Potential and limits of Citizen Science in assessing ecosystem services of European wetlands

Assessing the state of ecosystem service wetlands provides is an essential prerequisite for protecting and restoring wetlands. Citizen Scientists' (CS) involvement in these assessments assists wetland managers and scientists in data collection, functions as an important component of wetland education, and enhances citizens’ stewardship. However, not all methods developed for citizen scientists are equally suited to support these aspects, requiring the assessment of both their potential and limits.

In our Horizon Europe project Restore4Life (https://restore4life.eu/citizen-science/), we compared Citizen Science methods for assessing water quality, above- and below-ground organic carbon stocks, and plant biodiversity with scientific methods regarding data quality, explanatory power of data, and applicability. We analyzed the suitability of these methods to provide reliable and valuable data for wetland assessments and enhance people's awareness of the importance and sensitivity of wetlands. Our seven study sites included lowland and mountain river floodplains, lake floodplains, and peatlands. We wanted to answer the following questions:

• How well can CS data distinguish different wetland habitats? Which parameters have the largest potential to show differences among wetland habitats?
• How well do CS data reflect scientific data? Which methods/parameters fit well, and which do not?
• How can CS methods be improved to deliver the precision needed for wetland assessments?

Our preliminary results show that the activities significantly increased the participants' environmental education and awareness of wetlands. However, wetland assessment using CS faces several challenges, such as, e.g., restricted access to protected or flooded areas and a limited internet connection, hampering the use of online Apps and GPS. Water quality assessments by non-scientists were especially problematic in organic-rich waters typical for wetlands. Untrained citizen scientists also had problems recognizing cultivated tree species within forests, distinguishing between herbaceous plants and young trees, and determining plant species. Furthermore, citizen scientists showed a strong bias toward selecting easily accessible and less diverse sites for species and above-ground organic carbon determinations, which were not always representative of the respective floodplain forest habitat. Restore4Life is funded by the European Union.