Tuesday, December 23, 2014

10 Cool Gardening Studies Published in 2014

In 2002, my graduate students and I started studying the biodiversity and ecology of gardens in New York City and its suburbs.  Our efforts drew more than a few raised eyebrows.  Some still held onto the dogma that biodiversity studies should be done in pristine habitats in tropical latitudes.  What was the point of studying biodiversity in a temperate, densely populated, highly modified city?

Luckily, in a few short years, the tides have changed.  Many more scientists have begun to embrace gardens as relevant and appropriate sites to do real science.  And as a result, we're learning more than ever before about how to garden in a way that improves environmental health, community health and human health.

So as we close out the year, below is my list of 10 cool garden-related research studies of 2014.  Like most lists of 10, my list is subjective and biased by my personal and professional interests (as well as by what I could find in the one afternoon I dedicated to writing this blog post).  But, I hope that they nonetheless help us better understand how to improve our gardens and other green spaces to promote healthier people and a healthier planet.

1)  Paker et al. 2014. The effect of plant richness and urban garden structure on bird species richness, diversity and community structure.  Landscape and Urban Planning 122: 186-195.
  • Key findings:  Bird species richness was highest when the diversity of trees and shrubs was high, and the amount of garden space taken up by trees and lawn was low.  Native birds preferred native trees.  Fewer birds were present in yards with dogs.  [Species richness is the number of species.  So, a species richness of 34 = 34 species.]
  • Apply it to your garden:  Plan for or work towards a garden that has dense shrubbery, native trees and at least some areas that are not accessible to household pets.  
2)  Lowenstein et al. 2014.  Humans, bees and pollination services in the city: the case of Chicago, IL (USA). Biodiversity and Conservation 23: 2857-2874.  --->  Seriously . . . this study was one of the most exciting I've come across in years! 
  • Key findings:  Bee species richness and pollination services conferred by bees were highest in neighborhoods where human population density was highest.  The mechanism for the association between more people --> more bees --> more pollination was gardens!  Where you have more people, you have more gardens.  Where you have more gardens, you have more flowering plants.  Where you have more flowering plants, you have more bees.
  • Apply it to your garden:  Want to do something good for bees in your garden?  Guess what?  You are ALREADY doing something good for bees, simply by tending a garden that offers flowering plants to pollinators.  Of course, if you couple that with eliminating or reducing pesticides . . . even better!

3)  Garbuzov and Ratnieks 2014. Listmania: the strengths and weakness of lists of garden plants to help pollinators.  BioScience 64: 1019-1026.
  • Key findings:  Many of the 'garden plants for pollinators' lists you come across are based upon the author's personal preferences, rather than on rigorous research.  Some lists had poor plant recommendations, or omitted plants that are known to be great pollinators.
  • Apply it to your garden:  Use a plant list as a starting point, rather than a fixed blueprint for your garden. 
4)  Mini et al. 2014.  Estimation of residential outdoor water use in Los Angeles, California.  Landscape and Urban Planning 127: 124-135.
  • Key findings:  The majority of household water use went to irrigating lawns and gardens.  Households in wealthier neighborhoods consumed 3X more water than households in less affluent neighborhoods.  This relationship is driven by the larger lot sizes and increased garden vegetation of homes in more affluent neighborhoods.  Over a decade, water use declined in LA County by 3.4% (because of rebates and conservation programs), even though the population increased by 9%.  Mandatory water use restrictions (no watering from 9am-4pm; no car washing with hoses; watering limited to 2X per week; no watering during the rain) reduced water use by 35%.  Voluntary water use restrictions reduced water use by 6%. 
  • Apply it to your garden:  Water is an increasingly precious resource.  Even though Oregonian's have not experienced the same drought-related restrictions as our neighbors to the south, it is important to be aware of fact that gardens can be designed and maintained to use less water than we currently use.  Turning even one small part of your garden into a water wise garden has several big benefits.  You conserve water.  You reduce irrigation-induced run-off into Oregon's waterways.  You generally have to spend less time on maintaining a water wise garden.  Triple win!
Photos below by Linda McMahan:  Waterwise plants, Rockrose (left) and Gaillaridia and Hebe (right) use less water than many other garden plants, and still look great in the garden. 

5)  CoDyre et al. 2014.  How does your garden grow? an empirical evaluation of costs and potential of urban gardening.  Urban Forestry and Urban Greening (online first)

  • Key findings:  On average, 50 gardens in Guelph, ON produced 1.43 kg (~ 3 pounds, 2 ounces) of fruits and vegetables.  There was a high amount of variation between gardens, with the least productive garden yielding fruits and vegetables at a rate of $0.34 per square foot and the most productive garden yielding fruits and vegetables at a rate of $2.20 per square foot.  These values are in line with what I found via a review of the literature, also published in 2014.  The least productive garden generated $0.17 per square foot, while the most productive garden generated $2.20 per square foot.
  • Apply it to your garden:  Sometimes, gardeners will joke about the most expensive tomato you'll ever eat . . . because of the time, energy and resources it takes to grow tomatoes (particularly on the Oregon Coast or in the high desert).  But, overall, gardening is a good economic investment.  On average, you'll be able to grow fruits and vegetables at a lower cost compared to what you would pay in the grocery store.  In my study, I noted that some crops were found to be more 'profitable' than others.  These include leafy greens, peas, strawberries, squash and eggplant.  Herbs are another crop that you can grow (often with very little maintenance) and access at a much cheaper cost, compared to what you would pay for fresh herbs in the grocery store.
Photos (both by me!):  Square foot gardening (left) is a popular way to maximize your vegetable harvest in a small space.  Good use of space (right), with leafy greens in a raised bed that is surrounded by strawberries.

