Be sure to browse the category tree on the left hand side of the screen as you can go much broader or more specific than this. The vocab is sorted into three 'tiers' of difficulty. Some of the more basic tier-one words have pictures that show when you click on them, all the others have definitions in English that come up when you click on them.
I have used the higher-level vocab on this website for undergraduate ESL students in Austria when covering 'STEM' and found it worked well. It is student friendly, and as with any ready-to-go vocab list which is actually good enough to use, VERY teacher friendly! I should also add that it's free and doesn't require registration (though you can probably do more with it if you log in).
Once you've made/adapted your list, there's a really good collaborative exercise you can do with it. On Memrise.com (free, login required with e-mail or Google or Facebook) you can create your own flashcard lists, adding pictures and audio to vocab terms. The site then creates fast-pace quizzes to help the initial memorisation of the vocab, keeping track of how well you do. It won't help with using the word in a sentence, but for the "first wash" is very effective.
When the students are gathering pictures/definitions/audio links for the terms, if you delegate small groups to each work on one environmental-science subtopic in their own Google Doc, shared with you, then you can keep oversight of exactly what everyone is doing (even individual students within the groups), whether in class or at home.