In this post, I cover the 2009 paper, “Impact of native plants on bird and butterfly biodiversity in suburban landscapes,” by Karin Burghardt, et al.[i]
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This study was published shortly after the first edition of Doug Tallamy’s book, Bringing Nature Home: How Native Plants Sustain Wildlife in Our Gardens.[ii] After decades of studying host plant records of butterfly and moth species, Tallamy was convinced that native plants were critically important to wildlife conservation. About half of all insects are herbivores, and about 70 percent of all herbivores are specialists that are only capable of feeding on a narrow range of plants (see Schoonhoven et al. 2005, Chapter 2, pages 5-9). Specialist insects have developed, over time, the ability to feed on plants that have physical or chemical deterrents that keep generalist insects at bay. Although specialist insects can feed on plants that can be toxic to other insects, they can’t easily switch to feed on novel, non-native plants.
Burghardt and Tallamy’s Study of Native Plants and Caterpillars
Tallamy was Karin Burghardt’s master’s degree advisor and one of her co-authors on the 2009 paper. In their study, they selected six pairs of suburban gardens in central Pennsylvania. Gardens were paired by size and proximity. One garden in each pair featured the conventional landscaping for this region: large lawns, Asian shrubs, Asian understory trees, and native canopy trees. The other garden was landscaped with native ornamentals at each vegetative layer: grasses, shrubs, understory trees, and canopy trees.
They counted the number of caterpillars at 12 points within each garden. Since caterpillars are herbivores, and most insect herbivores are specialists that do best on native plants, they hypothesized that they would find more caterpillars in the native plant gardens. Indeed, this is what they found. Caterpillar abundance was four times greater, and caterpillar species diversity was three times greater, in the native gardens versus the conventional gardens. In addition, Burghardt found that native plant gardens harbored more birds. In fact, native plant gardens had 55 percent more birds and 73 percent more bird species, compared to conventional gardens!
This study demonstrated that gardeners’ choices matter and can clearly influence ecological food chains. Food chains are organized into what are known as trophic levels. Organisms on the same trophic level share the same ecological function and nutritional distance from the sun. Photosynthetic plants are on the first trophic level. Herbivores, or organisms that eat plants, are on the second trophic level. Organisms that eat herbivores, such as birds, are on the third trophic level.
Burghardt and Tallamy demonstrated that what you decide to plant in your garden not only determines the structure of the first trophic level but can also cascade up to affect the second and third trophic levels. As an entomologist, I was not surprised that gardeners’ plant selections could influence the second trophic level. However, I was blown away that these decisions could cascade up to strongly influence the third trophic level.
Garden Ecology Lab Studies of Native Plants and Bees
In the Oregon State University Garden Ecology Lab, we study relationships between native garden plants and native bees. To be honest, I did not expect that native bees would prefer native plants. Whereas the leaves and other vegetative parts of a plant include an array of chemical and physical defenses to protect the plant from insect herbivores, flowers have few such defenses. In fact, flowers function to attract pollinators to a plant.
Thus I was somewhat surprised when Ph.D. student, Aaron Anderson, found that most of the native plants in his study attracted more native bees and more species of native bees than his non-native comparison plants. For example, non-native lavender ‘Grosso’ attracted a large number of bees, but most of these bees were non-native honey bees. By and large, the native plants were better for bee abundance and bee diversity, compared to the non-native comparison plants. In particular, Globe Gilia, Farewell to Spring, Oregon Sunshine, Douglas Aster, and California Poppy were all particularly attractive to native, wild bees in Aaron’s study.
Why might native bees prefer native plants, when flowers don’t have the same chemical and physical deterrents that herbivores must contend with? One hypothesis is that the nectar and pollen in native plants might provide better nutrition to native bees. Another hypothesis is that pollinators are keenly tied into the visual display of native plants. Flower color, size, shape, and ultraviolet markings are all important signals that flowers use to attract the attention of various pollinators. If there are changes in any aspect of this visual display, pollinators may no longer recognize a flowering plant as a good source of pollen or nectar.
Another OSU Ph.D. student, Jen Hayes, is trying to understand why native plants seem to be preferred by native pollinators. As part of her Ph.D. work in the Garden Ecology Lab, Jen is collaborating with an OSU photography student, Svea Bruslind. Svea uses different filters to take photographs of native plants and native cultivars in visible light, ultraviolet light, and in “bee vision” light. We are just getting started on this study, but look forward to reporting our findings in the near future.
[i]Burghardt et al. 2009. Impact of native plants on bird and butterfly biodiversity in suburban landscapes. Conservation Biology 23:219–224.
[ii] Updated and expanded version published as Bringing Nature Home: How You Can Sustain Wildlife with Natives Plants.
This past year presented challenge and change to the Garden Ecology Lab. COVID locked us out of the lab and out of the field for a period of time. We said goodbye to two lab members (Angelee graduated! Cliff decided to move on from graduate school), and said hello to new lab mates (Cara took over Cliff’s project; Gwynne started her post-doc; Tyler, Jay, and Max all joined the lab as undergraduate researchers and research assistants). In addition to COVID and personnel changes, I had orthopedic surgery that took me away from work for a little under a month.
But somehow, despite the challenges and changes, we managed to make progress on several research projects. Below, I present a partial reporting of the Garden Ecology Lab year in review for 2020. Besides each project heading is the name of the project lead(s).
1) Garden Bees of Portland (Gail & Isabella):Jason Gibbs’ group from the University of Manitoba provided final determinations for a particularly difficult group of bees to identify: the Lasioglossum sweat bees. In addition, Lincoln (Linc) Best provided determinations for garden bees collected in 2019. Isabella is entering in some of our last remaining specimens, and I am working through the database of over 2,700 collected specimens to ‘clean’ the data and double check data entry against specimens in hand. There are a few specimens that need to be re-examined by Linc, now that we have determinations from the University of Manitoba, the American Museum of Natural History (Sarah Kornbluth), and a graduate of Jim River’s lab (Gabe Foote).
