A dramatic loss of at least 230 million seabirds over the past 60 years may represent a ‘canary in the coal mine’ with regards to marine ecosystems as a whole, a recent study reports. Research compiled on a sizable sample population from all of the world’s ecosystems found that seabird numbers plummeted by an astonishing 70% between 1950 and 2010. While the exact cause of this decline is unclear, ecologists suspect that the introduction of ‘factory trawlers’ fishing widely in the open oceans may have something to do with it.
‘The level of decline is considerably greater than what we were expecting,’ says co-author Dr. Edd Hammill of the University of Technology, Sydney. The species most heavily affected are those that migrate globally, relying on locations that have fewer and smaller fish to eat. ‘As they are moving across the planet, if any one of the places they visited has been impacted then they’re much more likely to decline.’
Such a drastic reduction in the seabird population is likely to affect a wide range of other species, both on land and at sea, as the birds function as ‘mobile links’ between marine and terrestrial ecosystems, transferring nutrients from one location to another by eating fish at sea and then releasing their waste on land.
Recently published in the journal PLOS ONE, the study was the first to focus on the entire globe, treating every species as equal rather than picking out a handful to follow. The researchers compiled a database of global seabird population records and used modeling to estimate the overall population trend. Hammill says 230 million is a conservative estimate, noting that a ‘back-of-the-envelope’ calculation suggests a loss of over a billion birds during the period of study.
‘Human activities such as fisheries and pollution are threatening the world’s marine ecosystems, causing changes to species abundance and distribution that alter ecosystem structure, function and resilience,’ explained the study authors.
‘In response, increasing numbers of marine biologists and managers seek to achieve management measures allowing the persistence of healthy, productive and resilient ecosystems. Such ecosystem-based management requires better understanding of ecosystems pre-disturbance, as baselines of harvested and/or otherwise impacted species such as fish, marine mammals, and seabirds have shifted from their historical levels.’
Other studies, such as this one from the Stockholm Resilience Centre, suggest that food quality is just as important as quantity when it comes to sustaining seabird populations in locations like the Baltic Sea.