The study focused on environmental security in relation to international and national aims of Education for Sustainable Development (ESD) to explore if ESD can be understood as being part of a globally implemented securitization process with national empirical studies in Sweden. The perception of environmental threats was first set with regard to international environmental agreements and, mainly, UNESCO's policy aims of ESD. Expressions, statements and undertakings related to environmental threats were examined through a content analysis of education reform policies. Results demonstrated that the implementation of ESD varied depending on the usage of educational programs and individual understanding of ESD at different societal levels. Individual initiatives among teachers played a significant role in this process. It was also shown that securitization took place both horizontally and vertically and that securitization could be re-activated at the existing societal level although the previous one had ignored the impact of environmental threats to society.