I have provided a restoration plan based off the removal of noxious weeds and the revegetation of native species as outlined by the Butterfly Pavilion…
In the future, a study should be conducted during the warmer months when flowers are blooming. Since this study was conducted after a frost, it was difficult to tell the difference between invasive and noninvasive species. The bright colors of the blooms would help data collectors get more accurate data. Also, it would be interesting to see how the season affects native bee habitat. For example, would early fall provide the best foraging, or would early spring be better? More research is still needed on how a changing climate will alter bee habitat in Colorado and what communities can do to protect their native bees.
Big Dry Creek
1. Erosion management/ Soil amendment
Erosion Management may be needed if the areas clipped by prairie dogs begin to erode.
2. Need: Weed management
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Cheat Grass – approximately 90% of land area
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Action item/ responsibility/ timeline
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Harvest the seeds of cheatgrass before they germinate
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This would take place over many years and would happen every season
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Evaluation - This would be a time-sensitive operation and labor-intensive. However, it would avoid the use of harsher methods such as herbicides.
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Russian Olive – approximately 30% of land area
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Action item/ responsibility/ timeline
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The trees will have to be manually removed. There is a large grove of them. This process will take a lot of manpower and months to complete since there are many large patches of Russian Olives.
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Evaluation - It may be difficult to find volunteers interested in doing this type of work and it may be too expensive to use a private company to remove the trees. On the other hand, an organization ROT (Russian Olive Team) are volunteers trained in taking down Russain Olive. ROT will be a good resource to get rid of Russian Olives and help train other volunteers.
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Bindweed – approximately15 %of land area
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Action item/ responsibility/ timeline
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Spot weed as needed. Especially before they go to seed. Replace with a native plants
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This can be done every season and it is relatively easy to work. Results may be seen within one season.
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Evaluation - Almost any volunteer would be able to conduct this activity therefore, it would have a high success rate.
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3. Revegetation
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Revegetation species
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Milk Weed
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Willow
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Rabbit Brush
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Revegetation plan
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Action item/ responsibility/ timeline
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Collect seeds of these species from other areas and plant them in areas that need the native species.
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Evaluation - Relatively low cost to the Butterfly Pavillion because no seeds have to be bought.
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4. Other tasks
Manage the prairie dog population to ensure they have resources and to make sure they are not doing too much damage.
Plaster Reservior
1. Erosion management/ Soil amendment
The soil in this area seemed very rich and lush. This could be attributed to the presence of water from the many creeks that run from the reservoir.
2. Need: Weed management
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Curly Dock – approximately 10% of land area
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Action item/ responsibility/ timeline
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Deadhead the stalks when seeds emerge in the fall and pull the plant out during the spring and summer. This can be done almost all year around. As long as seeds do not spread, this could be an effective management style and effects could be seen right away.
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Evaluation -
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This is a low cost and easy task. The only issue would be walking the areas to find the docks.
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Ornamental Grass – approximately 40% of land area
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This area is rimmed with ornamental grass from the neighborhoods and golf courses. The get rid of this, the UPP would have to work with the community to remove the grasses. For example, the gold course would have to edge their grass around the open space and the grass around the neighborhood could be made into wildflowers.
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This process would take a long time because there are multiple stakeholders involved that may not want to spend the extra resources to fix the area.
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Evaluation - This may be a difficult solution because the golf course most likely doesn’t care about the open space next to them. They are probably only worried about profit.
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3. Revegetation
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Revegetation species (see below)
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Milk Weed
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Rabbit Brush
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Willow
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Cottonwood
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Revegetation plan
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Plant seeds and sapling in areas that have recently been weeded. Maintain care of the plants to ensure their success.
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Evaluation - This process is similar to other restoration plans done with the UPP. It has a high chance of success.
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4. Other tasks
Engage with the community to better the open spaces. The effects of restoration will be more long-lasting if communities understand the importance of maintaining the native ecosystem. Community outreach could take place through local schools and colleges. Classes can be offered to those interested and certifications can be awarded to those who have completed enough training. Further, the UPP and the Butterfly Pavillion can table at events such as the West Fest and the 4th of July celebration to spread the word about land restoration. Finally, holding a strong social media presence will help people stay informed and promote exposure to the program.
Resources
Arathi, H.S, et al. “Attracting Native Bees to Your Landscape - 5.615.” Extension, Colorado State University , Nov. 17AD, https://extension.colostate.edu/topic-areas/insects/attracting-native-bees-landscape-5-615/.
Doran, Alicia, et al. Noxious Weeds of Colorado. Colorado Weed Management Association, 2018.
“Intro To Native Bees.” Bees Needs: Intro To Native Bees, University of Colorado Museum of Natural History, https://beesneeds.colorado.edu/introtonativebees.html.
“Invasive Species.” Colorado Natural Heritage Program, Colorado State University , https://cnhp.colostate.edu/ourwork/invasive-species/.
Russell, Howard. “Solitary Bees in Yards a Temporary Nuisance.” MSU Extension, Michigan State University, 2 Oct. 2018, https://www.canr.msu.edu/news/solitary_bees_in_yards.
Wright, Abigail, and Crystal L Boyd. “The Bumble Bees of Colorado A Pictorial Identification and Information Guide.” Feb. 2017, https://www.colorado.edu/cumuseum/sites/default/files/attached-files/thebumblebeesofcolorado-2017.pdf.
Acknowledgments
Thank you to Ashley White and Amy Yarger at the Butterfly Pavillion for mentoring me throughout this project. They provided me with endless knowledge about Colorado's open spaces and restoration.
Thank you to the University of Colorado Denver's Fast lab for helping me troubleshoot issues on ArcGIS and for training me on how to use new software. This project would not be possible without the help of Justin Culman and Michael Hinke.
Finally, a big thank you to my lab assistant in training, Trevor Smith.
Lab Assistant in Training
Trevor and I just got done tromping through some foliage. We got a little dusty to say the least.