Clouds of emerging mayflies were once a regular sight on English summer evenings and they are a key part of the food chain that supports fish, birds and mammals. But modest levels of pollution found in many English rivers are having a devastating impact on mayflies, new research suggests, killing about 80% of all eggs. In October, a study found that the abundance of flying insects has plunged by 75% in 25 years, prompting warnings that the world is “on course for ecological Armageddon”, with profound impacts on human society.
Paul Knight, chief executive of Salmon and Trout Conservation (STC), which is conducting an in-depth three-year survey of rivers, said: “The results of this groundbreaking new study are irrefutable. We believe this is just the tip of the iceberg. Lose your invertebrates and other species will follow.”
The new research looked at the blue-winged olive, a common mayfly present across the British Isles and most of continental Europe. Its numbers have fallen significantly in recent decades and it has almost vanished from some English rivers.
“The young life stages are the most vulnerable, just as with human babies,” said Nick Everall, at the Aquascience Consultancy and who led the research published in the journal Environmental Pollution. Blue-winged olive eggs are laid on river beds and then have to survive for up to eight months over winter before hatching into nymphs. “Mayflies such as the blue-winged olive are a crucial component in the aquatic food chain but numbers have declined substantially in many UK rivers over the past 30 years, particularly in chalk streams,” said Everall, whose study was supported by STC. “Their continuing loss can affect the survival of other important species such as wild fish, bird life and mammals,” he said.
Source: The Guardian, 11 Jan 2018