Sea Level Rise and Storm Wave Flooding Threaten Seabirds

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Islands used by tropical seabirds are highly vulnerable to sea level rise according to a new study released today.

Image:  Black-footed Albatross with Chick
Black-footed albatross with chick, nesting black-footed albatrosses are especially vulnerable to sea-level rise and sudden flooding on low-lying islands.Location: Midway Atoll National Wildlife RefugePublic domain

ISLAND OF HAWAI‘I, Hawaii — Islands used by tropical seabirds are highly vulnerable to sea level rise according to a new study released today. Many seabird species have disappeared from human-populated islands and their worldwide distributions are now concentrated on low-lying islands protected as wildlife refuges and marine national monuments.

Led by the U.S. Geological Survey, the study showed that Laysan albatrosses, black-footed albatrosses and Bonin petrels are especially susceptible to repeated nest losses from sudden flooding events expected to increase in frequency and magnitude with sea level rise and storm surge.

“Our study illustrates that sea-level rise threats will affect low-lying Pacific Islands earlier than previously expected,” said seabird ecologist Karen Courtot of the USGS. “Restoring seabird colonies at higher elevations provides alternatives for species most vulnerable to overwash events before nests are perpetually flooded.”

To understand how climate change may impact islands and their biodiversity, scientists modeled sea level rise combined with storm surge at an important seabird breeding colony on Midway Atoll in the subtropical Pacific Ocean. An analysis of habitat and seabird traits revealed that albatrosses and Bonin petrels were especially exposed to sudden flooding when the rising sea is combined with winter storm waves.

Researchers measured the average elevation of three islands that make up Midway Atoll at 3.2 meters or less and mapped flooding on these islands using various sea level rise scenarios at 0.5 meter, 1 meter, 1.5 meters, and 2 meters. A scenario using 2 meters sea level rise, compounded by ground water inundation and storm waves, could cause the displacement of more than 616,400 breeding albatrosses and Bonin petrels. Approximately 60 percent of the albatrosses and 40 percent of the Bonin petrels’ nests were flooded.

Map with the location of the Hawaiian Islands and the Northwestern Hawaiian Islands.
Map with the location of the Hawaiian Islands with the Northwestern Hawaiian Islands circled.

More than 95 percent of the global breeding populations of Laysan albatrosses, black-footed albatrosses and Bonin petrels are restricted to breeding in the low-lying northwestern Hawaiian Islands. Their egg-laying and chick-rearing occurs when storm waves are most likely to strike.     

“A surprising result to many is that some of the most locally abundant species like albatrosses and Bonin petrels were actually the most sensitive to sea level rise impacts,” said Michelle Reynolds, lead author of the USGS-led study.

In the Hawaiian Islands, invasive predators prevent the establishment of seabird breeding colonies at higher elevations and remain a threat to nesting seabirds.

The journal article “Will the Effects of Sea-Level Rise Create Ecological Traps for Pacific Island Seabirds?” was published today in PLOS ONE with lead author Michelle Reynolds and her USGS co-authors Karen Courtot and Curt Storlazzi, and Paul Berkowitz of Hawaii Cooperative Study Unit at the University of Hawaii at Hilo, Janet Moore of Saint Mary’s University, Halifax, and Elizabeth Flint of U.S. Fish and Wildlife Service.  

Image: Laysan Albatross and Bonin Petrel Chick
Laysan albatross and Bonin petrel chick, two seabird species especially vulnerable to sea-level rise and sudden flooding on low-lying islands.Location: Midway Atoll National Wildlife Refuge Public domain
Image: Boinin Petrel Chick
Boinin petrel chick, a subterranean nesting seabird especially vulnerable to sea-level rise.Location: Midway Atoll National Wildlife RefugePublic domain