Heroes of the Environment: True Stories of People Who Are Helping to Protect Our Planet by Harriet Rohmer with illustrations by Julie McLaughlin is a terrific collection of minibios. No big names here, at least, none I'd heard of. These are stories of people who became immersed in an environmental situation. One of the things that's so good about this book is that in writing about the people, Rohmer writes about the issues they deal with.
I was grabbed right away by the first story about Will Allen who works with city farms. There are also stories here about people who are making use of salvaged materials (I learned about deconstructing buildings instead of demolishing them), bringing solar power to a Hopi reservation, and treating sewage with plants. This is an ethnically diverse group of people, giving readers the feeling that environmental concerns are shared by everyone. As, of course, they are and should be.
I also picked up a number of little scientific/technical details from this book in a painless way, which is how I like to pick them up.
The publisher suggests this book for older elementary school students.