Altogether, we collected between 76 and 84 species of bee across a combined acreage of 13.2 acres (sum total acreage of 25 gardens). The low end estimate conservatively assumes that each unique morphospecies (i.e. Sphecodes sp. 1 and Sphecodes sp. 2) are a single species, whereas the high end estimate assumes that each is a unique species. A few noteworthy specimens:
We collected one specimen of Pseudoanthidum nanum, which is a non-native species to our area, which seems to be establishing and spreading in Portland. Stefanie Steele from Portland State University is writing a note on this apparent introduction, and is using data associated with our single specimen in her paper.
We collected one specimen of Lasioglossum nr. cordleyi which might or might not be a new species. The notation nr. cordleyi means that this specimen looks similar to L. cordleyi, but that the morphology of this specimen is different enough than the normal ‘type’ for this species, that it catches your attention. Jason Gibbs’ group is retaining that specimen. Further study will be needed to determine if it is indeed a new species, or not.
Some of the species we collected (as well as their ecological characteristics) suggest that gardens might be healthy habitat for bees. For example, we collected 72 specimens of Panurginus atriceps, which is a ground-nesting, spring-flying bee. Previous studies of garden bee fauna found ground-nesting and spring-flying bees to be relatively rare. We found them to be surprisingly (but relatively) common in our collections. We also collected seven putative species and 23 specimens of Sphecodes bees. This type of bee is a social parasite that does not collect nectar or pollen or construct a nest for their brood. Instead, they take advantage of the hard work of other bee species, by laying their eggs in the nest of another female. Parasitic bees are often used as bioindicators of habitat health. They would not be present on a site, unless the site also supported their obligate hosts.
We collected two species of bee that are listed on the IUCN red list for threatened and endangered species: Bombus fervidus (18 specimens) and Bombus caliginosus (10 specimens). I am not yet sure if their presence in urban gardens suggests that these species are recovering, that these species might be urban-associates that would be expected to thrive in urban gardens, and/or if gardens might represent particularly good habitat for these species.
In 2021, I *hope* that I can complete gathering data for this study, so that I can begin to analyze data and write. I hope to make it out to every garden, one last time, to finalize garden maps that will be used to calculate the area allotted to ornamental plants, edible plants, hardscape, and unmanaged areas. Aaron has already mapped out the landscape surrounding each garden at radii of 500 and 1000 meters. Together, these data will be used to understand whether/how garden composition and the surrounding landscape interact to influence bee species richness.
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Gail collecting bees off of flowers, using an insect aspirator (left). A wildflower meadow in one of our largest gardens (center). Some of the over 2,000 specimens we collected, and Isabella pinned and labelled.
2) Native Plants and Pollinators (Aaron Anderson): In February, Aaron successfully defended his dissertation proposal and passed his oral examination, and thus advanced to Ph.D. candidacy!! Since that time, he has been busy sorting, identifying, and counting three years’ of insect samples from his 140 study plots, representing five replicates plots of 23 native plants, four ornamental plants, and a control ~ a task that he finished two weeks ago! His bees have been identified to species by Linc. Aaron has identified the thousands of other insects in his samples to the taxonomic level of family. He is working through analysis of his massive data set, and is simultaneously working on two manuscripts: one focused on just the bees and the other covering all other insects. We plan to turn the key points of these two chapters into an infographic that can be used by gardeners and green industry professionals, to select native plants that support an abundant and diverse assemblage of beneficial insects.
Aaron recently submitted the first paper from his dissertation for publication consideration, to the journal HortTechnology ~ and it was accepted, pending revisions! This paper reports on his survey of gardeners’ impressions of the aesthetic value of his study plants, and includes five specific recommendations for native wildflowers that Pacific Northwest nurseries might consider growing and marketing as pollinator plants (e.g. Gilia capitata, Clarkia amoena, Eschscholzia californica, Madia elegans, and Sidalcea asprella virgata). These plants all fell within the ‘sweet spot’ of being attractive to both pollinators and to gardeners.
Aaron’s plots at the NWREC station remain in place. Although we are through collecting data for Aaron’s study, I am applying for grant funding to study how plant traits ~ both the reward that plants offer pollinators and the displays that they use to attract pollinators ~ change with plant breeding for specific aesthetic traits, and whether/how these changes affect pollinator visitation. We also hope to study how highly attractive pollinator plants function in mixed plantings and in garden settings.
Aaron and Lucas measuring plots in year one (left); Douglas Aster, one of Aaron’s most attractive plants for bees (center); Oregon sunshine was less attractive to bees than we had expected.
3) Bees on Native Plants and Native Cultivars (Jen Hayes):
Jen successfully completed her first field season of research, which is a monumental accomplishment during this time of COVID restrictions on our work. In early 2020, Jen finalized her list of study plants, which included one native species and 1-2 hybrids or native cultivars. This, in and of itself, was a huge accomplishment. Although we started with a much broader list of potential study plants, so many native plants did not have native cultivars or appropriate hybrids available for sale.
Jen’s study plants, which include one native (top photo in each group) and 1-2 native cultivars or native hybrids.
Once Jen and her crew put the plants in the ground, a new set of challenges emerged. For example the native yarrow emerged with pink flowers, which was a clear signal that these plants were not true natives. In addition, the Sidalcea cultivars that Jen and her crew planted came up looking different than the Sidalcea native. This sent Jen on a journey to the OSU Herbarium, where she learned that the Willamette Valley’s native Sidalcea malviflora has been reclassified as Sidalcea asprella, and that the cultivars we purchased were hybrids of Sidalcea malviflora (native to SW Oregon and California). This all suggests a need to work with local nurseries and/or growers of native plants, to see whether or not there needs to be or can be standards for sale of native plants. Should native species and native cultivars be verified or share provenance? Should gardeners be asking for this information? I don’t know, but I think that they’re important questions to consider.