6)  Hanks et al. 2014. The impact of school gardens on student salad selection: a pilot study. The FASEB Journal 28(1) 808.12.

Key finding:  When a school salad bar contained greens grown by students in a school garden, the percent of students taking greens from the salad bar increased from 2% (8 students) to 10% (37 students).  Although the majority of students still did not take greens from the salad bar ~ this pilot study showed that the simple act of growing their own food (+ promoting that the food came from the school garden) resulted in a more than 400% increase in the number of students who selected salad greens!  This study aligns with one I publish in 2012, where we showed that garden-based nutrition education programs increased vegetable consumption in kids, whereas nutrition education programs without a gardening component increased nutrition knowledge, but not vegetable consumption.
Apply it to your garden:  If you have kids or grandkids, bring them out into the garden with you.  Help them grow their own food.  Introduce them to new fruits and vegetables through gardening.  Let them take ownership of the food that they grow, and allow them to choose how their crops will be used (as a fresh snack, as part of a recipe, as a salad,  as a side).  

Photo (by my hubby):  My stepson, 15 in this photo, helping me harvest potatoes in our garden.  When I first met my step kids, my husband was using a Jessica Seinfeld approach to getting them to eat fruits and vegetables (e.g. 'hide' vegetables in recipes).  But, we've worked hard over the years to get the kids to help us in the garden and kitchen, and that work has paid off.  My stepdaughter now willingly takes up fresh broccoli and kale.  My stepson loves the winter squashes. 

7)  Locke and Grove 2014.  Doing the hard work where it's easiest: examining the relationship between urban greening programs and social and ecological characteristics. Applied Spatial Analysis and Policy online first).

  • Key finding:  free, urban tree planting programs were deployed, most often, in more affluent neighborhoods where tree canopy cover was relatively high compared to other parts of the city.  The authors suggest that this pattern occurs because it is easier to get affluent households to participate in free tree-planting programs, compared to less affluent households.
  • How I will apply it to my work:  for many years, the Master Gardener program in Oregon has been largely white, older and female.  We have tried, but have had limited success making our programs accessible to a broader diversity of would be Master Gardener volunteers. Like urban tree planting programs, we have a programs that can benefit many people ~ but not all take advantage of our programs.  There are probably many reasons for our lack of success in reaching out to a broader cross-section of Oregonians, but this article reminded me that it's important to truly consider how the way we do things might selectively include or exclude people.
8)  Hanley et al. 2014.  Going native?  flower use by bumblebees in English urban gardens.  Annals of Botany 113: 799-806.
  • Key finding:  bumblebee visitations to native plants did not from visits to non-native plants.  Of the top 6 flowers visited, only 1 was a native plant.  Of five bumblebee species studied, two concentrated on native plants, two concentrated on non-native plants, and the last visited natives and non-natives somewhat equally.  This suggests that the bumblebee species have divided up resource use in the garden (niche partitioning).  Native 'weeds' were important nectar and pollen sources for British bumblebees.
  • How to apply it to your garden:  most bee species are floral generalists.  This means that they are able to visit and collect pollen and nectar from many flowering plants, including non-native plants.  So, if you want to attract more bees into your garden, one of the best things you can do is to plant a lot of flowers.  You don't need to plant only native flowers.  And, if there is any way you can be more tolerant of flowering, non-invasive weeds in the garden, you can gain peace of mind by knowing that you're probably helping out the bees.  Please note, however, that whereas most bees can forage from both native and non-native flowering plants, most butterflies and moths heavily rely on native herbaceous plants, shrubs and trees. 
9)  Pardee and Philpott 2014.  Native plants are the bee's knees:  local and landscape predictors of bee richness and abundance in backyard gardens. Urban Ecosystems 17: 641-659.
  • Key finding:  Okay.  I just told you that the study, above, found that native plants did not result in differences in bee richness in British gardens.  That's largely congruent with what this study found, as well.  Bee species richness did not differ between gardens with and without an abundance of native plants, for all groups except for cavity nesting bees.  Bee species richness was positively associated with floral abundance, shrubby cover, less lawn, and larger vegetable gardens.  But, what this study did find was that bee ABUNDANCE was higher in gardens with more native plants.  So, you may not get a more diverse bee community in gardens dominated by native plants, but you are likely to get a more abundant bee community in such gardens.
  • How to apply to your garden:  Gardens with an abundance of flowering plants are great for bees.  Don't forget, too, to provide habitat for ground-nesting bees (bare ground!  don't mulch everything!) or cavity nesting bees (debris piles of twigs are great for these bees, but balance this with whether or not you are unwittingly providing habitat for rodents).
10)  Goto et al. 2014.  Differential responses of individuals to late-stage dementia to two novel environments: a multimedia room and an interior garden.  Journal of Alzheimer's Disease 42: 985-998.
  • Key finding:  Alzheimer's patients showed positive behavioral changes and exhibited a decreased pulse rate (suggesting a state of calm) when they sat in an indoor, Japanese garden for 15 minutes.  Patients' behavioral and physiological responses were largely negative when they sat in a Snoezelen multi-sensory environment room for 15 minutes.  When patients were brought back into the room that was originally set up as a Japanese garden, after the garden had been replaced with office furniture, they exhibited negative behavioral and physiological responses.
  • How to apply it in your garden:  Gardens are calming.  Many studies show this to be the case at a physiological level.  Take time to enjoy yours.  Consider the garden designs that are most pleasing to your senses.  Take someone you love to visit a garden.  Enjoy the view, and enjoy each other's company.

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