The following two Guides to the basics of International Environmental Law research are recommended as starting points:
American Society of International Law Research Guide to International Environmental Law uses a clear, well-organized narrative format and includes an introduction/overview of international environmental law research, search strategies, and long, descriptive lists of primary and secondary sources The organization is wonderful, the short explanations are great, and the multitude of easy-to-use hyperlinks are perfect.
The GlobaLex Basic Guide to International Environmental Legal Research also uses a clear, well-organized narrative format and includes an introduction, starting points, and key abbreviations. Treaties are organized by topic, with links to the web site for each treaty. It includes links and descriptions of indexes and finding aids for treaty research as well as to the resources for national laws relating to environmental law, suggestions for searching library catalogs, and a great deal more.
Other sections of this LibGuide, such as Books and Westlaw, Lexis, Bloomberg Law will be helpful when searching for international environmental law resources. The resources listed below will also be especially helpful.