I LOVE that book. It's so good. If you're looking for an extension project I would have them do research projects in pairs or small teams about different conservation efforts. Maybe have them pick a local problem or issue and see if they can come up with posters or fliers or even a brochure detailing statistics or facts. They could also give persuasive speeches telling their classmates about why students should _____. So if you live near the beach it might be about preserving sand dunes and why that's important or not littering on the beaches. If you live in the mountains it might be good for them to think about why trees are important and how cutting down trees affects mountains through erosion. There should be tons of things they could pick. Let them get creative but best of all you can tie it in to science, writing and even give them some instruction or practice with research.