Seabirds are today’s canaries in the coal mine – and they’re sending us an urgent message

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David Schoeman, University of the Sunshine Coast; Brian Allan Hoover, Chapman University, and William Sydeman, University of California San DiegoJust as caged canaries once warned coal miners of the risk of carbon monoxide poisoning, free-flying seabirds are now warning humanity about the deteriorating health of our oceans.

Seabirds journey vast distances across Earth’s seascapes to find food and to breed. This exposes them to changes in ocean conditions, climate and food webs. This means their biology, particularly their breeding successes, can reveal these changes to us on a rare, planet-wide scale.

We collated and analysed the world’s largest database on seabird breeding. Our findings reveal a key message: urgency in the Northern Hemisphere and opportunity in the south.

The Northern Hemisphere ocean systems are degraded and urgently need better management and restoration. Damage to Southern Hemisphere oceans from threats such as climate change and industrial fishing is accelerating, but opportunities remain there to avoid the worst.

Seabird breeding success is a good indicator of ocean health.
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Oceans at a crossroads

Seabirds often travel far across the planet. For example, many sooty shearwaters breed in New Zealand, yet travel each year to the productive waters of the northeast Pacific. Arctic terns migrate even further, travelling each year between the Arctic and Antarctic.

Scientists often use satellite-derived data sets to determine, for example, how the oceans’ surfaces are warming or how ocean food webs are changing. Few such data sets span the globe, however, and this is where seabirds come in.

Over its long journey, a seabird eats fish and plankton. In doing so, it absorbs signals about ocean conditions, including the effects of pollution, marine heatwaves, ocean warming and other ecological changes.

Seabird breeding productivity (the number of chicks produced per female per year) depends on the food resources available. In this way, seabirds are sentinels of change in marine ecosystems. They can tell us which parts of oceans are healthy enough to support their breeding and which parts may be in trouble.

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Many sooty shearwaters breed in New Zealand then migrate to the northeast Pacific.
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Deciphering seabird messages

In some cases, seabirds tell us directly about major distress in the oceans. This was the case in 2015-16, when around a million emaciated common murres died, many washing up on beaches from California to Alaska. The seabirds experienced severe food shortages caused by an acute marine heatwave.

In other cases, seabird health can hint at longer-term and more subtle disruption of ocean ecosystems, and we are left to decipher these messages.

In this task, seabird breeding provides important clues about marine food webs that are otherwise difficult or impossible to measure directly, especially at global scales. Thankfully, seabird scientists around the world have consistently measured breeding productivity over decades.

Our research team included 36 of these scientists. We collated a database of breeding productivity for 66 seabird species from 46 sites around the world, from 1964 to 2018. We used the data to determine whether seabirds were producing relatively more or fewer chicks over the past 50 years, and whether the risk of breeding failure was increasing or decreasing.

In the Southern Hemisphere, there’s still time to reverse the oceans’ plight.
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Striking findings

In the Northern Hemisphere, breeding productivity of plankton-eating birds such as storm petrels and auklets increased strongly over 50 years, but breeding productivity of fish-eating birds declined sharply.

In the Southern Hemisphere, by contrast, breeding productivity of plankton-eating seabirds declined weakly, but increased strongly for fish eaters.

In short, fish-eating seabirds in the north are in trouble. Decreasing breeding productivity leads to population declines, and the low breeding rate of seabirds (many species only have one chick per year) means populations recover slowly.

More worrying, though, were our findings on the risk of breeding failure.

In the Southern Hemisphere, the probability of breeding failure was low throughout the study period. The same was true for Northern Hemisphere plankton feeders. But fish eaters in the north showed dramatically increasing risk of breeding failure, most acutely in the years since 2000.

Importantly, increasing risk of breeding failure was also much higher for seabirds that feed at the ocean’s surface, such as black-legged kittiwakes, compared with those that feed at greater depths, such as puffins.

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Risk of breeding failure was higher for seabirds that feed at the ocean’s surface.
©Eric J Woehler

What this tells us

Unfortunately, these results match what we know about human-caused damage to the ocean.

First, many pollutants such as plastics collect close to the ocean surface. They are often eaten by surface-feeding seabirds, potentially hampering their ability to produce chicks.

Similarly, the rate of ocean warming has been more than three times faster, and the change in number of marine heatwave days twice as large, on average, in the Northern than Southern Hemisphere over the past 50 years.

Likewise, northern oceans have sustained industrial fisheries for far longer than those in the south. This has likely reduced food supplies to Northern Hemisphere fish-eating seabirds over longer periods, causing chronic disruptions in their breeding success.

But human impacts in the Southern Hemisphere are accelerating. Ocean warming and marine heatwaves are becoming more intense, and industrial fisheries and plastic pollution are ever-more pervasive.

Rate of warming of the surface ocean over the past 50 years.

We must heed the warnings from our seabird “canaries”. With careful planning and marine reserves that take account of projected climate change, the Southern Hemisphere might avoid the worst consequences of human activity. But without action, some seabird species may be lost and ocean food webs damaged.

In the Northern Hemisphere, there is no time to waste. Innovative management and restoration plans are urgently needed to avoid further deterioration in ocean health.

This story is part of Oceans 21

Watch for new articles ahead of the COP26 climate conference in Glasgow in November. Brought to you by The Conversation’s international network.

