Insect populations around the world are in a dramatic decline over 30 years – whereas water-based insects are not so.
A team of scientists from around the world recently analysed 166 long-term survey of insects from 1,676 sites worldwide and used their data to track populations of insects going as far back as 1925. Urban sprawl with expanding towns were deemed a major factor in the decline in land-dwelling insects.
In contrast, some water base insects increased by more than a third in populations the reason put down to environmentally friendly water policies protecting habitats.
Lead author Dr Roel van Kink, from the German Centre for Integrative Biodiversit Research, said butterflies, grasshoppers and other land insects had declined steadily for the past 75 years shown by 50 per cent fewer over the 75 years. On that basis, that would mean 24 per cent fewer insects in 30 years’ time.
‘Insect declines happen in a quiet way and we don’t take notice from one year to the next,’ the insect specialist added.
‘It’s like going back to the place where you grew up. It’s only because you haven’t been there for years that you suddenly realise how much has changed, and all too often not for the better.’
The researchers claim their findings confirm the so-called ‘windscreen phenomenon’ – that fewer bugs get splatted on their windscreens than 30 or 40 years ago.
Professor Jonathan Chase, from iDiv, another author on the paper, said: ‘Many insects can fly, and it’s those that get smashed by car windshields.
Declines were strongest in some parts of the US and in Europe, which saw its biggest drops year on year since 2005, particularly in Germany.
Meanwhile, studies of insects that live part of their lives under water, like midges and mayflies, showed an average increase of 1.08 per cent each year.
That works out at a 38 per cent leap over 30 years for water-based insects. The scientists saw that as optimism for land dwelling insects.
The researchers say the trend is promising evidence that it’s not too late to reverse man-made effects on insects.