Human activity causes dramatic falls in insects, which could see that 40% of the species are extinct in a few decades, a scientific study has warned.
The global review of the fall of insects warned that the world saw the world's largest extinction event on earth for millions of years, in view of habitat losses, pesticides, diseases and invasive species and climate change.
Because of the importance of insects for natural systems and other wildlife, "such events cannot be ignored and should hamper decisive measures to avert a catastrophic breakdown in the ecosystems of nature," the researchers warned.
The review, published in the journal Biological Conservation, examined 73 historical reports of insects from around the world, including studies in the UK, and found insects ranging from butterflies and bees to mildew were among the most affected.
Deviations affected not only specialized species, such as those relying on a particular host plant or living only in particular habitats, but also much more "generalist" species.
The researchers warned that the intensification of agriculture over the last six decades was "the cause of the problem" and that the relentless and widespread use of pesticides had a major impact.
The biggest driver of insect falls is the loss of habitat and the conversion of land to intensive agriculture and urban areas, followed by pollution, primarily by chemical pesticides and fertilizers.
Insects are also affected by biological factors such as pathogens and introduced species, and by climate change, where rising temperatures can affect the reach of places where they can live.
Insects are the key to functioning natural systems, from providing a food source to other wild animals such as birds, mammals, and amphibians, to pollinate plants and reuse nutrients.
The researchers Francisco Sanchez-Bayo and Kris Wyckhuys said: "The conclusion is clear: unless we change our ways of producing food, insects as a whole will go down the path of extinction in a few decades.
"The consequences this will have for the planet's ecosystems are catastrophic, to say the least, as insects are on the structural and functional basis of many of the world's ecosystems since their rise at the end of the Devonian period, nearly 400 million years ago."
They called for restoration of habitats, a dramatic reduction of pesticides and changes in agriculture to help insects like flowering strips planted along the edge of the fields or rotating crops with clovers for the benefit of hops.
Matt Shardlow, managing director of Wildlife Charity Buglife, said: "It is seriously cautious to see this collection of evidence showing the pitiful state of the world's insect populations.
"It is not just about bees, or even about pollinating and feeding ourselves, the fall also includes mildews that recycle waste and insects such as deciduous birds that start life in rivers and ponds.
"It is becoming increasingly clear that our planet ecology is collapsing and there is a need for an intense and global effort to stop and reverse these terrible trends – it is not a rational possibility that slow eradication of insect life continues."
He said insects accounted for more than half of the species on the ground, but the study showed that they disappeared much faster than birds and mammals.
"There is no single cause, but the evidence is clear. To stop this crisis, we urgently need to transform habitat fragmentation, prevent and mitigate climate change, clean up polluted water and replace pesticide dependence with more sustainable, ecologically sensitive agriculture".