With one field season’s worth of data in hand, the native cultivars were more attractive to all bees (with overall patterns being driven by the abundance of the European honey bee) for all floral sets, except California poppy. When we excluded honey bees from the analysis, to look at (mostly) native bees, no clear pattern of visitation on native plants versus native cultivars emerged. Native California poppy was most attractive to native bees. But, native cultivars of Sidalcea were more attractive to native bees (keeping in mind that in 2020, our native cultivars were not cultivars of our regionally appropriate native plant). For all other plants, there was no difference. We look forward to collecting additional data in 2021 and 2022, to see if the lack of difference in bee visits to native plants versus native cultivars holds up. Particularly for the perennials, we are finding that bee visits change so much from year to year, as the plant becomes established.
Jen, pre-COVID times, discussing her research at the Urban Ecology Research Consortium conference (left). On every study plant, Jen takes data on corolla width and depth, as well as nectar tube length (center). Jen’s study site, with California poppy in the foreground, and a cultivar of California poppy towards the back (right).
4) Garden Microbes in Soil and on Skin (Dr. Gwynne Mhuireach): Dr. Mhuireach successfully recruited 40 gardeners to participate in this study: 20 from western Oregon and 20 from the high desert. She has received and processed all soil samples and all skin swab samples for PCR (genotyping), which will be used to infer the diversity and identity of the soil microbial community in garden soils and on gardeners’ skin. She has also received survey responses from all study participants, so that she can characterize gardeners’ crop types, time in the garden, and gardening practices (e.g. organic, conventional, or mixed).
Dr. Mhuireach then sent me the soil samples, so that I could process them for submission to OSU’s Soil Health Lab. The Soil Health Lab is currently performing the chemical and physical analyses on each soil sample, so that we can determine if there is any relationship between soil characteristics, gardening region (e.g. western Oregon or high desert), crop choices, management practices, and the microbes that can be found in garden soils and/or on gardeners’ skin. Gwynne just received the first data back from the PCR analyses ~ and we can’t wait to share some of the intriguing findings with you, after we’ve had some time to process and digest the data!
Because of COVID-19 lab closures, we are a bit behind where we had hoped to be at this point. We anticipate receiving all data from each service lab by the end of January or in early February. You can read more about Gwynne’s project, here.
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Beyond these four studies, Tyler started his BioResource Research project (costs and yield of container grown and intercropped tomotoes), and Isabella worked on her thesis (parasitoids in Portland area gardens). We also collaborated with OSU Computer Science students to turn a database of first frost / last freeze dates that Angelee compiled, into a web-based app (the app is still in beta-testing, but we hope to release it, soon!). I will detail those studies, in another post. But for now, I’m getting excited for the smell of carnitas that is filling the house, and that will go on top of the New Years’ nachos that will help us ring in 2021! I hope that you all have a very Happy New Year, and that 2021 brings health, and happiness, and joy to all.
I distinctly remember the day that I decided I wanted to study wild bees. I was sitting in a darkened auditorium at the American Museum of Natural History in New York City, listening to Claire Kremen deliver the plenary address in a symposium focused on invertebrate conservation.
In her address, Dr. Kremen shared the results of her research on watermelon farms in California’s Central Valley. Like all cucurbits, watermelon requires insect pollination to set fruit. Watermelon, in particular, has a high pollination requirement: it takes at least eight bee visits to deposit the 500-1,000 viable pollen grains needed to set harvestable fruit in seeded watermelons. Seedless watermelons require between 16 and 24 visits by a bee in order to set fruit. Most growers meet the high pollination requirement of melons by renting and placing honey bee hives in fields. Dr. Kremen’s research suggested that a different approach might be possible.
Honey bees are important agricultural pollinators, in large part because they can be moved en mass and placed into farm fields at the exact moment that pollination services are needed.Photo by Isabella Messer.
Dr. Kremen and her colleagues studied three types of watermelon fields that varied in their pest management practices (organic or conventional) and their proximity (near or far) to native habitat in the foothills of the California coast range. These fields were: organic near, organic far, and conventional far. Watermelon fields that used conventional pest management practices and that were located near the foothills were not included in this study because this type of farm did not exist in the region. The team determined the number of pollen grains that different bee species deposited on watermelon, by presenting different bees with a single watermelon blossom that had yet to receive any insect visits. After a blossom was visited by a single bee, the flower was bagged and tagged accordingly, and the number of pollen grains deposited on the stigma by that single bee was counted in the lab. They repeated this process for 13 different bee species.
Next, the team sat in watermelon fields and observed what types of bees visited watermelon blossoms, in different types of farm fields. Watermelon flowers are only receptive to pollination visits for a single day. They recorded the sex and species of each bee visitor to the blossoms. Based upon these species specific counts, combined with the pollen deposition data (above), they were able to assess how much each particular bee species contributed to the production of harvest-ready watermelon.
Dr. Kremen found that pollination surpassed 1,000 pollen grains needed to set harvestable fruit per flower in the organic near fields but not in the organic far or the conventional far field (Fig 1, part A). Furthermore, she found that this outcome could be tied to the greater diversity and abundance of bees in organic near fields, compared to the other two types of fields (Fig 1, part B).
Figure 1. The number of pollen grains deposited on watermelon stigmas (A), and the diversity (orange circles) and abundance (yellow stars) of bees (B) on farms that were classified as organic near (ON), organic far (OF), and conventional far (CF). The number of pollen grains required to set marketable fruit (1000) is noted via a red threshold line in A. (modified from Kremen et al. 2002).
Dr. Kremen also found that, even though no single species of wild bee was as effective as managed honey bees, the collective group of wild bees surpassed the effectiveness of honey bees in organic near fields (Figure 2). Interestingly, honey bees were most effective as crop pollinators in the conventional far fields and least effective as crop pollinators in the organic near fields. This may be because few other flowers were in bloom in the conventional far fields, so that honey bees concentrated their attention on the crop at hand. In the organic near fields, a greater diversity of flowering plants likely competed for the pollination services of honey bees.
