Where have all the insects gone?

ABC News, 24 February 2018:

A global crash in insect populations has found its way to Australia, with entomologists across the country reporting lower than average numbers of wild insects.

University of Sydney entomologist Dr Cameron Webb said researchers around the world widely acknowledge that insect populations are in decline, but are at a loss to determine the cause.

"On one hand it might be the widespread use of insecticides, on the other hand it might be urbanisation and the fact that we're eliminating some of the plants where it's really critical that these insects complete their development," Dr Webb said.

"Add in to the mix climate change and sea level rise and it's incredibly difficult to predict exactly what it is."

Entomologist and owner of the Australian Insect Farm, near Innisfail in far north Queensland, Jack Hasenpusch is usually able to collect swarms of wild insects at this time of year.

"I've been wondering for the last few years why some of the insects have been dropping off and put it down to lack of rainfall," Mr Hasenpusch said.

"This year has really taken the cake with the lack of insects, it's left me dumbfounded, I can't figure out what's going on."

Mr Hasenpusch said entomologists he had spoken to from Sydney, Brisbane, Perth and even as far away as New Caledonia and Italy all had similar stories.....

The Guardian, 19 October 2017:

The abundance of flying insects has plunged by three-quarters over the past 25 years, according to a new study that has shocked scientists.

Insects are an integral part of life on Earth as both pollinators and prey for other wildlife and it was known that some species such as butterflies were declining. But the newly revealed scale of the losses to all insects has prompted warnings that the world is “on course for ecological Armageddon”, with profound impacts on human society.

The new data was gathered in nature reserves across Germany but has implications for all landscapes dominated by agriculture, the researchers said.

The cause of the huge decline is as yet unclear, although the destruction of wild areas and widespread use of pesticides are the most likely factors and climate change may play a role. The scientists were able to rule out weather and changes to landscape in the reserves as causes, but data on pesticide levels has not been collected.

“The fact that the number of flying insects is decreasing at such a high rate in such a large area is an alarming discovery,” said Hans de Kroon, at Radboud University in the Netherlands and who led the new research.

“Insects make up about two-thirds of all life on Earth [but] there has been some kind of horrific decline,” said Prof Dave Goulson of Sussex University, UK, and part of the team behind the new study. “We appear to be making vast tracts of land inhospitable to most forms of life, and are currently on course for ecological Armageddon. If we lose the insects then everything is going to collapse.”

The research, published in the journal Plos One, is based on the work of dozens of amateur entomologists across Germany who began using strictly standardised ways of collecting insects in 1989. Special tents called malaise traps were used to capture more than 1,500 samples of all flying insects at 63 different nature reserves.