Testing the feasibility of citizen science to record impacts of invasive alien plants

1. Evidence of impacts of invasive alien species is necessary to inform risk assessments and management decisions but is lacking for many species. Citizen science has become increasingly popular to record invasive species occurrences, but so far has not been applied to the recording of impacts.
2. We conducted an innovative pilot study in Great Britain to explore if citizen scientists could be involved in the recording of vegetation impacts of invasive alien plants. We designed a sampling protocol asking participants to count species numbers and record coverage of the target invasive plant and non-target plants in 3 m2 invaded and non-invaded control plots. We implemented the protocol in a paper version and in a smartphone recording application and provided training in a series of six workshops.
3. The project attracted 37 participants to the workshops, of whom 19 conducted surveys with a clear preference for the smartphone application. Our analysis of the survey data found reduced species richness, Shannon and Simpson diversity and lower coverage of non-target vegetation in invaded plots compared to the control plots. Citizen scientists were most engaged when they attended the workshops. The project was limited by the low participation, the resulting small sample size, the short project duration and problems with plant identifications to species level.
4. Practical implication. The citizen science approach for impact recording has the potential to support invasive species management by providing evidence useful for prioritisation of further research, horizon-scanning activities and management. We recommend continued engagement with citizen scientists beyond an introductory event and a simplified sampling protocol focused on species counts and vegetation coverage rather than identification to species level by inexperienced participants.