Coastal landscapes are popular with millions of people globally engaging with them including for tourism and recreation. Monitoring engagement with natural coastal landscapes, including who visits, when and where, as well as what people talk about and value about them is important, including for tourism and recreation and landscape management. Increasingly data from social media have been used to monitor visitation and public discourse about different landscapes, overcoming some limitations with traditional methods. The overarching aim of this thesis is to understand how social media data can be used to assess how people engage with coastal landscapes by: (i) reviewing the academic literature on the use of social media to assess nature-based tourism broadly, (ii) examining how can social media be used to assess tourism and recreation in coastal landscapes at different spatial scales, (iii) assessing how social media can be used to understand public engagement with coastal landscapes, and (iv) understanding how social media can be used to assess how people feel about coastal landscapes. First, to assess the current status of research examining how social media can be used to assess nature-based tourism, a systematic quantitative literature review was conducted (Chapter 2). Such research is novel, with the first paper in 2013 and only 48 papers published up to June 2018 and most research is from Europe and North America. Data obtained from social media included image, text and/or GPS location/route-data, with Flickr, an image-based social media platform, the most commonly researched. Studies often compared results obtained from social media platforms with other methods or among locations. Research included spatial and temporal analyses, assessing cultural ecosystem services, calculating economic values and analysing sentiments expressed in posts, but few referred to ethical issues. It also highlighted other benefits and limitations with social media as a source of data. Important research gaps were highlighted including the need for research in more diverse locations, using other platforms such as Twitter, but also more research assessing Flickr as it provides geolocated data on how and when people interact with nature. Next, beach popularity was assessed in Australia at a continental scale using metadata from 32,383 Flickr images tagged “beaches” and “Australia” posted by 1,254 Australians, and 1,154 international tourists (Chapter 3). There were seasonal patterns in visitation with beaches in the south of Australia more popular in summer, but northern beaches more popular in winter. There was concentrated use of a relatively small area of the extensive coastline, with Australians preferring beaches within capital cities, while beaches in urban areas outside of major cities were more popular with international tourists. The words used to describe the images helped identify ten particularly popular beaches and people mainly expressed mainly positive emotions about the beaches. The results showed how social media data can be used to assess tourism and recreation demand at larger scales including for popular beaches. To assess beach popularity at a more local scale, Flickr image metadata for the popular tourism city of the Gold Coast, Australia, was assessed (Chapter 4). There were nearly 7,000 images of beaches, posted by 908 people, including locals (2,388 images), other Australian nationals (964) and international tourists (1,444), with other accounts not disclaiming were they were from. Locals and other nationals preferred visiting beaches early in the day and on weekends. More remote beaches were popular with locals, while beaches with lookouts were more popular with other nationals and more urbanised beaches popular with international tourists. Words used to describe images included geographical locations, natural features and events or activities. These results show that coastal landscape managers can get important information on where to allocate facilities and resources, improve access, amenities and safety infrastructure for beach tourism and recreation using a readily accessible, low cost, and continuous source of data. Lastly, Twitter data were used to examine public discourse in English and Portuguese about Arrábida Natural Park, a popular natural coastal park in Portugal, Europe (Chapter 5). This involved conducting a quantitative analysis of the content and sentiments in tweets sent by locals (920 tweets), other nationals (675) and those from other countries (465) that included the search word “Arrábida”. Tweets were mainly in Portuguese (67%) or English (29%), and often talked about natural features (58%), park visitation (17%), activities and regional food (14%) or environmental issues (10%). Locals and other nationals posted similar content in tweets, compared to international tweeters. Tweets were mostly positive (68%), but more negative emotions were expressed when tweeting about environmental issues. The results demonstrate how Twitter can be used in public engagement for coastal protected areas, including assessing what people value about these landscapes, what they are concerned about and were there may be conflicts. The literature review and three research studies illustrate how using social media data, data can assist in understanding how people engage with coastal landscapes. This is despite limitations such as fluctuations in popularity and access to data, limited demographic data and ethical and privacy norms. Online user-generated content in the form of billions of posts sent daily to social media platforms, including text and geolocated data, can be used as to complement other approaches for large and local scale monitoring of the development of adaptive landscapes and provide important insights about public engagement for the management of coastal landscapes.