Figure 2. The cumulative contribution of native bees, compared to the contribution of honey bees to the pollination requirement of watermelons on organic near (orange circles), organic far (navy squares), and conventional far (yellow stars) farms (modified from Kremen et al. 2002).
Wild bees were able to fully satisfy the pollination requirements of a crop with an extremely high pollination requirement because broad spectrum insecticides were not used, and the foothills provided year-round and protected habitat for the bees. This story blew my mind!
Prior to that conference, I had never given wild bees much thought. They’re mostly solitary nesters, with small bodies, that only forage for a few days to a few weeks. They tend to be inefficient foragers, particularly when compared to the juggernaut of a honey bee hive. Whereas wild bees are akin to a single vendor on Etsy, honey bees seemed the unbeatable Amazon!
Dr. Kremen’s work showed the potential value that wild bees have to agriculture. And her work was published just prior to the global onset of colony collapse disorder in honey bees in 2006. It set off a worldwide discussion about what to do about honey bee losses. Should scientists put time and effort into saving a single, non-native species (the honey bee), or should we work to conserve or build habitat around farm fields while also reducing insecticide use?
I was incredibly hopeful that the simultaneous threat to honey bees and promise of wild bees might promote heavier investments in agroecology, including the conservation of bee-friendly habitat around farms. During this time period, I was also in the early stages of documenting wild bee biodiversity in community and residential gardens, and I was surprised that abundance and diversity of garden bees was much higher than I had anticipated.
Back in 2004, I started to see gardens, and the abundance and diversity of wild bees that they host, as a potential solution to the problem of colony collapse disorder. Although I continue to be fascinated by the potential role of home and community gardens as a safe haven for bees from agricultural stresses, the urgency of this question has faded. Colony collapse disorder does not currently plague honey bees, due in large part to federal investments in studying, understanding, and mediating the factors that contribute to failing hives. With honey bees doing much better, attention has somewhat faded on the potential role of wild bees as crop pollinators. Still, work in this area continues and may rise to renewed importance, should colony collapse disorder again present a major challenge to United States agriculture.
Wild bees, including this leaf-cutter bee in the genus Stelis are also potentially important crop pollinators. However, many farm practices, such as regular insecticide sprays and mono-cultural cropping systems, make farms inhospitable to wild bees. Photo by Isabella Messer.
Kremen, Williams, Thorp. 2002. Crop pollination from native bees at risk from agricultural intensification. Proc. Natl. Acad. Sci. 99: 16812-26816. DOI: 10.1073/pnas.262413599.
Our colleague, Brooke Edmunds, was kind enough to shoot and edit this short video on two of our current lab projects: Jen Hayes’ study of native plants and nativars and Tyler Spofford’s study of the economic costs and benefits of growing vegetables in bucket gardens.
As we near the end of our 2020 field season, stay tuned for research updates.
This is the second is a series of articles that I am writing for the Hardy Plant Society of Oregon Quarterly Magazine. I extend my thanks to the HPSO editorial team for improvements to my narrative.
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Humans benefit from the natural world in many ways. These benefits include the products (such as food, fiber, or timber) that we can harvest from nature, or the processes (such as pollination, biological control, or nutrient cycling) that make earth such a nice place to live. Whether people recognize the importance of these so-called “ecosystem services” to our health and well-being varies considerably as a function of education, past experiences with nature, and other socio-economic factors. In fact, some people find abundant ecosystem disservices in nature. For example, some people view natural areas as dangerous places that should be avoided.
A major focus of the Garden Ecology Lab research program is to discover which garden plants may help maximize the ecosystem services of pollination and biocontrol.
In an increasingly urbanized world, where many people lack meaningful interaction with the natural world, how can we help ensure that the importance of nature is recognized and valued? As Robert Michael Pyle wrote in his book The Thunder Tree: Lessons from an Urban Wildland (1998: Oregon State University Press), “What is the extinction of a condor to a child who has never seen a wren?”
One approach to helping society value the natural world is to put a dollar value on it, and that’s just what Robert Costanza and 12 colleagues did over the course of a five-day workshop hosted by the National Center for Ecological Analysis and Synthesis in 1996. A few months later, they published the second global accounting of the monetary value of the ecosystem goods and services of our planet1.
The authors found over 100 studies that valued one or more ecosystem services. They standardized the dollar value of each ecosystem service as the 1995 dollar value per hectare. They noted the location of each study and categorized the biome where the study occurred. They also generated novel estimates of the dollar value of various ecosystem services in various biomes by constructing what were essentially supply and demand curves. With these curves, they mathematically asked questions such as “How much more valuable would pollinators be, if they were endangered?” In this way, they were able to mathematically manipulate supply and demand curves and estimate what is known as the “marginal value” of each ecosystem service. In short, they used a lot of math. On a global map, they measured the area taken up by each biome. They multiplied the dollar value of each ecosystem service per unit area by the area taken up by each biome and developed a global map of sum-total value of ecosystem services.
The authors estimated that the value of the earth’s ecosystem services averaged $33 trillion dollars per year (1995 dollar value), which was 1.8 times the global gross national product. Nutrient cycling represented the highest valued ecosystem service, at $17 trillion per year. Coastal systems were identified as the most valuable biome, at $12 trillion per year.
Urban and suburban areas were included in the study. What struck me about this paper, however, was that the dollar value of ecosystem services of urban areas was not listed. Instead, the authors noted that ecosystem services in urban areas (like desert, rocks, tundra) “do not occur or are known to be negligible.”
When I read this paper as a young Ph.D. student in 1997, I was incensed. My family grew food and raised chickens and rabbits in the backyard of our Baltimore rowhouse (ecosystem service = food). As a child, I captured water striders, turtles, and tadpoles from urban streams (ecosystem service = habitat). As an undergraduate, I loved exploring the urban forests of Patapsco Valley State Park for exercise and stress management (ecosystem service = recreation). Did urban areas really deserve a zero? This paper made me want to study the ecosystem services of cities, just to prove the authors wrong!
Composting is an example of the ecosystem service of waste treatment.
