What can geotagged photographs tell us about cultural ecosystem services of lakes?

Natural and artificial lakes provide multiple cultural ecosystem services (CES), but they are largely underrepresented in CES assessments, which mostly focus on individual large lakes. Social media data may offer an opportunity to analyse CES of lakes at regional scales. This study therefore aims at exploring the use of photos uploaded to the photo-sharing platform Flickr for analysing CES of 2,807 lakes in the European Alps. We (1) explained the spatial distribution of photo-user-days (PUD), (2) examined the importance of lakes in providing CES, and (3) identified key CES through text analysis of user-generated tags. Our results indicate that good physical accessibility and proximity to densely populated areas mostly increase PUD density, although temporal accessibility is limited to a few summer months for mountain lakes. Based on 418 unique tags, we identified 12 different CES, including aesthetic experiences and recreation. Less prominent CES included sense of place or 'culture & heritage'. Our findings suggest that lakes are important for providing multiple CES, but future research should include user survey data to deepen the understanding of people's perceptions and preferences.