After a resurgence in humpback whale populations following international bans on industrial whaling, these majestic mammals now confront a pressing challenge: global warming.
Unlike some marine species that can adapt to temperature changes, humpback whales are large, ancient mammals that struggle to adjust. Many marine mammals typically respond to rising temperatures by migrating to cooler regions, often toward the poles.
Humpback whales are known for their remarkable migrations, traveling up to 4,830 kilometers from Alaska to Hawaii for breeding. They require specific environmental conditions, with temperatures between 21 and 28 degrees Celsius, essential for the survival of their vulnerable calves.
As global temperatures rise, scientists express concern that humpback whales may need to alter their migration routes. A 2022 study from the University of Hawaii indicates that unchecked greenhouse gas emissions could push many breeding sites beyond the temperature tolerances of these whales. If fossil fuel emissions continue unabated, experts predict that around 67% of humpback breeding sites could experience temperatures that exceed their limits.
To mitigate these impacts, researchers emphasize the need for establishing protected areas that account for potential shifts in whale breeding sites. Some humpbacks may explore new breeding grounds further north, provided the seabed is suitable and free from predators. However, the designation of these protected areas must be tailored to each humpback population's specific needs.
Climate change has already altered humpback whale migration patterns. For instance, researchers off the coast of Massachusetts have noted that the peak occupancy of humpback whales now occurs two weeks later than it did 20 years ago.
Additionally, the feeding grounds of humpback whales are under threat due to climate change. These whales primarily feed on krill, small shrimp-like crustaceans, consuming tons daily before their migration. However, rising temperatures have led to an approximately 80% decline in krill populations since the 1970s.
Consequently, humpback whales are forced to seek alternative food sources, increasing their risk of entanglement in fishing nets and collisions with boats. Furthermore, climate change heightens their susceptibility to diseases, with scientists observing that these whales appear thinner and more infested with parasites.