Ecosystems Plants & People

Citizen Science meets Urban Botany in Zürich

A citizen science project improves appreciation of plants and the ecological processes they play a part in.

How can you bring nature to an urban audience? A project by Kevin Vega and colleagues at ETH Zürich has shown that you don’t need to bring nature to people. It’s already here. In doing so, they highlight how there’s more to urban botany than spotting plants in the city.

Lake Zurich. Image by Canva.

The core of the project was simple. If you leave a tray of bare soil out in Zürich, what turns up? Wo Samen fallen (Where Seeds Fall) recruited volunteers in 2017. They left trays in their gardens and on balconies.

“We set up the project with several key expectations,” write Vega and colleagues. “(a) The types of plants that colonized participants’ trays would be primarily wind‐dispersed ruderal species; (b) Location would matter—greater amounts of gardens and flowering green space in the surrounding of the tray would increase the number and diversity of plants that were found and—due to the nature of wind‐dispersal—trays on the ground level would have a greater chance of species colonization than those on a balcony; (c) Following their participation in the project and the associated outreach events, participants would show a greater interest in and a more positive perception of spontaneous urban species as well as the kinds of green spaces which surround their gardens.”

“We hoped to inspire questions such as: Why do we call certain species (unwanted) weeds? Why do we deliberately plant certain species? To what extent do we accept the wild life of urban species that is not planned and designed by us humans? What do these species need to live their life in our neighborhood?”

They provided participants with a plastic planter tray 39.5 × 29.5 × 9 cm in size. The volunteers filled the trays with seed-free potting soil. Any plants in the tray had to arrive from outside. “For those placed on ground level, we advised our volunteers to select a flat open‐air area protected from disturbances such as cats or lawn mowers, and we encouraged them to place chicken wire over the tops of the trays for further protection,” write the authors.

Once the trays were set, it was a matter of watching. The team asked people to photograph their trays every month and upload the photos to the project’s website. On the website, participants could then see other people’s trays. I think this is important. While a negative result is as important as a positive result, it would be dispiriting to have only your own negative result to look at.

At the end of the season, the volunteers brought their trays to an event. Here, botanists identified what they found in them. As they expected, most of the plants were wind-dispersed. While trays in gardens had more species than trays on balconies, the result wasn’t statistically significant. A problem with that conclusion might be down to reporting, say the botanists. “…it is important to note that we believe many participants with no growth simply did not report their data which clearly affects the results.”

As far as the botanical results go, Vega and colleagues report high diversity of plants in trays (alpha diversity) and between trays (beta diversity). However, there were social results too. Participants not only thought about what makes a plant a “weed” but also about the ecological processes that brought plants to the tray. “We intended to highlight ecological connectivity as also indicated by the name of the project.” write Vega and colleagues. “In contrast, we initially considered the need to use commercial soil bought from a garden center in order to avoid the confounding of our results through germination from the existing seed bank as only a methodological concession. While explaining the reason for this to participants, however, we realized that it also helped us to address another type of blindness: soil blindness. We explained the importance of soil seed banks for the persistence of plant populations and more generally the great importance of soils for the ecology of a city.”

Window Box in Zurich. Image by Canva.

There’s a lot to like about this project. I particularly like the low-cost replicability. Nothing is stopping me from getting the equipment at the weekend and running the experiment myself. For anyone looking into running an outreach event, there is value in re-running the experiment. The greatest barrier to running the experiment is the ability to identify local plants. It might be low-tech, but running the experiment in people’s homes gives it a very personal connection.

Another exciting feature is the experiment gets people exploring urban colonization as a process. I recently heard James Wong explain why people can find plants boring. They’re often discussed like they’re soft furnishing for gardens. Instead of being passive objects, this experiment emphasizes the dynamic nature of urban ecology. These plants are moving into these trays. I think that’s important for conservation. Plants as urban decoration are replaceable and interchangeable. Plants that are participants in ecological relationships are not.

The pay-off of getting people to examine the ecological processes of plants is that they have a greater sense of ownership of their environment. Vega and colleagues make clear the importance of this in their conclusion. “…only by closely linking these plants to the life of urban residents can we hope to successfully improve and expand urban green space and urban nature promotion (including the awareness to wisely integrate small urban vegetation patches such as tree discs or roadsides, or less often mowed patches in a lawn). Any such efforts without public interest and support are unlikely to succeed.”