Gardeners for Biodiversity: How Surveys can Help Quantify Diversity in Urban Areas

July 24, 2019July 24, 2019 Riley Lovejoy 0 Comments biodiversity, Conservation, gardens, urban

Young, C., Frey, D., Moretti, M., and Bauer, N. (2019). Research Note: Garden-owner reported habitat heterogeneity predicts plant species richness in urban gardens. Landscape and Urban Planning. 185:222-227.

https://doi.org/10.1016/j.landurbplan.2019.01.013

Difficult Data

When you hear the term “biodiversity,” chances are you think immediately of the tropics. While there are several hotspots of biodiversity in the tropics that deservedly garner a lot of attention, the conservation of diverse communities of species is important even in your own backyard.

Personal gardens can harbor a surprising number of species even though they are relatively small. Their small size, however, can make them difficult to study. The time and monetary costs of having scientific experts travel to every garden spread out across a large area are often prohibitive. Because of this, many researchers have been studying how to gain information about the biodiversity of individual gardens directly from the people who tend them. This can be difficult, however, as the reliability of the data may be questionable. One gardener, for example, may count the same number of species in their garden as an expert, while another greatly over- or under-counts them.

In this study, the authors, Christopher Young and colleagues, aimed to determine a simple method by which gardeners could provide data on the number of species in their garden without having to try and count them. Different land use types and features (such as compost piles, lawns, etc.) as well as differences in soil and light availability can lead to predictable types and numbers of species. Understanding this, the authors proposed and tested a method by which gardeners may provide valuable information on biodiversity. This includes answering one question related to the variety of habitat in their gardens and another in which the species richness of plants in their gardens is visually assessed.

To study all the home gardens in an area such as this would be a daunting task. If the number of species from each garden could be estimated based on a simple survey given to garden owners, however, valuable information could be learned about the state of biodiversity without so much effort. *Source*: https://commons.wikimedia.org/wiki/Category:Detached_houses#/media/File:Calgary_-_Monterey_Park_-_Park_01.jpg

Studying Surveys

The authors first conducted full expert inventories of the plant species present in each of 83 study gardens. Then, garden owners were asked to respond to two survey questions.

Because different garden features often reflect differences in available habitat, the first question provided a list of features often present in gardens. To respond, garden owners were directed to put a checkmark by the features included in theirs. The second question showed four pictures of lawns, meadows, flower beds, and vegetable patches with varying numbers of species, and gardeners were asked to select the one that most closely matched the same type of space present within their garden.

Once the completed surveys had been received, the authors used the data from the expert species inventories along with survey results to produce statistical models to try and estimate the number of species from the survey results alone. They also tested to see whether responses related to habitat availability or species number were better predictors of actual species richness.

A beautiful example of a home garden with a variety of habitat features. *Source*: https://commons.wikimedia.org/wiki/File:Oklahoma_Gardens_@_Home_009.jpg

Reporting Richness

Just by asking two basic questions about the habitat and species abundance of gardens, about 50% of the actual variation in the number of species could be predicted. Additionally, responses to the habitat availability question were found to more strongly predict actual plant richness than the species number estimates. Though the information gleaned from study participants was only an estimation, any reliable information on species richness can be valuable. The brief and simple survey could be beneficial, as garden owners could quickly and easily provide information about the number of species in their gardens. Further, this type of method can be used to determine species estimates for native, spontaneous, and cultivated plants within the garden. Information from such studies could also provide data on relative species richness between different gardens, and that could be especially relevant to biodiversity. Applied across study areas and combined with other research, the insights gleaned from similar surveys could help scientists better understand how biodiversity is structured across urban areas.

Gardening for Good

Urban spaces are becoming more common, and sadly a lot of habitat for plants and animals is being destroyed in the process. Promoting green spaces amid urban areas can provide refuge for organisms and foster biodiversity. To help make your garden a haven for local biota, consider incorporating sources of water and food (like berry plants or birdseed), along with shelter such as nesting areas, into its design. This checklist from FortWhyte Alive’s Naturescape program has some great suggestions.

Want to learn about how gardening can impact personal well-being? Check out this article from Kristofor Husted at NPR’s The Salt. This article by Raymond, et al. 2018 from the journal Local Environment examines how fostering biodiversity can be beneficial to gardeners.

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