City Nature Challenge: a multi-city Citizen Science approach for monitoring urban biodiversity

City Nature Challenge (CNC) is an international citizen science initiative, promoted by the Natural History Museum of Los Angeles County and the California Academy of Sciences. The challenge, which aims at increasing the knowledge of urban nature through public participation, involves cities from several countries. In Europe, the European Citizen Science Association (ECSA) collaborated with partners to conduct a coordinated evaluation of events during CNC. ECSA is a non-profit association that encourages the growth of the citizen science movement across the continent and advances in research on this topic.