Citizen science to map the flora of the Zurich region, Switzerland

Background/Question/Methods

As a matter of course, densely populated areas have undergone huge environmental changes during last centuries. Surprisingly, such areas often lack careful documentation of how nature or more specifically, fauna and flora have transformed, and hence knowledge on the significance of such changes is limited. In the Zurich region (Switzerland), information on such changes has been compiled by individual scientists. Focusing on the distribution of vascular plants, the last published flora of the administrative Zurich region (covering 1740 km2) dates back to 1839. The Botanical Society of Zurich (BSZ) recently decided to map the current flora in order to trace species compositional changes in space and time for a 180-year time period and to create a consistent basis for future comparisons. Although there is a general goodwill to the flora initiative, only little financial support is expected. The BSZ therefore decided to make public its goals and to motivate volunteering botanists and citizens to spend a total of 3 to 5 weeks contributing to the mapping or collecting herbarium information. To motivate the participation of a wide range of volunteers, a sampling design has been chosen that systematically covers one ninth of the area in units of 1 km2. Also, instruction camps have been organised where both botanists and lay persons come together and practice to properly key out species. During the first one-week camp, mapping methods were tested by 40 persons, which resulted in guidelines for properly collecting plant species and estimating their abundance.

Results/Conclusions

During this pilot event, 15 quadrats were mapped by one or two teams each, which produced 320 plant species per quadrat. Best estimator of species richness was walking distance and time effort (r2=0.62 and 0.54, respectively). Accordingly, we defined for the quadratic mapping units a general time effort of 40 to 60 hours per team of 2 to 4, and a general walking distance of 15 to 30 km. In comparison to results from a cantonal administration programme for monitoring alien plant species, seven times more neophytes were found in the 15 quadrats, i.e. 30 species per quadrat and 128 in total. Our approach of citizen science, which encompasses 100 volunteering experts and lay persons at the moment, is promising not only in that it produces valuable new data in a short time but also because it gives people the awareness of doing something useful for the society – beyond joy, fun and company.