My favorite 4-year-old was turning off the lights in his house before we left for school one morning.

He was happy and enthusiastic about the task because, as he said, "I'm saving penguins!" How does a young child make the connection between saving electricity and saving penguins? I don't know. I do know that he believes he can do something useful and helpful, and he's doing it. For now, that's what matters.

Save-the-planet books are proliferating at every age level. Many are printed with recycled materials and nontoxic soy inks.

"The Earth Book" by Todd Parr is a simple and colorful introduction to planet-saving for children ages 3-6. This book is about things that children can actually do: "I remember to turn off the lights and shut the refrigerator door to save energy because … I love the polar bears and I want the snowmen to stay cool." The book includes a detachable poster titled "Ten Ways I Can Help Save the Earth." No. 10 is "Put my underwear in the freezer when it's hot."

"We Planted a Tree" by Diane Muldrow is also written for very young children. Although it's suggested for ages 5-8, preschoolers will understand the simple terms that explain many of the things that trees provide: shade, blossoms, fruit, cleaner air and healthier soil.

"The Magic School Bus and the Climate Challenge" by Joanna Cole explains greenhouse gases and the effects of global warming in a clear, interesting format that will appeal to children ages 5-8. It works for a wide range of age levels because it can be read superficially or at a greater depth. Ms. Frizzle's class learns that every year, 44,000 pounds of CO2 go into the atmosphere for each person in the United States. The book also gives examples of alternative energy sources and actions that children can take.

"Here Comes the Garbage Barge" by Jonah Winter is a true story illustrated by Chris Sickels with creations of wood, fabric, wire and found objects. The infamous garbage barge left Islip, N.Y., with nearly 3,200 tons of garbage onboard. Islip had been burying its garbage but had to find an alternative when landfills began overflowing and groundwater got polluted. From North Carolina to Mexico, the barge traveled for 6 months and 6,000 miles trying to find anyplace that would accept its increasingly smelly cargo. The media attention generated raised awareness about the countrywide garbage problem and the benefits of recycling. For children ages 4-8.

For all ages, "The New 50 Simple Things You Can Do to Save the Earth" by The Earthworks Group is tried and true with more than a million copies in print. This book gives kids the tools, the practical ideas and the encouragement to make a difference.

"Toby Alone" by Timothee de Fombelle is an unusual book of fiction. I really liked it, but couldn't think how to describe it so that other readers might decide to give it a try. The "Bulletin for the Center of Children's Books" captured what I wanted to say: "The setting … with its attendant environmental conflicts, makes for fresh, original allegory that is never heavy-handed or overbearing." Tree huggers, grades 8-12, will surely enjoy it, but it has enough adventure to appeal to a wider audience.

"We are the Weather Makers: The History of Climate Change" by Tim Flannery was written in 2005 and adapted by Sally Walker in 2009 "For the generation who will act on global warming." Recently, a 30-something guy told me that most people under 30 are convinced of the reality of global warming. Only the older generation is in denial. This guy may be on to something. "Weather Makers" is very specific about what is happening and what needs to be done. It could be a textbook for a course in high school.

Kermit the Frog was famous for saying, "It's not easy being green." But these books make it easier and more appealing than you'd expect.

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