Geospatial crowdsourcing applications are emerging systems that enable researchers to collect important in­formation that otherwise would be difficult to obtain. In biodiversity monitoring, crowdsourcing is a promising approach as it benefits from a large group of people with an often underestimated biodiversity and taxonomy knowledge. Despite its huge potential, crowdsourcing approaches are still underrepresented in biodiversity monitoring. We here evaluate a participatory crowdsourcing web mapping platform that was developed to get information about geographic locations and biodiversity characteristics of urban ponds in the Geneva cross-border region. An important fraction of urban ponds is assumed to be located on private grounds, which makes the participatory crowdsourcing approach very valuable. A media campaign was initiated, encouraging citizens participate and to digitize ponds. In this paper we a) evaluate and discuss the impact of the media campaign on the usage behaviour and history of citizens using the crowdsourcing platform and b) assess the quality of the digitized data that has been collected. This study shows that through media campaigns, citizens can be mobilized and motivated to participate in biodiversity crowdsourcing projects. Results indicate that large quantities of users were recruited through social media. However, only a small fraction of about 3% of the mobilized people digitized ponds on the platform. The majority of these users (68%) digitized one pond while 32% digitized two or more ponds. This study shows that it is important for crowdsourcing platforms to be designed and planned in order to facilitate its usage. However, it is crucial for the success of such cam­paigns to offer something in return to the users and to encourage them to interact among themselves. We suggest that future crowdsourcing biodiversity mapping campaigns should have mobile-optimized interfaces. Mobile devices have the potential to e. g. automatically register ...