 There are estimated to be about 22,000 humpbacks in the North Pacific.Although Maui's Humpback face many dangers, due to pollution, high-speed commercial vessels, and military sonar testing, their numbers have increased rapidly in recent years, estimated at 7% growth per year.Maui is home to a large rainforest on the northeastern flanks of Haleakalā, which serves as the drainage basin for the rest of the island.