Humpback whales off the coast of Japan: a benchmark of climate change

The coast of the Japanese island of Miyakejima is one of the calving areas and is visited every year by dozens of humpback whales that migrate from the cold polar regions to warm waters to mate. But this was not always the case. The Kuroshio Current, which has been shifting increasingly since 2017, and global warming have caused water temperatures to rise sharply over the last decade. What initially appeared to be beneficial for the reproductive behavior of humpback whales might now have serious consequences in the long term. That's because while the warming of the waters may temporarily create better calving conditions for humpback whales, the changes in the Kurishio Current are causing an imbalance in the marine ecosystem. This can affect food resources and migration patterns and, in the long term, even endanger the populations of humpback whales and other marine animals.

The oceans are getting warmer and warmer, threatening the balance of marine ecosystems. But there are other key factors that are negatively impacting the oceans and their inhabitants: marine pollution, especially from plastic. This poses a massive threat to marine life such as fish, dolphins and whales. Dr. Yuko Tajima from the National Museum of Nature and Science in Japan is therefore conducting nationwide stranding surveys to examine marine mammals that wash ashore. Her research has detected microplastics in stranded whales and dolphins, demonstrating how pollution spreads through the marine food web to large mammals.

Although no microplastics have been detected in blow samples from humpback whales in Miyakejima to date, the results of stranding investigations highlight a sobering reality: plastic pollution is reaching the top of the food chain and ultimately humans themselves. Recent studies have already detected microplastics in human blood.⁶ The long-term health consequences for humans have not yet been investigated sufficiently.