Sea birds are “guardians” of marine health. When marine ecosystems suffer, birds will be among the first to show it.
Now a major study finds that seabirds in the northern hemisphere are already having problems. And without extra precautions, those in the southern hemisphere could be next.
The results indicate broader patterns of environmental change in the world’s oceans. Climate change combined with pollution, overfishing and other human activities are constantly changing the food webs in the sea. Food sources shift. Some fish populations are dwindling or migrating to new areas.
As a result, seafaring birds, which sit at the top of the food chain, struggle to breed and raise their young. They are, so to speak, canaries in the coal mine – clear signs that something is wrong with the entire ecosystem.
“Seabirds travel long distances – some go from one hemisphere to another – and hunt for food in the ocean,” said P. Dee Boersma, a biologist at the University of Washington and one of the study’s authors, in a statement. “This makes them very sensitive to changes in things like ocean productivity, often over a large area.”
The new study published in the journal yesterday scienceexamines data on 66 seabird species worldwide for 50 years. The study, led by William Sydeman of the Farallon Institute in California, included contributions from more than three dozen experts to institutions around the world.
The study shows that many species do not breed as successfully as in the past – especially in the northern hemisphere. They produce and raise fewer chicks.
The researchers studied a wide variety of birds, including species that feed primarily on plankton, species that prefer fish, and species that eat both. Birds that partially or exclusively eat fish were found to be the most vulnerable.
In addition, birds that feed primarily on the surface of the ocean were more prone to breeding failure than deep-diving birds.
It’s no surprise that these problems are more severe in the northern hemisphere, the researchers say. In the northern half of the world, the oceans are warming faster. Other human influences such as shipping and fishing are more pronounced in the northern hemisphere.
Together, these threats have likely had a greater impact on marine ecosystems in the north. Studies have already shown that certain fish populations are declining or moving to different parts of the ocean. Even plankton populations change over time.
These changes can put seabirds in a difficult position.
Seabirds often return to the same coastal locations year after year to breed and raise their chicks. During the breeding season, they make excursions between the sea and the land, looking for food, and then returning to feed their babies. When their food sources sink or move, it can become more difficult for them to feed themselves and successfully raise their young.
The fact that fish-eating birds are most vulnerable on the surface is a telling detail, said Sydeman, the lead author, in an interview with E&E News. It indicates that the upper part of the ocean is changing most dramatically.
“The signs are that this part of the ocean’s productivity is declining, and the birds give us a window into that change,” he said.
The study does not analyze exactly which human influences are to blame most. The researchers performed some additional analysis which found that rising sea temperatures are closely related to the breeding success of the seabirds.
Still, it is likely that the combination of climate change and other human influences put such a strain on the birds.
But the study doesn’t necessarily mean a disaster – at least not yet. Seabirds are usually long-lived, resilient animals, Sydeman said. They can withstand temporary food shortages and bounce back after a year or two with little breeding success.
“The problem is when it becomes chronic,” said Sydeman. “And this study suggests that it becomes a chronic problem for the northern hemisphere.”
This means that intervention may – and soon – be appropriate to prevent more dramatic declines in the future.
This could mean focused efforts to reduce fisheries in areas near seabird breeding colonies and to build up fisheries on which birds rely heavily for food. In the southern hemisphere, the establishment of larger marine protected areas could help keep fisheries stable and healthy.
Meanwhile, global efforts to reduce greenhouse gas emissions and curb climate change are required to slow the rate of ocean warming.
All over the world, seabirds are sending “a red flag that we really need to think about this now before it gets too bad,” said Sydeman. “For most species, there is still time to avert disaster.”
Reprinted from E&E News with permission from POLITICO, LLC. Copyright 2021. E&E News provides important news for energy and environmental professionals.