Guillemots, black and white birds each measuring about a foot tall, cram together on Skomer Island to starve off predators and protect their eggs, of which each reproducing bird lays just one each year. On this island off the coast of Wales, nearly 100,000 of these seabirds once huddled in groups next to neighboring puffins, but the population was nearly killed off due to oil pollution and tanker traffic starting in World War II. After hitting a nadir of 2,500 in 1972, the guillemot population made a miraculous comeback over several decades, reaching 30,000 in 2022.
Then, in the summer of 2023, bird flu hit Skomer Island, killing about 15,000 birds, said Timothy Birkhead, a professor at the University of Sheffield who has spent the past 50 years studying the population. These deaths will be felt throughout the ecosystem.
"The guillemot is a key player in the Skomer 12-species seabird community,” Birkhead told Salon in an email.
The current bird flu panzootic — or a pandemic in animals — has spilled over to an unprecedented number of animals across the world since it began in 2020, killing off elephant seals, cougars, polar bears, and dozens of other mammalian species. Millions of wild birds have died from H5N1, the virus that causes bird flu, and more than 13 million poultry and 900 dairy herds have been impacted in the U.S. while at least 66 human cases have been reported. The first U.S. death from bird flu was reported last week in a patient from Louisiana.
Every infection brings us closer to another pandemic like COVID-19, experts have emphasized. A big question is why is the crisis growing now? H5N1 has been documented since the mid-'90s, with scientists warning for decades that the virus had pandemic potential. Part of what's making it such an issue today might be related to climate change.
"Climate change can affect those large scale patterns, like migration, that could bring birds into contact with agricultural systems."
Although it’s difficult to pinpoint a direct cause-and-effect relationship between climate change and bird flu, research going back many years before the current crisis linked our heating world and natural disasters with changing migratory patterns, nesting seasons, and habitat ranges of wild birds. All of this is influencing the way avian flu spreads across the world.
“Climate change is unpredictable because we can talk about a global increase in temperature, but that doesn't mean it's necessarily going to get warmer everywhere," said Dr. Damien Joly, a wildlife biologist at the University of Saskatchewan in Canada. “But what we do know is that climate change can affect those large scale patterns, like migration, that could bring birds into contact with agricultural systems that they have not been in contact with before.”
Avian flu outbreaks date back centuries, when it was once known as "fowl plague," but this outbreak is unique. This time, the virus is adapting to the environment in new ways, infecting a record number of species and surviving various seasons without dying out, Joly said.
Clinical waste bags containing the carcasses of deceased birds await removal from Staple Island off the coast of Northumberland, where the impact of Avian Influenza (bird flu) is having a devastating effect on one of the UK's best known and important seabird colonies. (Owen Humphreys/PA Images via Getty Images)“When you think of any virus system, there are really three components that affect whether that pathogen will persist,” Joly told Salon in a phone interview. “There are host effects, pathogen effects, and the environment. Changes in the relationship between those three groups is what leads to changes in disease dynamics."
One of the ways a changing climate can impact bird flu is by increasing numbers of extreme weather events. Bird flu first arrived in North America in 2014, following a typhoon in Asia that impacted the North American Pacific Flyway, one of the major avian superhighways. In 2021, the arrival of the current outbreak in North America also coincided with windstorms in the North Atlantic that were happening at the time, said Dr. Claire Teitelbaum, who studies wildlife and infectious diseases at the USGS Georgia Cooperative Fish and Wildlife Research Unit and is also a professor at the University of Georgia.
“Those events definitely affect when and where animals are,” Teitelbaum told Salon in a phone interview. “Animals in general are pretty good about moving away from natural disasters but they can also take those diseases they have with them as they move.”
Extreme weather events could also displace bird habitats, change the way they access food, and consequently impact the way that species can fend off a virus, said Dr. Erin Sorrell, a virologist and a senior scholar at the Johns Hopkins Center for Health Security.
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On Skomer Island, the guillemot population may have been made extra vulnerable to the virus due to a food shortage that occurred just before bird flu struck, likely caused by a major storm and the highest sea temperatures in the region ever on record that impacted the availability of food sources.
“All of these things can kind of come together to create a perfect storm, or you might only need three out of five of those factors to be able to have an opportunity for the virus to be around just a little bit longer, to expose one more bird species that is migrating or one more bird species that is in the surrounding environment,” Sorrel told Salon in a phone interview.
Additionally, warmer temperatures have shifted migration patterns for some species earlier, which means certain birds are spending more time on their breeding grounds, Teitelbaum said.
“From the avian flu perspective, that is important because breeding grounds can be places of high transmission,” Teitelbaum said.
One 2019 case study looking at how bird flu infected the avian population in Qinghai Lake in China reported that the wild birds there encountered the virus at their wintering grounds and traveled across Eurasia and into Egypt and Northern Africa, said the study’s author Dr. Barbara Canavan.
“It started in Qinghai,” Canavan told Salon in a phone interview. “It is a place that is warming very fast and where they’ve had significant changes in farming, providing a viral pathway to get to birds that are far more mobile."
At least 70% of pathogens that infect humans come from wildlife, and as the human population continues to expand to every corner of the globe, it increases the chances that some of those pathogens will spill over to infect people. Ultimately, the environmental alterations humans have made, like developing farmland underneath one of the greatest migratory bird flyways, serve to provide avian influenza with a consistent source of hosts. For example, bird flu was detected in pigs for first time late last year.
“In poultry populations, when you are constantly introducing new susceptible individuals, it allows these viruses to persist," Joly said. "They can’t burn themselves out when you are constantly adding fuel to the fire.”
The Centers for Disease Control and Prevention (CDC) maintains that the risk to the general population of being infected with bird flu is low, although farmworkers in the dairy and poultry industry are at greater risk. Still, the virus is increasingly spilling over to other animals, including humans. The major concern is that the more chances bird flu has to transmit between hosts, the greater the risk that it could evolve to become more dangerous. This could occur if an infected host is also infected with another virus and genetic material is swapped in a process called viral reassortment.
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“All of these impacts that climate change could have on locations and species interactions or temperatures in the environment are all likely to impact the rate at which the virus evolves,” Teitelbaum said. “Because it would impact when and where different genotypes of the virus are in the same place and in the same bird and able to do that reassortment.”
Surveilling how the virus transmits in the environment among wild birds can help protect domestic species and reduce its spread. In May, the U.S. Department of Agriculture received $824 million to fund the surveillance of wild birds in addition to mitigating the spread of bird flu in agriculture. Thus far, the agency has already funneled more than $2 billion in combating the virus on farms. But some are calling for additional funding to go toward the surveillance of wild birds in order to get ahead of the virus.
“Ultimately, it’s way cheaper to fund the surveillance of wildlife populations for diseases than it is to try and deal with the millions of chickens that have died associated with avian influenza in this continent," Joly said. “Being able to go upstream and detect and figure out mitigation before it gets into humans … is ultimately so much cheaper and more effective because you are not chasing your tail.”
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