Canberra: Blue whales, the largest animals on Earth, are facing a serious threat from climate change, according to an Australian marine biologist. Karen Adiwen, a researcher at the Australian National University, said that the migration of pygmy blue whales, a subspecies of blue whales, from their breeding grounds near Timor Leste to Australian waters has been delayed by four to six weeks due to warming oceans.
Pygmy blue whales are normally seen off the coast of Timor Leste, an island nation in Southeast Asia, in October and November, before they head south to feed on krill in cooler waters. However, Adiwen, who has been studying the whales for over a decade, said that she has not spotted any whales in the area for the past six weeks.
“I’m extremely concerned because this is unprecedented,” Adiwen told the Australian Broadcasting Corporation (ABC) on Monday. “We’ve never seen this before in the 12 years that we’ve been working in Timor Leste.”
Adiwen, who is also a member of the International Union for Conservation of Nature’s World Commission on Protected Areas, said that climate change is altering the oceanography of the region, affecting the availability and distribution of food for the whales. She said that warmer ocean temperatures reduce the productivity of phytoplankton, the microscopic plants that form the base of the marine food web, and consequently the abundance of krill, the main prey of pygmy blue whales.
“We are seeing major changes in the oceanography of the region, particularly in the context of rising temperatures,” Adiwen said. “Climate change is having an impact on blue whale migration and delaying the season by four to six weeks. We are also seeing impacts on the actual health of the animals.”
Adiwen said that she observed signs of malnutrition in some of the whales that she encountered during their 2022 southern migration, which she attributed to the lack of food in their feeding grounds. She said that malnourished whales are more vulnerable to diseases, parasites, predators and human activities, such as fishing and shipping.
The situation is worsened by the occurrence of El Niño, a climatic phenomenon that causes warmer and drier weather in Australia and lower ocean temperatures in the north. The Australian Bureau of Meteorology declared an El Niño event in the Pacific in September, which is expected to last until early 2024. Adiwen said that El Niño should increase the food supply for the whales in the north, but it also disrupts the normal patterns of wind and currents that drive their migration.
“It’s a double-edged sword,” Adiwen said. “On one hand, El Niño may provide more food for the whales in the north, but on the other hand, it may confuse them and delay their migration to the south, where they need to replenish their energy reserves.”
Adiwen said that she hopes to see the whales soon in Timor Leste and that she will continue to monitor their movements and health using satellite tags and acoustic devices. She said that the pygmy blue whales are a vital part of the marine ecosystem and the culture of Timor Leste and that their conservation is a global responsibility.
“Pygmy blue whales are amazing creatures that can travel thousands of kilometers across the ocean,” Adiwen said. “They are also very important for the people of Timor Leste, who have a strong connection with them and their songs. We need to protect them and their habitat from the threats of climate change and human activities.”