In 2002 I started to study the ecology of urban areas, as an assistant professor of biology at Fordham University in New York City. I collaborated with doctoral student Kevin Matteson to study the value of urban gardens as wildlife habitat and pollinator conservatories. We found that 18 small gardens dotting one of the most urbanized landscapes on earth were used by a diversity of insects, including 24 species of butterfly and 54 species of bee. At this same time, others were also documenting the ecosystem services of urban areas. For example, The New School’s Timon McPhearson estimated that raised bed gardens in New York City annually helped to retain and manage 12 million gallons of stormwater from flooding city streets. Karin Burghardt, as a University of Delaware undergraduate studying with Doug Tallamy, showed how plant choices can increase bird abundance and diversity in suburban gardens in Pennsylvania.
Raised beds in urban areas retain rainwater and reduce run-off and storm system overflows. This is an example of the ecosystem service of disturbance regulation.
In fact, the early 2000s were a heyday for urban ecology research, due in large part to National Science Foundation funding of urban long-term ecological research efforts in Phoenix, Arizona, and Baltimore, Maryland. Whereas less than one-half of one percent of all papers published in nine leading ecological journals between 1995 and 2000 focused on urban systems or urban species (Collins et al. 2000), by 2016 over 1,000 articles, books, and book chapters have been published; and over 130 students have been trained in urban ecology by the Phoenix and Baltimore programs, alone (McPhearson et al. 2016). Despite these advances, the field of urban ecology is still relatively young, and much remains to be discovered.
In 2014, Costanza and colleagues published a new paper, with an updated estimate for the value of our globe’s ecosystem services.2 They estimated that natural systems annually provided $125 trillion (2011 US$ value) in ecosystem services to humanity. At least part of this increase is due to improved documentation of the portfolio of ecosystem services provided by different biomes (see table). And this time, ecosystem services provided by urban areas were valued at $2.3 trillion dollars, or $2.9 trillion in inflation-adjusted dollars for 2020.
Table 1. The Value And Ecosystem Services Provided By Various Biomes On Earth. All dollar values have been inflation adjusted to 2020 dollar values, and are reported as TRILLIONS of dollars. Red Text: Identified as a service in Costanza et al., 1997, but not 2014; Green Text: Identified as a service in Costanza et al., 2014, but not 1997; Black Text: identified as a service across both papers.
[Preface: For the past few years, I have written a column for the Hardy Plant Society of Oregon’s (HPSO) Quarterly Magazine. It has been a wonderful experience, as the HPSO provides excellent editorial assistance. Below, I share my most recent article for the HPSO Quarterly, and thank Eloise Morgan and her team for helping to improve and elevate my writing.]
I spend my nights thinking about gardens: not about the plants that I want to purchase or the crops that I want to plant. Instead, I puzzle over how to study a system that is incredibly variable (from person to person, or even in the same person’s garden from year to year) and complex (with more plant species than just about any other system that has been studied). Gardens are both wild and managed, and unlike other systems I have worked, it is impossible to divorce human behavior from the ecology and evolution of the garden.
In this series, I wanted to share five scientific studies that have had a large role in shaping how I think about gardens. Because of space limitations, I will share the first study in this article. I will wrap up the remaining four studies, in subsequent issues. The five studies are:
Simberloff and Wilson (1969). This study commenced 54 years ago, and yet remains a ‘must read’ for any ecology student. In 1966, Dan Simberloff and Ed Wilson selected six small mangrove islands off the coast of Florida. The islands varied in distance from the mainland coast, from near to far (Figure 1a), as well as size, from small to large (Figure 1b)
Figure 1. In Simberloff and Wilson’s experiment, they selected mangrove islands that varied in their (a) distance from the mainland (the coastline of Florida) and (b) their size. Attribution: Hdelucalowell15 / CC BY-SA (https://creativecommons.org/licenses/by-sa/4.0)
Simberloff and Wilson constructed a scaffold that encircled the edge of each island, covered the scaffold with a tarp, and then proceeded to ‘defaunate’ each island with methyl bromide pesticide. In other words, they killed every arthropod on the islands. After removing their ‘death tents’, and over the course of the next year, they carefully monitored, cataloged, and counted every arthropod that arrived and survived on each island. What they discovered was formulated into the ‘Theory of Island Biogeography’, or a theory about how organisms colonize new habitat, and assemble into a biological community.
They found that islands that were closer to the mainland coast of Florida were colonized earlier, and accumulated species faster, compared to islands that were farther (Figure 2). They also found that species would accumulate on each island, over time, until a maximum peak is reached (not shown). Then, the number of species would begin to drop, as ecological interactions (such as competition for food) would allow some species to prosper, while others went locally extinct. They found that smaller islands were more prone to species extinctions, than larger islands (Figure 2).
Size, distance, age: those are the three things that Simberloff and Wilson predicted would govern the diversity and assembly of organisms within a habitat.
My first faculty position was at Fordham University in New York City, where I studied pollinators in 18 community gardens in Harlem and in the Bronx. During the course of this study, I was inspired by Simberloff and Wilson. I could not help but see the 600+ community gardens that dot the landscape of New York City as islands of green in a sea of concrete.
We expected that gardens that had been long-established would have more pollinator species than newer gardens. We expected that larger gardens would host more pollinator species than smaller gardens. And, we expected that gardens that were closer to ‘mainland’ sources of pollinators, such as Central Park or the New York Botanical Garden, would have more species of pollinator than those that were distant.
We were wrong on two out of three predictions (Matteson and Langellotto 2010). Larger gardens had more pollinator species than smaller gardens, but neither distance nor age had any impact. I was so disappointed that we did not find an effect of distance, or of garden age. I had visions of ‘revitalizing’ the Theory of Island Biogegraphy for urban landscapes, but it was not to be. If anything, our study suggested that the ‘sea of concrete’ was not exactly a wasteland, afterall. The street trees, potted plants, windowsill gardens, and patio gardens all provided resources for urban pollinators, even in one of the most densely populated and heavily developed cities in the world.
