Tong, a lecturer in digital media and culture in the UK, and Zuo, an information technology consultant and data scientist specializing in data mining, data analysis, and natural language processing, examine Twitter discourses and networks about environmental considerations in the discussions about the UK's 2016 referendum to leave the European Union and its aftermath. They consider how the discourse is constructed in tweets on the environmental aspects of the referendum; how users were connected to each other in this environmental communication; which social actors influenced the discourses and networks and how they did so; and what the discourses, networks, and roles played by social actors suggest about environmental politics on Twitter and in the UK. They draw on discourse and network analysis of about 112,000 related tweets collected in real time between May and July 2016, discussing the relationship between environmental issues and politics and between Brexit and the environment; the media landscape within which Twitter exists and key debates in the fields of Twitter communication and environmental communication on Twitter; environmental discourses in tweets and the nature of the environmental considerations in the discussion about the referendum on Twitter; elite domination on Twitter; social network analysis of the environmental data; the tweeting practices and discursive arguments of influential social actors; and insights from the study about social media and environmental politics and social media research and their methodological approach. The book originated from the authors' paper presented at the International Environmental Communication Association Annual Conference in 2017 in the UK.