By Jeremy Hance, The Guardian, September 22, 2015
|Arctic tern (Sterna paradisaea)|
Every day for sixty million years, seabirds have performed mind-boggling acts of derring-do: circumnavigating the globe without rest, diving more than 200 meters in treacherous seas for a bite of lunch, braving the most unpredictable weather on the planet as if it were just another Tuesday and finding their way home in waters with few, if any, landmarks.
But now seabirds, like so many other species, may have met their match.
Conservationists have long known that many seabird populations are in decline, but a recent paper in PLOS ONE finds the situation worse than anticipated. According to the researchers, seabird abundance has dropped 69.7% in just 60 years – representing the deaths of some 230 million animals.
“I was very surprised with the result, it was considerably greater than I’d expected,” said Edd Hammill, co-author of the paper, with Utah State University. “What we should take away from this is that something is serious amiss in the oceans.”Ben Lascelles, a Senior Marine Officer with Birdlife International, who was not involved in the study, said he found the research alarming because the decline appeared practically indiscriminate, hitting a “large number of species across a number of families.”
Seabirds, which include any bird that depends largely on the marine environment, comprise nearly 350 species worldwide – an astonishing variety of extreme-loving birds. For example, the indefatigable wandering albatross, which sports the largest wingspan on the planet; the child-sized Emperor penguin, the only bird that breeds during the Antarctic winter; and the tiny storm petrel that practically capers on the water as it feeds – they are named for St. Peter after all.
But, given that seabirds inhabit both the open ocean and the shoreline, this eclectic mix of birds faces a litany of threats: overfishing, drowning in fishing lines or nets, plastic pollution, invasive species like rats in nesting areas, oil and gas development and toxic pollution moving up the food chain. And as if these weren’t enough, the double-whammy of climate change and ocean acidification threatens to flood nesting sites and disrupt food sources.
“Seabirds are particularly good indicators of the health of marine ecosystems,” explained lead author, Michelle Paleczny with the University of British Columbia and the Sea Around Us Project. “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.”
But with such a large number of species across such a wide variety of environment one is left asking: how did the scientists count so many birds?
First, the team of researchers scoured all the population data on seabirds available. They found demographic data on 3,213 populations. But they couldn’t use all of theses counts, since conservationists had surveyed many of these far-flung populations just once or twice – not enough to show a real trend.
The team eventually selected 513 populations that had been counted at least five times. In all, these populations represented about 19 percent of the world’s seabirds.
Still, Hammil said he believes the team’s findings “are an accurate representation of what is happening worldwide.”
He added, “although we did not include every population, all seabird families were included, and we included populations from every major coastline in the world.”
Paleczny also said that when the researchers looked at the differences between monitored and unmonitored populations, they saw “no evidence that the monitored populations are declining more.”
“The trends for many seabird species have clearly been downwards for a number of years, and this paper provides further evidence of this,” Lascelles said.
Still, Paleczny and Hammil’s research arguably paints an even more alarming picture of the state of the world’s seabirds. For example, according to them, the tern family has fallen by 85%, frigatebirds by 81%, petrels and shearwaters by 79%, and albatrosses by 69%.
Such dismal findings point to one of the study’s patterns: open ocean birds – such as albatrosses, frigatebirds, petrels and shearwaters – are generally faring worse than birds that stick near the coasts.
“[Open-ocean] seabirds are hit especially hard due to their large geographic ranges. Because these species travel so far, there is a greater chance they will encounter threats,” said Hammill who noted that coastal birds “in some cases” are doing better because of improved management of breeding areas and improved fishing gear.
But even when threats were minimised, Lascelles noted that recovery requires diligence and patience.