3.5 Trillion insects migrate over southern England skies every year

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As many as 3.5 trillion insects are said to be migrating over the southern England skies annually, a new study by researchers at University of Exeter and Rothamsted Research has revealed.

The study, published in the journal Science, involved use of specialised radar techniques to capture the movement of insects over the skies in that particular region. Researchers point out that while their study hasn’t been able to find out the origin and destination of each of the insects, there is a strong possibility – based on previous studies – that many of these insects will have been travelling to and from the UK over the English Channel and North Sea.

Scientists point out that previous radar studies have only measured migrations of relatively few nocturnal species of agricultural pests and there has been no study that looked into vast numbers of daytime migrants. The latest study differs substantially from previous ones because it looked into daytime species.

In the latest study, scientists recorded movement above radar sites in southern England and found large seasonal differences, with mass migrations of insects generally going northwards in spring and southwards in autumn. While there were seasonal variations from year to year, the overall the net northward spring movements of larger insects were almost exactly cancelled out by net southward movements in autumn over the 10-year research period.

The study focused on insects flying more than 150 metres above the ground, using radar for larger insects (10mg and over) and netting samples for smaller ones.

If we look at the movement in quantitative terms from a different perspective, the movement of insects amounts a whopping 3,200 tons of biomass, or more than seven times the mass of the 30 million songbirds which depart the UK for Africa each autumn; or equivalent of about 20,000 flying reindeer.

“Animal migration, especially in insects, is a very complex behaviour which takes millions of year to evolve and is very sensitive to climatic condition,” said co-author Dr Ka S (Jason) Lim, of the Radar Entomology Unit of the AgroEcology Department at Rothamsted Research. “Global climatic change could cause decline of many species, but equally other highly adaptable species thrive and become agricultural crop pests.”

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