Saturday, June 17, 2017

Midges Making Climate

Mücken machen Klima was the title of an article in the Badische Zeitung about the Büschelmücke. When I looked up the equivalent in the English Wikipedia I read: The Chaoboridae, commonly known as phantom midges or glassworms, are a family of fairly common midges with a cosmopolitan distribution.

Why would a midge influence climate, even if there are billions of them? What I did not read in Wikipedia were recent results of a research by teams of the Universities of Geneva, Swansea and Potsdam. The scientists confirmed that during two years the larvae of Chaoboridae live in muddy pools and ponds preferring eutrophic waters where they will reach densities of up to 130,000 larvae per square meter. They feed on waterflies, springtails, and other mini beasties but only during night hours. During the day the larvae hide from their predators by diving up to 70 meters deep into the muddy bottom of the water.

Chaoborida larva or glassworm (©Wikipedia)
Long before submarines were developed Chaoboridae larvae used the technique of submersion. The research showed that while waiting on the bottom for the sunset the "glassworms" start to fill their ballast tanks with methane until they will drift to the surface. Here they stabilize in their hunting position. At dawn the larvae release all methane until they sink to the bottom again. It is all a question of energy as the scientists calculated. Even if the larvae catch four waterflies in 24 hours they would need 80 % of the gained energy to dive by mechanical means. The submersion technique is an evolutionary success for Chaoboridae but seems to be a catastrophe for the climate.

Büschelmücke (Chaoborida). Note the Büschel (tufts) (©Wikipedia)
The scientists attribute nearly 8 % of the total global methane emission to the midges in particular as they release additional methane when stirring up the mud in the process of grounding. With the melting of permafrost in Arctic regions captured methane is not only released "naturally" but the formation of water puddles will enlarge the Lebensraum (habitat) of the Büschelmücke, i.e., there is more muddy water to place their eggs. So Chaoboridae will actively amplify the "natural" release of methane due to rising temperatures in the Arctic. As for animals only cows contribute more methane on a global scale (27 %) than the midges.

Shall the community sponsor further research on Chaoboridae? Here on the Upper Rhine Freiburg's authorities are instead quarrelling about the financing of a campaign against the tiger mosquito. It came in lorries from the south of Europe and hibernated in our region. So globalization paired with climate change is stimulating the Asian mosquito to move farther north spreading angst about new diseases.

Tiger mosquito (©dpa)
In Freiburg's north an allotment garden is infested with tiger mosquitos: There are lots of nests and many of the larvae are hatched, an expert said, their next leg would be Freiburg's central cemetery with all its watering pots, a situation that would make the spread of the tiger mosquito run out of control.

Why do the Freiburg authorities hesitate to spend 50,000 euros? Well, fighting the tiger mosquito with a chemical mace would result in collateral damage to other insects, but who likes to see the birds starve? In fact, a recent census in Freiburg has shown that the population of birds within the city boundaries has dramatically decreased over the last years, a trend due to a more and more restricted habitat for birds in combination with less food.

Another circulus vitiosus.

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