Every year 17 million people cross the Pyrenees to migrate

About 17 million insects fly across the Pyrenees every year, traveling along Puerto de BujarueloIt is a 30-meter-wide crossing located on the border between France and Spain. Over the past 4 years, this clearly noticeable phenomenon – which appears as a huge, dark swarm accompanied by a low, deep hum – has been observed and studied by a team of scientists from Britain’s University of Exeter.

Using video cameras and butterfly nets, the researchers recorded the flow of flies, wasps, butterflies and dragonflies through the corridor each autumn on their way from northern regions, including the UK, to locations in southern Europe and North Africa where winters are milder. Dr Carl Wootton, from the Center for Ecology and Conservation at Exeter, who led the research, said: “Seeing so many insects moving purposefully in the same direction at the same time is truly one of nature’s great wonders.”

The origin of the work goes back to the discovery made in 1950 by British ornithologists Elizabeth and David Lack, who came across a bird sighting. Migration through the pass located at an altitude of 2273 metres. “They witnessed – recalls Will Hawkes, from the Center for Ecology and Conservation at the University of Exeter, quoted by the Guardian – a large number of migratory hoverflies passing through the mountains. We went to the same pass to check whether this migration still took place and record the number and species involved.” “Not only were large numbers of hoverflies still migrating through the passage, but also other insects, from flies to dragonflies: On some days, the number exceeds 3,000 meters per minute“.

However, the number of insects has declined alarmingly around the world, and the number crossing the passage is thought to have declined since the Lacks first noticed the phenomenon, although numbers were not recorded in an accurate manner until 70 years ago. The Exeter team hopes their findings will spur determination to protect their habitats.