||Environmental Literacy, Science Literacy, Comparative Study, Delphi Study, Mixed Method, PISA, Pedagogical Content Knowledge, Science Education, STEM Education
||This dissertation analyzes different aspects of environmental literacy. It contains two interrelated research fields. The first research field comprises four studies and focuses on the environmental literacy of 15-years-old students in different counties based on PISA data. The second research field comprises two Delphi studies with experts of environmental education. These studies focus on the concepts, contexts and competences of environmental literate individuals, as well as teacher education aspects. The purpose of research is that in future raw material resources will be consumed faster than today. So, nowadays individuals who are sensitive to the environment are increasingly needed. Therefore, the concept of environmental literacy should be integrated in science education. Moreover, science curricula, textbooks, and teacher education should be revised to integrate the environmental literacy and to develop common universal value for nature, individuals and society. Due to these reasons, there is a need for comprehensive and detailed research on environmental literacy. In this dissertation, one of the aims is to determine the factors that influence the environmental literacy and to compare the environmental literacy of pupils in Germany, Singapore and Estonia. The second purpose is to identify the consensus of experts on environmental literacy to revise the definition and framework of environmental literacy. Finally, it aims to integrate the concept of the environment into teacher education and STEM education. STEM stands for Science, Technology, Engineering, Mathematics, and is a new science education (SE) reform approach in different countries. The first research field includes four studies based on PISA data. In the first research field, it is determined both a the factors that affect the environmental literacy of 15-year old students in Germanya , and a the change in the environmental literacy of German students from 2006 to 2015a , respectively (Study-1 and Study-2). The purpose of Study-3 is to a compare the variance of the main factors affecting the environmental literacy of fifteen-years-old students studying in Singapore, Estonia and Germanya . The aim of the study-4 is to determine both a the dimensions including a effects of family, teacher, student, and teachinga that influence the environmental literacya , and a the effects of environmental perceptions including a environmental awareness, environmental responsibility and environmental optimisma on science literacy (SL)a through using PISA data. In the second research field, it is aimed to reach the consensus of experts on the framework of environmental literacy (study-5) and to determine a what teachers should do to their experiences and qualifications as environmental STEM literate individualsa (study-6) based on responses within Delphi studies. Moreover, this research field demonstrates the necessity of integrating the concept of the environment into STEM education and into pedagogical content knowledge (PCK). Pragmatic Paradigm is adopted as philosophy. As research design, sequential mixed methods are used. In this process of dissertation, the first four studies are designed as quantitative research. After the quantitative studies, the 5th- and 6th-studies are carried out with the Delphi method which includes both qualitative and quantitative studies respectively. This method is an exploratory sequential mixed method approach. The inclusion of environmental literacy within the framework of international large-scale research might expand awareness of environmental literacy. Moreover, the integration of international large-scale research and qualitative research might contribute more to environmental literacy universally. In this way, revision and updating the environmental literacy within the educational system, which is continuously developing, might be realized more effectively. Finally, in further studies related environmental literacy, the factors that affect environmental literacy and framework of the environmental literature, which is obtained from experta s opinions should be also taken into consideration. In addition, the concept of the environment should be integrated into current education reforms especially STEM education and teacher education.