This chapter ofi'ers an evaluative assessment of the fluid, evolving interface between citizen scientists and citizen journalists where the news reporting of environmental issues is concerned, Citizen science, depending on how it is defined, dates back over centuries, and has often been described using a host of different terms - recent examples include 'do-it-yourself science', 'crowdsourced science' or 'democratised science', as well as 'mass scientific collaboration', 'participatory action research', 'volunteer monitoring' or even 'citizen cyberscience' .Just as the relationship between the 'amateur'' and the 'professional' scientist can prove challenging at times, however, such has also proven to be the case between journalists and members of the public who feel compelled to adopt a journalistic role, either temporarily or on a more sustained basis (Allan, 2013; Thorsen and Allan, 2014). Accordingly, we begin by exploring various definitions of citizen science, namely with a view to pinpointing how those definitions have been applied in practice, thereby illuminating corresponding tensions between professional and citizen scientists. We then turn our attention to how citizen journalists have helped to push environmental science onto the public agenda. In addition to scoping the academic literature in this area, we look at examples - including the Deepwater Horizon oil spill off the coast of the United States, and the Fukushima Daiichi nuclear plant meltdown in Japan - to consider how citizen journalists have covered environmental issues, hazards and crises. While many citizens engaged in this work find it personally fulfilling, often regarding it as a contribution to community service, others encounter significant difficulties - including when questions of risk and scientific uncertainty prove controversial. By its end, this chapter will have identified several issues worthy of attention for future efforts to enrich and deepen citizen environmental journalism.