A long-term study of humpback whale populations in the North Pacific Ocean shows that climate change is having a negative impact on the species.
Marine biologist Joëlle De Weerdt of the VUB, founder of the non-profit organization ELI-S and co-author of the study, explains: ’Humpback whales have large, distinctive pectoral fins and a melodious song. They are often seen close to the coast and are known for their impressive leaps. They also migrate every year between feeding and breeding grounds. Indeed, whales find their main sources of food - krill and sardines - in cold waters, but give birth to calves in warmer waters. ’
Scientific research on humpback whales only began in the 1970s, and has focused mainly on population dynamics, repopulation mechanisms and why some populations do better than others. The new study, led by Ted Cheeseman of Australia’s Southern Cross University, relies on AI recognition software (https://happywhale.com/) to recognize individual photos of tails. ’’It’s a kind of facial recognition software for whales,’’ says Joëlle De Weerdt. ’ After gathering data from humpback whale populations throughout the North Pacific, we have the largest identification dataset ever created for a whale species,’ notes Ted Cheeseman. Our results show a significant repopulation of the population following the end of commercial whaling in 1976. Indeed, the estimated number of individuals rose from 17,000 in 2002 to 33,500 in 2012. However, a worrying trend has emerged in recent years: the population has recorded an apparent decline of 20% between 2012 and 2021 (a drop of around 7,000 individuals). This suggests that the population has abruptly reached its carrying capacity due to the decline in prey ’, adds Ted Cheeseman.
The consequences of climate change appear to have played a significant role in the observed population decline. The study reveals that the strongest marine heatwave ever recorded on a global scale that occurred in 2014-2016 has had lasting repercussions on the repopulation of the species.
This research is a wake-up call to try and better understand the interaction between marine ecosystems and climate change", notes Ted Cheeseman. They underline the urgency of effective conservation efforts to protect this and other iconic species from the consequences of climate change. ’
The study was published under the following reference :
Cheeseman Ted al. 2024 ’ Bellwethers of change: population modelling of North Pacific humpback whales from 2002 through 2021 reveals shift from recovery to climate response ’. R. Soc. Open Sci.11: 231462. https://doi.org/10.1098/rsos.231462
Contact : Joelle De Weerdt : joelle.de.weerdt@vub.be, +32 (0)497712087
