GUEST BLOGGER NANCY CASTALDO
What happens when people come together to clean up a dirty river? In Whales in the City by Nancy Castaldo, young readers discover the powerful story of how the Hudson River—a once-polluted waterway—was brought back to life, making it safe again for whales to return to the waters around Manhattan Island after abandoning them for over 100 years to live, feed, and raise young! This nonfiction picture book will spark conversations about science, nature, water pollution, and how young students can help protect our environment.
Look at the learning objectives
- Understand that whales once left New York Harbor because the water was too polluted.
- Learn how people helped clean the Hudson River, allowing whales to return.
- Explore how science and teamwork protect animals and their habitats.
- Practice reading comprehension, prediction, compare/contrast, and simple environmental concepts.
Pre-reading activity: Then and Now
Materials: Chart paper or whiteboard, markers
Ask students if what they think animals need to live safely near or in a city. Draw a T-chart on the class white board labeled :
Then: Hudson River 100 years ago | Now: Hudson River Today
Leave the chart mostly blank for now and have students fill it during a post-read discussion.
Read: Whales in the City by Nancy Castaldo, illustrated by Chuck Groenink.
As you read to students, pause to look at images of the river then and now. Emphasize key vocabulary: pollution, clean-up, habitat, scientists, recovery. Ask questions like:
- “Why did the whales leave?”
- “What did people do to help the river?”
- “How do scientists know whales are back?”
Science connection: River detectives
Objective: Understand how pollution affects water and how clean-up makes a difference.
- Fill two clear containers with clean water.
- Keep one clean. Ask students to add ‘pollution’ such as bits of mud, trash, oil drops, spoons of paint, to the other.
- Ask students comparative questions: “Which one would you want to swim in?”, “Which is healthier for whales’ bodies?”, “Which is better for their food source to grow in?”
Discuss:
- “How did the Hudson River change over time?”
- “Why is clean water important for whales—and for us?”
Art activity: A river worth saving
Divide your paper in half. On one side: dark water, garbage, sad animals, and big boats.
On the other: blue water, fish, whales, birds, and sail boats.
Add the captions:
- “This river is not safe.”
- “Now whales are back!”
Following book reading and activities, ask students:
- “What can we do to keep rivers and oceans clean?”
- “How do you think the whales feel swimming in the water now?”
Make a list together on a whiteboard of the actions everyone can take. Possibilities include:
- Never litter
- Recycle
- Use less plastic
- Talk to others about protecting animals
Writing prompt
“If I saw a whale in the water, I would…”
Encourage students to draw and write one or two sentences, write a poem to express how they’d feel, or what they’d do if they saw a whale swimming near their city.
Revisit the Then and Now chart
Fill in the chart together, such as:
| Then | Now |
| Dirty water | Clean water |
| No whales | Whales have returned |
| Trash and oil | Fish, birds, and whales live there |
| People didn’t take care of it | People worked hard to fix it |
Say together:
“We can all make a difference!”
Whales in the City is more than a science story—it’s a hopeful reminder that when people work together we can fix what’s broken in nature. Even young children can be environmental heroes!
I hope this book will be a spark that inspires your students to protect the world around them because even rivers in big cities can be wild and full of wonder again.
Featured image credit: “Humpback Whale” by Christopher.Michel is licensed under CC BY 2.0.
Award-winning author Nancy Castaldo has been writing picture books, chapter books, middle grade, and young adult books about our planet for decades. Her work has received numerous honors, including the Green Earth Book Award, two Crystal Kite Awards, the NSTA Best STEM Book designation, Eureka Silver Honors, ALA Notable, two Riverby Awards, and multiple Junior Library Guild Gold selections. Nancy believes in the power of individuals to make a difference—a message that resonates throughout all her books. While her research has taken her across the globe, her recent releases, Whales in the City and Riverkeeper, focus closer to her Hudson Valley home. Both provide a model for global change. Connect with Nancy on BlueSky, X, Facebook, Instagram, and Pinterest. Learn more at https://nancycastaldo.com.
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