Marine heat wave caused seabird deaths off California. El Nino could worsen die-off

A massive marine heat wave off the California coast has led to widespread seabird deaths, raising concerns among scientists and conservationists. The situation has escalated dramatically, with reports indicating that many seabirds, including California brown pelicans, loons, and grebes, have perished due to starvation. These deaths are attributed to the disruption of marine ecosystems caused by unusually high ocean temperatures. Marine ornithologist Tammy Russell, a postdoctoral scholar at the University of California, San Diego, Scripps Institution of Oceanography, described the scene she encountered while surveying a San Diego beach, where she found numerous seabird carcasses scattered among washed-up kelp and under rocks. The phenomenon has become increasingly alarming, as it marks a grim assessment of the ongoing environmental stress on local wildlife.

The marine heat wave, which has persisted for several months, has significantly impacted the availability of nutrients essential for marine life. Record-setting ocean temperatures have reduced the presence of cold, nutrient-rich surface water where krill, anchovies, and sardines typically thrive. As a result, these critical food sources for seabirds have become scarce, leading to mass starvation. Russell noted that some seabirds, such as cormorants, have died shortly after reaching the shore, with instances of death occurring within mere minutes. Such occurrences are unprecedented and have left her deeply distressed. The die-off is not isolated to specific species; it appears to be affecting a wide range of seabirds across the entire coastline.

The potential exacerbation of this crisis is linked to the formation of El Niño, a natural climatic phenomenon characterized by the warming of the central and eastern equatorial Pacific Ocean. Scientists warn that the current El Niño, which has already begun to take shape, could intensify, leading to higher global temperatures and potentially worsening the existing marine heat wave. According to the U.S. National Oceanic and Atmospheric Administration, the El Niño is expected to grow to historic strength, possibly extending into 2027. This development poses a significant threat to marine ecosystems, as it could further disrupt food webs and threaten the survival of various species, from gray whales to seabirds.

Historically, die-offs of seabirds have occurred periodically, but experts suggest that such events are becoming more frequent due to the ongoing effects of climate change. The persistence of the marine heat wave, which has lasted for over a year, represents only the third instance on record of such an extended period of elevated coastal water temperatures. Daily ocean temperature measurements conducted by Scripps Institution of Oceanography reveal that three of its ten coastal monitoring stations broke records for sustained periods of warmth, highlighting the severity of the current situation. Robotic underwater gliders equipped with sensors have also documented high temperatures offshore and at greater depths, drawing comparisons to the conditions experienced during the last El Niño event in 2023.

The implications of these findings extend beyond immediate ecological concerns. Wildlife rehabilitation facilities have reported treating hundreds of emaciated seabirds this spring, underscoring the urgency of the issue. J.D. Bergeron, CEO of International Bird Rescue, emphasized that while it is not uncommon to find dead birds on beaches, the sheer number of deceased seabirds is highly unusual. Brown pelicans, in particular, have been observed seeking food in unconventional locations, sometimes resulting in injuries from fishing gear. These observations highlight the broader disruptions in marine ecosystems and the cascading effects of climate-related changes on both marine and terrestrial environments. As the situation continues to evolve, the scientific community remains vigilant, anticipating further challenges and striving to mitigate the impacts of these environmental shifts.