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Home / australia / Insect population and species decline and 'wake-up call', scientists say – Science News

Insect population and species decline and 'wake-up call', scientists say – Science News

If you're old enough, you may have to wipe squished remains of moths, grasshoppers and other insects from your windscreen when driving through regional Australia.

key points insects

Key points:

  • Scientists looked at 73 longitudinal studies of insect populations from around the world
  • In average, 41% of known insect species in the studies were in population decline
  • Losses were reported across all insect groups, but some species were increasing in number

According to Francisco Sanchez-Bayo that's a great Australian tradition gone.

"When I started doing the studies we had to stop every time we filled the oil to clean the windscreen, because it was full of moths and crickets and insects of all sorts, and now there are none," he said.

It is anecdotal evidence, but it is backed by the first global review of the study of insect decline across the world and the reasons for it, conducted by Dr Sanchez-Bayo, a Honorary Associate at the University of Sydney and published recently in Biological Conservation.

"Among those, a third of all species are going 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 vertebrates."

Dr Sanchez-Bayo and his colleague Kris Whyckhuys analyzed all the long-term studies of insect populations they could find. Most of the 73 studies were from Western Europe and the US, with only a handful of studies from other parts of the world and only one from Australia.

One study, in Germany, saw a 75 percent decline in insect biomass over 27 years. Another study in Puerto Rico reported losses between 78 and 98 percent over 36 years.

The rates of decline are so dramatic – up to 2.5 percent per year – that Dr Sanchez-Bayo claims that at 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.

"Those who are going to be extinct are the specialist species, which requires very specific conditions to live on," Dr Sanchez-Bayo said.

Insect declines claims 'not backed up'

That's why Manu Saunders, a research fellow in ecosystem services, believes that the claims of catastrophic decline made by Dr Sanchez-Bayo are overstated.

"It's an important wake-up call that insect populations are changing in some places."

"But to claim the 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 their impact.

"A lot of insects could be affected worse, or they could not be as bad, but the point is that we do not really know," said Dr Saunders.

In Australia, most of our native insect species have not yet been identified. The only study to be included in Dr Sanchez-Bayo's analysis was on commercial honey bees in Queensland.

So what's causing declines?

There have been many different causes for declines in 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 a 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 the tropics, it's 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 is 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 effect in areas where we have no 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 is 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 an 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.

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