Heatwave Causes Devastating Loss of Seabirds in Alaska

The common murre, a large black-and-white seabird native to northern waters, has become significantly less common in Alaska over the past decade due to the effects of climate change.

A recent study published in Science reveals that an unprecedented marine heat wave in the northeast Pacific from 2014 to 2016 led to a massive population decline, killing about four million birds—half of the species in the region. Alarmingly, there has been little sign of recovery, suggesting long-term changes in the food web that have forced the ecosystem into a troubling new state.

Heather Renner, lead author from the Alaska Maritime National Wildlife Refuge, explained that while many species are declining due to temperature changes, this event was unique as it wasn't a gradual decline but a catastrophic event. Renner and her colleagues highlighted that this could be the largest recorded mortality event of any wildlife species in modern history.

The findings raise serious concerns, particularly as human-caused climate change makes such heat waves more frequent, intense, and prolonged.

The common murres, often called the "penguins of the north" due to their tuxedo-like appearance, are expert divers with slender wings that help them travel great distances for food. However, they were unprepared for the environmental disaster triggered by the marine heat wave, which began in late 2014 and affected the northeast Pacific Ocean from California to Alaska. Over two years, it caused widespread devastation, including the deaths of 62,000 starving murres along the Pacific coast.

Experts attribute the deaths to two main factors: higher ocean temperatures, which reduced the quantity and quality of phytoplankton (a primary food source for fish like herring, sardines, and anchovies), and warmer waters, which increased the energy demands of larger fish like salmon and Pacific cod, that also compete with murres for food.

Renner explained that while the event was recognized as a major issue at the time, it was difficult to measure its full effects. Initially, the death toll was estimated to be about one million, but after a more detailed analysis of data from 13 murre colonies, researchers found that the true number of deaths was four times higher.

While the marine heat wave caused significant damage to many species, it didn't affect all animals equally. For example, thick-billed murres, which share nesting cliffs with the common murres, appeared largely unaffected, possibly due to their more adaptable diet. However, the common murres have yet to recover, and the losses may be irreversible, partly due to the long-term decline of their prey and their reliance on large colonies for protection from predators.

Despite the grim situation, Renner remains hopeful. While tackling global warming is crucial for addressing long-term climate change, conservation efforts in the short term, such as removing invasive species like foxes and rats from murre nesting islands, could offer the species a chance to recover.