Over the course of a decade, 7,000 whales died here. We finally know why

Based on 20 years of data, scientists found that a 20 percent decline in humpback whale numbers in the North Pacific coincided with a marine heatwave called a “bubble.” The event was responsible for record deaths among many bird species around the world, and has now been blamed for the deaths of nearly 7,000 humpback whales. Details are described in the magazine Royal Society Open Science.

Climate change has killed at least 7,000 whales, and that's not all

In the twentieth century, the number of humpback whales in the world increased (Megaptera novangelii) is threatened by commercial whaling. An estimated 31,865 of these marine animals were killed between 1900 and 1976, reducing their North Pacific numbers to approximately 1,200 to 1,600 individuals by the end of commercial fishing in 1976. They gradually recovered, but only until The entire planet is feeling the effects of the global crisis. Heating.

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Now scientists have used artificial intelligence for automatic image recognition created by Happywhale, a database of thousands of images of humpback whale tails from researchers and the public. In this way, 30,484 humpback whales were identified from 132,684 different encounters.

This data allowed us to calculate population changes over the past 20 years. A positive population recovery emerged in the years 2002-2012, with the number of individuals increasing at an average rate of 5.9%. annually. However, further analysis showed a significant decline between 2012 and 2021 as the number of whales decreased from approximately 33,488 to 26,662.

This coincided with the emergence of the “bubble” – a bubble of water in the Pacific Ocean linked to climate change. In 2013, when this anomaly was first discovered, ocean temperatures were 2.2-5.6^sC- Above average. Over time, the “bubble” grew to cover an ocean area of ​​4 million square kilometers²It extends from the Gulf of Alaska to Mexico.

The heatwave lasted for three years, causing toxic algal blooms, changes in the distribution of fish species, countless commercial fishing disasters and the deaths of marine life. In late 2016, cold conditions returned to the northeastern Pacific Ocean.

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Dr. Ted Cheeseman, co-founder and director of Happywhale, says:

Warmer water is less productive, such that a farm has fewer nutrients available to grow crops. Marine heatwaves kill organisms at the bottom of the food chain, creating a domino effect that reduces the availability of food for small and then large animals. Cetaceans expect to gain weight by eating krill, anchovies, herring, etc., but instead they starve.

Concerns about the stability of humpback whale populations continue to grow as climate change causes ocean temperatures to rise. Experts point out that the phenomenon we are witnessing today may become normal within 20 years. If this happens, a future heatwave could mean the oceans are truly uninhabitable.