A heat wave causes a long-lasting population decline in a marine bird

It feels like many birds have become rare during the recent past. As a common reason for the diminishing populations climate change has been brought forward. However, conclusive evidence of this has been hard to find. Many people maintain that the temperature changes thus far observed cannot be causing diminishing bird populations. A recent study in Science (Renner et al., Science 386, 1272–1276 (2024) 13 December 2024) shows that marine heat wave of 2014-2016 in (Northern) Pacific caused the decline of Alaska’s common murre population to less than a half of what it was before the heat wave. What is almost more worrisome is that the populations have not shown any recovery in the years after the heat wave.

An important question thus rises. The year 2024 has exceeded all the temperature records – the 2014-2016 heat wave is small potatoes as compared to last year. Does this mean that the bird populations which have not recovered from the earlier heat wave will suffer another beating. If so, will the beating be serious enough to cause extinction of murre from many localities? That will be known in a couple of years.

The possibility that a heat wave causes significant excess mortality from which the populations do not recover even in more benign conditions is alarming. If that is the case, the local extinctions can occur already in conditions, where critical temperatures only occur sporadically. On the basis of the recently reported data this possibility must be taken seriously, further adding to the urgency of shifting away from fossil fuels.