Bird-shat cools Arctic

Guano ammonia from millions of birds promotes cloud formation

Puffins breed in large colonies at the shores of the Arctic Ocean and North Atlantic © ATGImages / thinkstock
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Surprising cooling effect: Arctic seabirds have more influence on the climate than expected. Because their huge breeding colonies produce large quantities of guano and this releases ammonia. This in turn promotes the formation of aerosols in the atmosphere of the far north. By this effect, the seabirds cause a small, but measurable cooling of the Arctic climate, as researchers in the journal Nature Communications "report.

The Arctic is the region of the world where climate change is most noticeable. The sea ice is melting, permafrost is thawing and temperatures are rising faster than anywhere else. Arctic wildlife needs to adapt accordingly, including millions of seabirds breeding each year in the far north.

Guano as a gas spinner

But these feathered Arctic visitors are not just passive Arctic climatic objects, as Betty Croft from Dalhousie University in Halifax and her colleagues have now discovered. Instead, the seabird colonies also exert a measurable impact on the climate.

For their study, researchers first measured ammonia levels near bird colonies in the Canadian Arctic. The gas is released when bacteria decompose the guano of the birds. At the same time, ammonia is considered to be an important factor in the formation of aerosols and clouds in the atmosphere. Whether the ammonia from the Guano of Arctic birds is sufficient to achieve such an effect, the researchers have checked by their measurements on site and by climate models.

Change in cloud germ density due to bird droppings ammonia (a) and cooling effect caused by aerosols (b) © Croft et al., Nature Communications / CC-by-sa 4.0

Up to 50 percent more aerosols

The surprising result: The colonies of the seagulls actually release so much ammonia that they increase the NH3 content of the atmosphere north of the 66th degree of latitude by more than 50 percent. In the summer, the values ​​near the breeding grounds can even increase by up to 500 percent, as the researchers report. display

Further investigations revealed that the gas forms aerosols in the air that are large enough to affect cloud formation. "The number of particles larger than 80 nanometers increased in the near-surface air area by 10 to 50 percent of, especially near large seabird colonies, " said the researchers. The highest concentrations were found for the eastern coast of Greenland and the archipelago of the Canadian Arctic.

Guillemots (Uria aalge) form particularly dense breeding colonies - correspondingly much guano and ammonia are produced. Duncan Wright / CC-by-sa 3.0

Measurably less sunshine

But is all this enough to influence the sun's rays and thus the Arctic climate? To find out, the scientists entered the determined values ​​in a climate-atmosphere model. And in fact: The additional suspended matter causes a small but measurable cooling effect on a regional level. The ammonia-promoted cloud formation reduces the solar energy input by 0.5 to 1 watt per square meter, as the researchers report.

"I never dreamed that sea birds could make such a substantial contribution to the climate, " says Wentworth. The guano of millions of young birds helps to cool off their habitat at least a little bit. However, this climate effect is not even sufficient to compensate for anthropogenic warming or significantly buffer it. It shows, however, that the climate of our planet is linked in many and sometimes unexpected ways with its inhabitants. (Nature Communications, 2016; doi: 10.1038 / ncomms13444)

(Nature Communications, 18.11.2016 - NPO)