Books have a responsibility to teach. That's all this is. It's a tool.
Is the dichotomy too much? A picture book.... about the end of the world... it's teaching consequence...
There are consequences to mistreating the environment, and children need to be taught that. I know they hear about it at school and learn which leaves are which, and that frogs eat bugs, and bees are important pollinators, but that's just stating the obvious. What about opening the class with - What if there were no more frogs or bees or trees? How about that for an entrance? Then you explain the negative effects of losing trees like: no more oxygen, or if the bee's disappear: no more fruits and vegetables. Lead with the frightening possibilities of a world without, and then get into how to make sure none of that stuff ever happens.
An Angry Earth is the first of its kind to teach about an apocalyptic end via a picture book. It gives the worst case scenario. It also does so with graphic pen and ink illustrations. The author/illustrator is not going to offer a rainbow of colours to keep your attention, no. He's offering you a chance to understand the consequences of your actions or inactions where our environment is concerned. So pick up a copy and read through it. If you want your kids to read it, give it to them. If nothing else, it will make them think, and maybe even ask you questions about what they can do to prevent an apocalyptic end.