In September 2009, researcher BJ Kirschhoffer was studying polar bears in Churchill, Canada. There were bears everywhere, but something strange was happening to the animals. Some did not look healthy. Many of them were skinny--BJ could even see their ribs through their white fur. These were not well-fed bears. BJ knew that something was very wrong, but what was causing this problem? In Polar Bear: Shrinking Ice, kids go on a real-life adventure with...