Plants and Animals

Vast Annual Migration Of Insects Across The UK Recorded At High Altitude

Every year in the skies above the United Kingdom, there is a vast migration that very few know about, and for the first time, researchers have been able to track it. A throng of high altitude flying insects goes on the move every year, involving trillions of bugs as they move from the UK over to the warmer continent. 

According to the researchers, to give it a festive spin, this is equivalent to 20,000 high-flying reindeer.  

It turns out that every year an estimated 3.5 trillion insects migrate over the UK, but at such a high altitude, it happens without most people noticing. In fact, so great are these numbers, that the biomass of these movements is seven times greater than that of the 30 million songbirds that leave the shores of Britain for their annual migration to Africa.

“If the densities observed over southern UK are extrapolated to the airspace above all continental landmasses, high-altitude insect migration represents the most important annual animal movement in ecosystems on land, comparable to the most significant oceanic migrations,” explained Dr Jason Chapman, from the University of Exeter, who co-authored the study published in Science. “Insect bodies are rich in nutrients and the importance of these movements is underappreciated.”

The researchers found the insects generally moved across the English Channel and the North Sea to the continent in autumn, and then returned back in the springtime. But despite the vast numbers of creatures involved, and their huge importance, little has been done to investigate the exact scale of the movements. The insects are vital in maintaining the ecosystems across northern Europe, as well as being essential in the agricultural sector.

The majority of the insects that go on the move are small bugs such as crop aphids and midges, but among this cohort are much larger creatures, ranging in size from ladybirds to butterflies. Some of the insects travel massive distances and at some speed for the little creatures they are. The researchers measured speeds of 36-58 kilometers per hour (22-36 miles) over distances of up to 300 kilometers (186 miles).

What’s more, the migration is a considered affair. The insects will fly up into high altitude, and then assess the wind direction and speed before setting off, which suggests that the insects have some form of inbuilt compass. This is much more complex behavior for such small animals than anyone had really thought existed before.

The size of the migration, and any changes in it over the coming years, could be used as an indication to how climate change is impacting the ecosystems and environments.

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