Thirteen species of seabirds are experiencing a strong population decline off the coast of south-eastern Australia, according to a new 17-year study released by the University of New South Wales.
Working with data collected by seabird enthusiasts of the Southern Ocean Seabird Study Association, who regularly take boat trips out to sea from Port Stephens, Sydney and Wollongong, the scientists found that almost half of the 30 most commonly observed seabird species in the region had declined over the 17-year period from 2000 to 2016.
“Seabirds are critically important organisms for maintaining the health of marine ecosystems,” says lead author and UNSW Science Honours student Simon Gorta.
“They act as apex predators, feeding on a range of prey such as plankton, squid, fish and carcasses across the world’s oceans.
“Our findings are worrying, not just because thirteen of our more common species are declining, but because we don’t know for sure what is driving these declines.”
While the exact reasons for the population decline are unknown, the researchers suggest that warming ocean temperatures are ‘likely to be contributing to this trend’.
“We can predict that as surface temperatures increase with climate change, we will be seeing fewer species that prefer cooler-than-average surface temperatures. The most dramatic example of this was in summer species – Pomarine and Arctic Jaegers - which showed this surface temperature preference and consistently declined in the region over the 17-year study period,” Mr Gorta says.
Worryingly, many other species may also be declining. This is supported by declines in breeding populations of seabirds, linked to a number of threats globally. The researchers say that determining the exact causes of these declines should be a priority.
“Seabirds are the most threatened group of birds on the planet, with roughly 30% of them listed on the IUCN Red List as at risk of extinction,” says co-author Professor Richard Kingsford, Director of the Centre for Ecosystem Science.