This study showed me that it will be much more difficult to track pollinator movements among urban gardens, than I had hoped. We tried to use a traditional mark-recpture approach (see Matteson and Langellotto 2012), but out of 476 marked butterflies we only found four in a garden other than which it was marked and released. We were searching for the ‘needle’ of small butterflies in the ‘haystack’ of the New York City landscape. My students tried to follow pollinators as they left our study gardens, and almost got hit by a car, as they were running across the street. We played around with the molecular markers of a few bumblebees (see Morath 2007), to see if there was evidence of genetic differentiation, but were stymied by a lack of reliable primers that could help us look for any genetic differences in bees from different gardens. And then I moved to the Willamette Valley, where gardens are islands of green in an ocean of green. Understanding what draws pollinators to particular gardens will be even more difficult in this landscape, where pollinators have so many other choices for finding nectar and pollen.
Based upon our initial results from our Portland Garden study (2017-2019), I think I have a new hypothesis as to what might draw pollinators to home and community gardens. Our second study year (2018) was characterized by a hot and dry summer. Our first sampling season was also dry, but the spring months were wet, and the summer was cooler. In 2018, we collected far more bees (abundance) and more types of bees (species) than we collected in 2017 or 2019. In 2018, the landscape of the Willamette Valley was toast! Almost all flowering plant materials seems to shut down photosynthesis, so that they could conserve pressure water that would otherwise escape through open stomates. In this type of situation, bees seemed to concentrate in home gardens, which seemed to be one of the few places where they could reliably find nectar and pollen.
If this is the case, gardens aren’t necessarily going to be an important source of floral resources across all years. In a good year, there should be other plants in bloom in the greater landscape that bees can use. But in a hot, dry year, gardens may become an even more important refuge for bees. Most gardeners provide irrigation, which extends the bloom season beyond what is natural in the valley. Or, gardeners select plants that can prosper and bloom without supplemental irrigation, such as goldenrod or Douglas aster. It’s important to note that, even in the hot, dry weather of 2018, we still collected more bees from gardens that used drip irrigation, rather than overhead sprinklers. I think that the overhead irrigation physically blocks bees from navigating through a garden, which lessens their abundance and diversity.
Ultimately, I hope that our studies can lead us to a more predictive model of the resource value of home gardens to pollinators. The goal isn’t necessarily to understand what gardeners should do to attract pollinators, but to describe the conditions where gardens become increasingly important to pollinator conservation. In addition, I’d love to describe the value of gardens, relative to other habitat types, to pollinators. And finally, I hope to better understand the direction and movement of pollinators between gardens and other habitat types.
Garden research takes a lot of time, patience, and money. For example, the four new research projects that I detailed in an earlier post will cost close to $180,000 *this year, alone* to cover the salary and benefits of one post-doctoral scientist, two graduate students, and three undergraduate student researchers. And that doesn’t cover the cost of materials or supplies, including the 200+ plants that we purchased for two of the studies! We currently cover the costs through a combination of a USDA Fellowship that supports Gwynne, cost-sharing with another research group to support Cara, small grant funds and donations made to our research fund managed by the Agricultural Research Foundation to support Jen and the undergraduate researchers.
Showy milkweed, Asclepias speciosa, at Aaron’s native plant study site. I visited on June 24, 2020, for the first time this year, due to COVID-19 travel restrictions. We will now start measuring floral traits, as part of an effort to develop a predictive model of a plant’s attractiveness to various pollinators.
Ask any scientist that serves as the Principle Investigator (PI’s) of a research group (such as the Garden Ecology Lab at OSU): the hardest part of doing science is ensuring that you have the funds to pay the people that are integral and essential parts of your team.It is the part of my job that I lose sleep over, most often.
This week, the Garden Ecology Lab and Oregon Extension Master Gardener Program received news that literally changes the future for research and Extension in gardens.
Clackamas County Master Gardener Sherry Sheng, and her husband Spike Wadsworth, made a gift of $503,000 to the Oregon State University Foundation, to formally establish the Y. Sherry Sheng and Spike Wadsworth Master Gardener Professorship Fund. This week’s donation creates a gift annuity of $503,000, where payouts will benefit the Professorship Fund. This gift is in addition to the $1.2 million planned estate gift that Sherry and Spike made to the Oregon State University Foundation in 2012. Both gifts will combine (when Sherry and Spike pass away), for a $1.7+ million endowment that will fully fund what I suspect is the very first Endowed Master Gardener Professorship in the United States.
The language describing the intent of the Professorship fund is below:
“The OSU Master Gardener™ Program offers engagement and outreach in communities across Oregon. OSU faculty train volunteers through in-person and online instructions and provide hands-on experience in advising home gardeners.
The personal contacts Master Gardener volunteers provide clients are rooted in the design of the Master Gardener Program: informed by science, accessible to the public, and delivered by trained volunteers in a cost-effective manner.
Quality and effectiveness of the program requires a strong leader in the position of the Statewide Master Gardener Coordinator and the leader’s ability to engage in scientific research. Nearly all of the gardening advice universities dispense to home gardeners are derived from agricultural research. This is because research funding concentrates in commercial crops while there is little to no money to support research in gardens. As a result, gardens are understudied.
The Y. Sherry Sheng and Spike Wadsworth Master Gardener Professorship Fund is intended to support the Master Gardener Program leader’s original research in gardening practices that build soil, conserve water, grow food for people and wildlife, and nurture the human spirit.
It is important to note that the Y Sherry Sheng and Spike Wadsworth Master Gardener Professorship is an estate gift, and will benefit the NEXT generation of garden researchers and Extension professionals. Even though the funds will not be realized for several decades, their contribution and pledge solidifies support for the Master Gardener Program in Oregon with key administrators and decision-makers, and helps to raise the overall profile of the Master Gardener Program.
