The 2014–2016 Pacific marine heatwave caused the largest documented vertebrate die-off linked to warming oceans.
Over four million common murres (Uria aalge) in Alaska, more than half the population, were wiped out.
The common murre or common guillemot is a large auk.
It has a circumpolar distribution, occurring in low-Arctic and boreal waters in the North Atlantic and North Pacific.
It spends most of its time at sea, only coming to land to breed on rocky cliff shores or islands.
This study highlights a swift (one year) and intense (50% population loss) impact of climate change on marine birds, unlike previously documented gradual changes over years or decades.
The findings establish a direct and immediate link between marine heatwaves and mass mortality in seabird populations.
Characteristics and Effects of Marine Heatwaves
Defined as intense, prolonged, and expansive ocean warming events, marine heatwaves are increasingly frequent due to climate change.
Consequences include:
Mass mortality of habitat-forming species like kelps and corals.
Cascading trophic effects, leading to altered ecosystem productivity.
Displacement of lower-trophic-level species, amplifying food shortages for top predators.
Impacts on Marine Ecosystems
Top predators like seabirds face:
Reduced reproductive success.
Increased mortality rates.
Mass die-offs.
Broader population-level impacts, however, are less understood, making this study crucial.
The decline signals a possible new threshold of response to global warming, with upper trophic predators like murres unable to sustain historical population sizes.
This event may reflect a diminished capacity of marine ecosystems to support seabird populations under the stress of warming oceans.
The study underscores the urgency of addressing global warming to mitigate marine heatwaves and protect marine biodiversity.
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