Additionally, when insects die, they return nutrients to the earth; insects are at the bottom of the food chain, with many small animals relying on insects as food; and some insects help with pest control, according to a National Geographicinterview with author David MacNeal.
"Our work reveals dramatic rates of decline that may lead to the extinction of 40 per cent of the world's insect species over the next few decades", researchers wrote.
The study, to be published in the journal Biological Conservation, pulled together data from more than 70 datasets from across the globe, some dating back more than a century.
But insects comprise about two-thirds of all terrestrial species, and have been the foundation of key ecosystems since emerging nearly 400 million years ago.
In addition to the 40% at risk of dying out, a third of species are endangered - numbers that could cause the collapse of the planet's ecosystems with a devastating impact on life on Earth.
Unless we change our ways of producing food, insects as a whole will go down the path of extinction in a few decades.
Author of the review, Dr Francisco Sanchez-Bayo, an honorary associate with the Sydney Institute of Agriculture in the School of Life and Environmental Sciences, said that habitat loss from intensive agriculture alongside agro-chemical pollutants, invasive species and climate change are the main drivers behind the collapse in insect populations. Pollution, particularly the heavy use of pesticides and fertilizers, is also a major contributor to the dwindling number of insects around the world. The researchers also note this is the first study of its kind to provide a global picture of insect decline. With many species of birds, reptiles and fish depending on insects as their main food source, it's likely that these species may also be wiped out as a result. "It's quite plausible that we might end up with plagues of small numbers of pest insects, but we will lose all the wonderful ones that we want, like bees and hoverflies and butterflies and dung beetles that do a great job of disposing of animal waste".
Matt Shardlow, chief executive of wildlife charity Buglife, added: "It is gravely sobering to see this collation of evidence that demonstrates the pitiful state of the world's insect populations".
They suggested overhauling existing agricultural methods, "in particular a serious reduction in pesticide usage and its substitution with more sustainable, ecologically-based practices".