Oregon’s Master Gardener Program also benefits from endowment funds that currently sit in an Oregon State University Foundation endowment account for the Statewide Master Gardener Program. This fund was established by the Oregon Master Gardener Association in 2004, in collaboration Jan McNeilan and Ray McNeilan. This endowment has since been funded by thousands of grassroots donations, ranging from $10 to $25,000, from individual Master Gardener volunteers, family, and friends, as well as from the Oregon Master Gardener Association and its 22 chapters. The fund currently generates about $10,000 per year, that is or has been used to pay for:
the partial salary of the former Statewide Master Gardener Program Assistant,
the partial salary of the current Statewide Master Gardener Program Outreach Coordinator
bridge funding for Lane, Hood River, Union, and Marion County Master Gardener Programs, when they experienced funding shortfalls,
the Statewide Master Gardener Program Leader’s travel to teach local Master Gardener classes in 27 counties across the state,
creation and maintenace of tools to support Master Gardener volunteerism, including the Volunteer Reporting System, Solve Pest Problems, and the soon-to-be released Plant Clinic Database (known as ECCo, for Extension Client Contact Database).
With all sources of support combined, Oregon’s Master Gardener Program will eventually be supported by the income generated from over $2.5 million in endowed funds. Once again, it is important to note that many of these gifts will not be realized for decades (so I hope, because I genuinely care for the donors!). But when I think about what it will mean for the MG Program in Oregon, it’s a mind-boggling and landscape changing level of support. OSU is going to be the home to the best-resourced Master Gardener Program in the nation, and the support offered by the Y Sherry Sheng and Spike Wadsworth Master Gardener Professorship not only raises the profile of the Master Gardener Program ~ but will attract a unique and highly qualified pool of applicants who are the best leaders, educators, and scientists in the world.
Master Gardener programs in some states often struggle with funding issues. Some states have no statewide program leader, which hampers efforts for coordinated programming, among other things. I don’t know of another Master Gardener Program that maintains a Principle Investigator lab group, such as the Garden Ecology Lab at OSU. Although some Programs engage in research, I don’t know of any that consistently conducts field-based, original research that results in peer-refereed journal publications that are the gold standard for research-based recommendations.
The support that our garden research and Extension programs have received has been a essential to what we have been working to build in the OSU Garden Ecology Lab. Our research on native plants, garden pollinators, garden soils would have never happened without this support.
Moving into the future, the establishment of the first named Professorship for the Master Gardener Program in Oregon is game-changing, and will surely place OSU’s Master Gardener Program among the leaders in home and community gardening research and Extension.
To all of those folks who are currently conducting research in home or community garden systems, no matter where you are . . . keep an eye on OSU. In the future, OSU will be able to offer an irresistable package of support to help you build a world-class research and Extension program focused on gardens.
COVID-19 has impacted our research in many different ways, including making it more difficult to find time to provide research updates on a regular basis. Despite the long silence, we have many projects up and running this summer! In fact, we’re launching four new projects, finishing up three long-term projects, and writing up another two projects.
In this blog post, I give a brief overview of the four new Garden Ecology Lab projects that launched this summer.
Microbiome of Garden Soils and Gardeners: Dr. Gwynne Mhuireach’s project has been spotlighted in a recent blog post and webinar. She has selected the 40 gardeners that will be included in her study: 20 high desert and 20 Willamette Valley gardeners, half of whom are organic and half of whom are conventional gardeners. Soon, these gardeners will be sending in their soil and skin swab samples. And then, the long process of analysis will begin.
She’s studying the microbe community in garden soils, and how those might differ according to garden region (Willamette Valley or high desert) and gardening practices (organic versus conventional soil managmeent). She’s also studying whether garden soil microbes transfer to gardeners’ skin during the act of gardening, and if so, how long those microbes persist on the skin.
Pollinators on Native Plants and Native Cultivars: Jen Hayes is well into the data collection phase of her first field season. She is working with undrgraduates Jay Stiller, Tyler Spofford, and Isabella Messer to: track flowering phenology, measure floral traits, observe pollinator visits to study plots, and collect pollinators so that they can later be curated and identified to species. Jen has written about her research project, in a past blog post. I’ve also set up a Flickr album to host photos from her study.
Native plant and nativar study site, at the Oak Creek Center for Urban Horticulture. A yarrow cultivar, ‘Salmon Beauty’, can be seen in the foreground. Nemophila, Clarkia, and Escholzia cultivars can be seen in the background.
Jen’s field site is located at the Oak Creek Center for Urban Horticulture at OSU, which makes it so much easier for undergraduate student researchers to participate in this project. She samples pollinators on Tuesdays and Fridays. She takes 5-minute observations of pollinator visits on Mondays and Thursdays. In between, lots of time is spent weeding and watering plots, counting flowers, and measuring floral traits.
Cost / Benefit Analysis of Growing Edible Plants in Containers: Tyler Spofford is a new lab member, who is completing his undergraduate degree in the BioResource Research program at OSU. He is working to develop a ‘budget’ for growing food in low-cost containers. I’ve summarized this ‘budget’ data for growing food in standard vegetable gardens, but no data yet exists (that I can find) for containerized vegetable gardens. Tyler is growing 40 tomato plants across two sizes of containers (3 gallons and 5 gallons), as single plants and in combination with basil. He’s keeping track of all of the costs (both money and time spent to grow food). When he harvests food, he’ll weigh his harvest, and track the economic benefit of his efforts, and how container size and planting configuration (one or two crops per container) influences harvest. I’ve set up a Flickr album for his study, to host project photos.
Tyler’s project grew out of my concern that, even though 18,000+ people enrolled in a free, online vegetable gardening course (over 40,000, at last count) ~ that the people who might be most at risk for food insecurity may not be benefitting from Extension Master Gardener resources and information. Tyler’s project is one component of a larger effort to develop more support for renters who might want to grow their own food.
Bucket gardens, on the day that the tomatoes were planted into 5-gallon BiMart buckets. We tried to keep all materials and plants low cost and easily accessible. Photo Credit: Tyler Spofford.
