Enter your search terms and use the options on the left side of the results screen to refine your search. From there you can quickly get to the full text online. Try searching the following keywords (& others), and then limit to journals & dissertations. Check for relevant subjects:
"ecocriticism theater" "habitat conservation"
"habitat destruction" "sustainable agriculture"
"animal welfare" "animal rights"
"animal rights movement" "energy conservation"
"sustainable energy" "alternative energy sources"
coal "clean energy" "green revolution"
MLA is the main database for literary criticism and allows for very specific thematic searching (e.g., ecocriticism and (theater or drama*) or ecocriticism more broadly).