Online social media represent an extensive, opportunistic source of behavioral data and revealed preferences for ecosystem services (ES) analysis. Such data may allow to advance the approach, scale and timespan to which ES are assessed, mapping and valued. This is especially relevant in the context of developing regions whose decision support tools are often limited by a lack of resources and funding. This research presents an economic valuation tool for recreational ES, suitable at wide spatial scales, relying on crowdsourced metadata from social media with a proof of concept tested on an Indian tropical Ramsar wetland. We demonstrate how geotagged photographs from Flickr can be used in the context of a developing country to (i) map nature-based recreation patterns, (ii) value recreational ecosystem services, and (iii) investigate how recreational benefits are affected by changes in ecosystem quality. The case-study application is the Vembanad Lake in Kerala, India, and the adjacent backwaters. Geographic Information Systems are implemented to extract 4328 Flickr photographs that are used to map hot spots of recreation and infer the home location of wetland visitors from within Kerala state with good accuracy. An individual, single-site travel cost demand function is generated and estimated using both Poisson and Negative Binomial regressions, which results in mean consumer surplus estimates between Rs. 2227–3953 ($34–$62) per visit and annual domestic recreation benefits of Rs. 7.53–13.37 billion ($115.5–$205 million) in the investigated wetlands. Improvement in water quality to a level that supports wildlife and fisheries is projected to result in a Rs. 260 million ($4 million) annual increase in recreational benefits, while restoring previously encroached lake area would result in almost Rs. 50 million ($760,000) in yearly value increase. [ABSTRACT FROM AUTHOR]