Seabird populations declined 70 percent throughout the modern industrial era

8/20/2015 | 0

Magnificent Frigatebird in Puerto Morelos, Mexico, by Harry Collins.

Magnificent Frigatebird in Puerto Morelos, Mexico, by Harry Collins.

Pelagic birding trips and guides may be more sophisticated than ever, and birders on boats may be recording new species every year, but the sad truth is that the number of seabirds living today is only a fraction of what existed decades ago.

According to research published online early this summer, the world’s monitored seabird populations declined 70 percent between 1950 and 2010. The drop is equivalent to a loss of about 230 million birds.

Researchers Michelle Paleczny, Edd Hammill, and others analyzed a database containing population sizes for about 19 percent of the world’s seabirds and 13 of the 14 seabird families.

Of them, three increased, while the other 10 decreased, some dramatically. Procellariidae (petrels and shearwaters) and Phalacrocoracidae (cormorants) fell by over 70 percent, while both Sternidae (terns) and Fregatidae (frigatebirds) decreased by more than 80 percent.

A substantial proportion of the overall loss was due to large declines in the five most abundant populations, all of which were in the Southern Hemisphere. In 1950, they accounted for over 30 percent of seabirds sampled, but by 2010 each had been reduced to less than 5 percent of its initial size.

Introduced species, entanglement in fishing gear, overfishing, climate change, plastic and oil pollution, habitat disturbance, development, and direct exploitation were among the factors that likely caused the declines, write the researchers.

“While seabird conservation efforts have been successful in reducing mortality of some species in recent decades, for example, banning some direct exploitation, eradicating some introduced predators, reducing some entanglement in fishing gear, these efforts are evidently not sufficient in terms of stopping or reversing large-scale seabird decline, especially as new threats emerge, notably industrial harvesting to food.”

The results demonstrate a need for increased international conservation. “The removal of cats and rats from small islands has been achieved on multiple occasions and been shown to increase local seabird numbers,” write the researchers. “However, undertaking conservation actions for pan-global populations, such as reducing oceanic pollution or lowering fishing pressure, will be considerably more challenging.”

The study was a contribution of the Sea Around Us Project, a scientific collaboration between the University of British Columbia and the Pew Charitable Trusts.

A version of this article appeared in the October 2015 issue of BirdWatching.

Read the paper

Michelle Paleczny, Edd Hammill, Vasiliki Karpouzi, and Daniel Pauly. 2015. Population Trend of the World’s Monitored Seabirds, 1950-2010. PLoS ONE 10(6): e0129342. doi:10.1371/journal.pone.0129342

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