If you're old enough you may remember to have to wipe the squished remains of moths, grasshoppers and other insects from your windscreen while driving through regional Australia.
According to Francisco Sanchez-Bayo, that's a great Australian tradition gone.
"When I started doing studies, we had to stop every time we filled up the petrol to clean the windscreen, because it was full of moths and crickets and insects of all kinds. Now there are none," he said.
It's anecdotal evidence, but it's backed up by a first global review of insect reporter studies across the world and the reasons for it, undertaken by Dr. Sanchez-Bayo, a honourary associate at the University of Sydney and published recently in Biological Conservation.
"Among those, a third of all the species goes into extinction, they are in danger right now. The rate of extinction in insects is about eight times higher than the rate of extinction of the vertebrates."
Dr. Sanchez-Bayo and his colleague Kris Whyckhuys analyzed all the long-term studies of insect populations they could find. The majority of the 73 studies were from Western Europe and the United States, with only a handful of studies from other parts of the world and only one from Australia.
One study, in Germany, saw a 75 per cent decline in insect biomass over 27 years. Another study in Puerto Rico reported losses of between 78 and 98 percent over 36 years.
The rates of decline are so dramatic – up to 2.5 percent a year – that Dr Sanchez-Bayo claims that in current rates there may be no insects in those regions within 10 years.
Losses were reported across all insect groups, although some species were increasing in number, he said.
"The ones that are going to be extinct are specialist species, which require very specific conditions to live on," Dr Sanchez-Bayo said.
Insect decline claims 'not backed up'
That's why Manu Saunders, a research fellow in ecosystem services, believes that claims of catastrophic decline by Dr Sanchez-Bayo are overstated.
"It's a significant wake-up call that insect populations are changing in some places."
"But to claim worldwide decline of all insects is not backed up by what data is actually available."
Many insect species on Earth have not been described yet, so we do not know anything about them – where they live, how they live, what their life cycle is, what impacts them.
"A lot of insects could be affected worse, or they could not be as bad, but the point is that we do not actually know," said Dr Saunders.
In Australia, most of our native insect species have not yet been identified. The only study suitable to be included in Dr Sanchez-Bayo's analysis was on commercial honey bees in Queensland.
So what's causing declines?
There were many different causes for declines in the reviewed studies.
However, Dr. Sanchez-Bayo found that there were four significant factors: habitat loss; pollution, especially pesticides and fertilizers; biological factors, including pathogens and introduced species; and climate change.
The dramatic loss of insect biomass in Puerto Rico was largely attributed to climate change, with strong correlation with the frequency of severe cyclones and subsequent forest destruction.
In Germany, the reduction in insects was attributed to the introduction and increasing use of systemic pesticides, applied as a prophylactic against insect pests.
"If you live in tropics, it's most likely to be deforestation and climate change [that are responsible for declining insect populations], but in Europe – where deforestation is no longer a problem – it's the use of chemical fertilizers and pesticides, and the reduction of other elements that used to be present in the agricultural landscape, such as hedge rows, trees, flowers, weeds. "
However, Dr. Saunders points out that we can not necessarily extrapolate the information to Australia, or other areas not covered by the review.
"It's OK to speculate that these drivers are likely to have the same impact in areas where we do not have data, but we can not say that unequivocally."
When the insects go, the animals go
Dr. Sanchez-Bayo is aware that his claims are dramatic, but believes it's important to draw attention to this issue.
"We try to ring the alarm bells very loudly so everyone listens," he said.
Besides all the important functions that insects play in our ecosystems – such as pollination, or recycling nutrients – they are also essential element in the food chain that supports life on our planet. When the insects go, the frogs, birds and mammals do not have food.