Below is an excerpt from a concept paper I’m writing on the topic:
We know that the COVID-19 pandemic is exerting stress on multiple pressure points related to the economic and food security of U.S. households: more people are in need of food aid and more people are concerned about food access. The U.S. has a long history of gardening in times of national emergency (e.g. Victory Garden of WW I and WWI II, ‘recession gardens’ of 2008). The benefits of gardening as a tool of economic security and resilience are well-established. However, research suggests that these benefits are largely restricted to homeowners. Currently, most state and local laws afford no legal right to renters who want to grow their own food. Community gardens might offer renters opportunities to grow their own food, except that these gardens are often associated with gentrification. To promote public health in the face of economic and health risks of COVID-19 and future pandemics, it is critical to support the food gardening efforts of the most vulnerable. Those in rental housing have been found to be most vulnerable to food insecurity, as well as the food and economic insecurity associated with natural disasters.
Pollinators on Buddleja Cultivars: Cara Still is studying how breeding butterfly bush (Buddleja davidii cultivars) for sterilty impacts the pollinator community that visits Buddleja blossoms. Buddleja davidii and some fertile varieties of this plant are considered noxious weeds in Oregon, and many other places. Normally, noxious weed status would make it illegal to sell or trade butterfly bush in Oregon. However, the Oregon Department of Agriculture allows exceptions for non-sterile cultivars and interspecific hybrids.
Buddleja ‘Buzz Velvet’ (I suspect that plant breeders have a lot of fun, naming new cultivars)
Cara is studying whether or not the plants that are allowed for sale, under the exceptions, still pose a risk of invasion. Our group is working with Cara to document the abundance and diversity of pollinators that visit eight fertile Buddleja cultivars with 16 cultivars that have been bred for sterility.
When I was initially approached to participate in this project, I thought that it should be obvious that sterile cultivars would not attract pollinators. Afterall, sterile cultivars don’t produce pollen, or produce very little pollen. Without pollen, I doubted that bees would visit the plants. But, it is possible that sterile plants would still produce nectar. And, many pollinators ~ such as butterflies and moths ~ visit plants to consume nectar, rather than pollen.
The more I looked into the literature, I realized that no one has yet studied how breeding for sterility might affect a plant’s attractiveness to pollinators. Would sterile forms of butterfly bush no longer attract butterflies? Would sterile varieties attract syrphid flies that visit blossoms for nectar, and not pollen? We’ll let you know what we find, in about a two years. In the meantime, you may want to visit the Flickr album of photos I set up for Cara’s study.
Thanks to all who signed up for the ‘Citizen Science in the Garden!: Studying the Garden(er) Microbiome’ webinar. The webinar recording can be found below, or via THIS LINK.
If you are interested in participating in this project, please leave your information in this short survey. We will work to get back to everyone who responds, within the next month. Depending upon the volume of interest that we receive, it may take a bit longer.
Thanks to all wanting to learn more about the microbiome of garden soils and gardeners!
This post a from Gwynne Mhuireach, who will be studying the microbiome of garden soils . . . and gardeners!!
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A little about me…
Gwynne Mhuireach will be studying the microbiome of garden soils and gardeners!
I am a researcher, farmer, and mom to twin teenagers. My formal education is broadly cross-disciplinary, including degrees in biology, architecture, and landscape architecture. While I was working on my Masters, I began studying microbes inside buildings as a member of the Biology and Built Environment Center at the University of Oregon, where we discovered that our exposure to microorganisms indoors depends a great deal on what microorganisms are present in the immediate outdoors. This line of inquiry was so fascinating that I entered the PhD program in Landscape Architecture to investigate how urban green space might influence the airborne microbial communities that people are exposed to in their daily lives. Ultimately with my research, I aim to gain a deeper understanding of how human health and environmental health are connected through the microbes we share.
In addition to my academic research, I also own and operate a small livestock farm with my two teenagers, Lyric and Cadence, and my partner, Tom. A native Oregonian, I was born and raised on a small farm near Klamath Falls, Oregon, where my family produced (and continues to produce) hay and cattle. Now I choose to continue the agricultural lifestyle that has been my family’s way of life for three generations. Producing food through hard work and stewarding a small piece of land to pass on to my children is very important to me. I believe that having a strong connection to the land is also part of what drives me to study microbes in the context of the outdoors, particularly how we interact intimately with them by getting our hands dirty in the soil.
The Garden(er) Microbiome Project
In partnership with Gail Langellotto, I am launching a new citizen science project called, “Microbes under your fingernails? An exploration of the garden microbiome and potential transferability to human skin.” While soil science is well-developed in terms of nutrients and organic matter needed to keep plants healthy, less is known about the diversity and composition of microbes present in agricultural soils, particularly in small-scale farms and gardens. Astonishingly, despite the likelihood of substantial exposure to soil microbes while gardening, yet we lack even the most basic understanding of how much microbial transfer from soil to skin occurs, what types of microorganisms are transferred, or how long they persist. Through this project, we seek to answer these questions with the help of volunteers—you!
Gardeners who volunteer to participate in this project will be asked to collect soil samples from several different beds in their gardens and from the surface of their hands and/or forearms. There will also be questionnaires that ask for information about garden management practices and daily skin care (use of anti-bacterial soap or lotion, etc.) during the sampling period, which will last 2 days. Volunteers will receive detailed results, including a comprehensive soil health assessment and skin/soil microbiome reports. We will also share our findings with other researchers, farmers/gardeners, and the broader public online and through the Master Gardener network. We anticipate that this citizen science project will not only answer our original research questions, but also shed light on how different management practices can impact garden soil health in different climate zones of Oregon.
If you are interested in participating in this project, I am hosting an informational webinar on Friday, June 5th (2020) at 10am. Registration is required to attend. The webinar will be recorded and posted.
If you are unable to attend, but are still interested in participating, please let us know a bit more about you and your garden by taking this short survey. Please note that for this particular project, we are specifically seeking gardens located in Oregon’s Willamette Valley or High Desert regions.
