By Clara Lincolnhol
Climate change is making it easier for Great Lakes water birds to get sick, according to a recent University of Illinois study.
The study identified avian diseases in the Great Lakes, including botulism and avian influenza, that could be primed for outbreaks amid warming waters and shifting migration patterns.
Data from the last 50 years shows an increase in avian disease as climate change worsens, said study co-author Nathan Alexander. The U.S. Fish and Wildlife Service has noted an increase in disease risk while monitoring avian populations, he said.
For example, warming waters have contributed to increased cases of botulism among waterbirds, Alexander said. Botulism is caused by a toxin produced by a specific type of bacteria under the right environmental conditions. It kills fish and birds that ingest the toxin by paralyzing and weakening their muscles and causing difficulty standing, flying and breathing.
Botulism toxins are often produced where cladophora algae sits atop water in large mats and decomposes. The algae produces more botulism toxins when water is warmer, said Alexander, a postdoctoral research associate at the University of Illinois.
Water levels also play a role in algae growth and toxin production.
“The water level impacts how and where the algae grows as well as the concentration of the nutrient runoff from developed areas or agricultural areas,” Alexander said.
Great Lakes water levels are also “wrapped up in climate change” as the region sees changes in precipitation and more variable water patterns, he said.
“Hard rains might increase runoff from agricultural areas that can increase nitrogen loading and thus increase algae production,” Alexander said.
Changing habitat and increased risks
Climate change could also lead to more outbreaks of contagious illnesses like bird flu, salmonella, duck plague and Newcastle disease. Warmer temperatures and new ice patterns are shifting migration habits and home ranges, leading to new chances for bird-to bird transmissions, he said.
“Where species are moving more, they’re establishing new areas,” Alexander said. “And every time that happens there’s a potential risk of an infected individual doing that and introducing the disease to a new area.”
Warmer temperatures mean birds arrive sooner and stay longer at their summer breeding grounds. Dense bird populations on waterways and earlier arrivals create more opportunities for disease exposure and spread, Alexander said.
“This also poses risks as more severe weather earlier in the year along with earlier arrival times may impact nesting success and survival, posing risks particularly to endangered species populations,” he said.
Many migratory birds’ winter ranges are changing because winters are milder, said Barb Avers, waterfowl and wetland specialist at the Michigan Department of Natural Resources.
Historic wintering grounds see fewer birds as they no longer have to travel as far south. Birds don’t need to migrate if they can access unfrozen water and food. Some do a lot of bouncing back and forth as ponds freeze and thaw, she said.
In Michigan, for instance, the Canada goose population has grown, with many year-round residents.This makes catch and relocation methods ineffective and unsafe. Introducing potentially ill geese to a new area puts other geese at risk. This is why the Michigan DNR has changed their Canada goose management program to allow euthanasia with a permit, Avers said.
What people can do
The current bird flu outbreak in the U.S. that has caused egg prices to sky rocket is widespread among wild bird populations, according to the Center for Disease Control. Currently, 70 bird-to-human cases have been reported. There are currently no reported human-to-human cases, but bird flu is highly contagious for house cats.
Biodiversity loss due to bird illness is dangerous for a healthy ecosystem, Alexander said. Biodiversity creates resilient, stable ecosystems where complex interactions like nutrient cycling and toxin filtration can successfully take place. You don’t want an ecosystem to cave in on itself, he said.
Birders should document the species they see in the Great Lakes using apps like iNaturalist. Recording sightings is helpful for scientists to then extrapolate environmental relationships, Alexander said.
An understanding of climate change and accessible public data is essential for combatting these problems, especially in the context of the current historic avian flu outbreak, he said.