The world's monitored seabird populations have dramatically declined by 70 per cent since the 1950s, a stark indication that marine ecosystems are not doing well, a new study has warned.
Researchers compiled information on more than 500 seabird populations from around the world, representing 19 per cent of the global seabird population.
They found overall populations had declined by 69.6 per cent, equivalent to a loss of about 230 million birds in 60 years.
"Seabirds are particularly good indicators of the health of marine ecosystems," said Michelle Paleczny, a University of British Columbia master's student.
"When we see this magnitude of seabird decline, we can see there is something wrong with marine ecosystems. It gives us an idea of the overall impact we're having," said Paleczny.
The dramatic decline is caused by a variety of factors including overfishing of the fish seabirds rely on for food, birds getting tangled in fishing gear, plastic and oil pollution, introduction of non-native predators to seabird colonies, destruction and changes to seabird habitat, and environmental and ecological changes caused by climate change.
Seabirds tend to travel the world's oceans foraging for food over their long lifetimes, and return to the same colonies to breed.
Colony population numbers provide information to scientists about the health of the oceans the birds call home.
Albatross, an iconic marine bird that lives for several decades, were part of the study and showed substantial declines. Paleczny said these birds live so long and range so far that they encounter many dangers in their travels.
A major threat to albatross is getting caught on longline fishing hooks and drowning, a problem that kills hundreds of thousands of seabirds every year.
"Our work demonstrates the strong need for increased seabird conservation effort internationally," said Paleczny.
"Loss of seabirds causes a variety of impacts in coastal and marine ecosystems," said Paleczny.
Seabirds play an important role in those ecosystems. They eat and are eaten by a variety of other marine species. They also transport nutrients in their waste back to the coastal ecosystems in which they breed, helping to fertilise entire food webs.
The study was published in the journal PLOS ONE.