David Schoeman, Professor of Global-Change Ecology, University of the Sunshine Coast; Brian Allan Hoover, Postdoctoral Fellow, Chapman University, and William Sydeman, Adjunct associate, University of California San Diego

This article is republished from The Conversation under a Creative Commons license. Read the original article.

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Plastic poses biggest threat to seabirds in New Zealand waters, where more breed than elsewhere

The Northern Royal Albatross is one of many species of seabird that breed in New Zealand.
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Stephanie B. Borrelle, Auckland University of Technology

Plastic pollution has the potential to cause the worst damage to seabirds in the seas around Aotearoa New Zealand, where many of them come to feed and breed.

Aotearoa boasts the greatest diversity of seabirds in the world. Of the 360 global seabird species, 86 breed here and 37 are endemic, which means they breed nowhere else.

Some 90% of New Zealand’s seabirds are threatened with extinction. They (and many other marine species) are under pressure from pollution, climate change, and overexploitation of marine resources. Plastic pollution could be the final nail in the coffin for many seabirds that are already struggling for survival.

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An international plastics treaty could avert a ‘Silent Spring’ for our seas

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Plastic – not so fantastic

Every week, another grotesque story illustrates the impact of plastic in the environment. A whale was recently found with 80 plastic bags in its stomach – it died, of course.

One-third of marine turtles have died or become ill due to plastic ingestion in Aotearoa New Zealand.

A 2015 study suggested that 99% of seabirds would be ingesting plastic by 2050. The authors also predicted that seabirds in our backyard, the Tasman Sea (Te Tai o Rēhua) would be the hardest hit, because of the high densities of seabirds foraging in the region, and the overlap with plastic. This not that surprising, given that the earliest observations of Aotearoa’s seabirds ingesting plastic go back to 1958.

The Chatham Island albatross feeds in the Southern Ocean and breeds only on The Pyramid, a large rock stack in the Chatham Islands, New Zealand.
Stephanie Borrelle, CC BY-SA

Sentinels of ocean plastic pollution

Seabirds are particularly vulnerable to ingesting plastics because most species feed at or near the ocean surface. They forage along eddies and oceanic convergence zones – the same areas where marine plastics accumulate. The impacts of plastic on seabirds and other marine wildlife include death by entanglement. Ingested plastic can inhibit a bird’s feeding capacity, leading to starvation or internal ulcers, and eventually death.

Flesh-footed shearwater populations in Aotearoa may have declined up to 50% to around 12,000 pairs since the 1980s, and have gone extinct at some of their Hauraki Gulf breeding sites. These declines continue in spite of predator eradication and an end to harvesting on many of the islands where they breed.

Autopsies of birds caught in fisheries in Aotearoa’s waters show flesh-footed and sooty shearwaters are more likely to contain plastic fragments than other species. Plastic fragments found in New Zealand flesh-footed shearwater colonies showed a linear relationship between the number of nest burrows and plastic fragments, indicating that plastic ingestion may be a driver in their population decline.

Toxic plastic soup

In Australia, up to 100% of flesh-footed shearwater fledglings contained plastic, the highest reported for any marine vertebrate. Fledglings with high levels of ingested plastic exhibited reduced body condition and increased contaminant loads.

The chemical structure of plastics means that they act as toxin sponges, attracting harmful contaminants from the surrounding seawater, including persistent organic pollutants and heavy metals. When an animal ingests plastic, there is the potential for those toxic chemicals to leach into its tissues.

Chemicals such as PCBs and flame retardants that are added to plastics during manufacture have been found in seabird tissue around the Pacific. High concentrations of toxic chemicals can retard growth, reduce reproductive fitness and, ultimately, kill.

Sooty shearwater (tītī) chicks, which are harvested and consumed by Māori in Aotearoa, have a high potential for ingesting plastic, given evidence of plastic ingestion in shearwaters from Australia and anecdotal evidence from harvesters on Stewart Island (Rakiura). The closely related short-tailed shearwater, which breeds in Australia, has also been show to consume plastic. In one study, 96% of chicks contained plastics in their stomachs and chemical loads in their tissue.

Ocean health and human health

Few, if any, studies have specifically looked at contaminant loads derived from plastics in any species of seabird in Aotearoa. However, Elizabeth Bell from Wildlife Management International is now collecting samples of preen glands, fat and liver tissue for analysis of toxic chemicals in bycatch birds found with plastic inside them. This research is crucial to understanding the implications of the transfer of toxins to people from harvested species that ingest plastic.

Seabirds are the sentinels of ocean health. They tell us what we can’t always see about the health of the oceans and its resources that we rely on.

Plastics are sold to us on the perceived benefits of strength, durability and inexpensive production. These qualities are now choking our oceans.

In a few decades, we have produced an estimated 8.3 billion tonnes. The expedited pace of production has not been met with adequate waste management and recycling capacity to deal with it all. As a result, an estimated 8 million tonnes of plastic pollute the environment each year.

Global production of plastics is doubling every 11 years. It is predicted to be an order of magnitude greater than current production levels by 2040. The time is ripe for the initiation of an international agreement to lessen plastic pollution in the world’s oceans and save our seabirds and marine wildlife.

Stephanie B. Borrelle, Conservation Ecologist, Auckland University of Technology

This article was originally published on The Conversation. Read the original article.