New study suggests 75% decline of insect population over three decades

A new scientific study has found “alarming” and “dramatic” declines in insect populations around areas in Germany, which researchers said could have far-reaching consequences on global crop production and natural ecosystems.

The study, which was published in peer-reviewed journal PLOS One has found that in German nature reserves, flying insect populations have declined by over 75% over the duration of the 27-year study.

"The flying insect community as a whole... has been decimated over the last few decades," the study found, which was conducted by Researchers from Radboud University in the Netherlands and the Entomological Society Krefeld in Germany.

"Loss of insect diversity and abundance is expected to provoke cascading effects on food webs and to jeopardize ecosystem services."

Co-author Caspar Hallman said he and his colleagues were "very, very surprised" by the results.

"These are not agricultural areas, these are locations meant to preserve biodiversity, but still we see the insects slipping out of our hands," he said.

'This could be everywhere'

Entomologists have long had evidence of the decline of individual species, said Tanya Latty, a research and teaching fellow in entomology at Sydney University's School of Life and Environmental Sciences.

However, few studies have taken such a broad view of entire insect populations.

"This study lumps all flying insects together," she said, which gives researchers a more accurate picture of the overall decline.

"If you see these sort of dramatic declines in protected areas it makes me worry that this (trend) could be everywhere," she said.

"There's no reason to think this isn't happening everywhere."

The decline

The long-term study made use of Malaise traps - a sophisticated kind of insect net that catches a wide variety of insects - set up in 63 German nature protection areas over the course of 27 years.

By measuring the weight of the insect catch, the biomass, from each of the Malaise traps, researchers were able to ascertain the drop in insect numbers.

The study reported a seasonal decline of 76%, and mid-summer decline of 82% in flying insect biomass over the years.

"We show that this decline is apparent regardless of habitat type," the study says.

Latty says it's particularly worrying that the study recorded the declines in protected areas, meaning that for agricultural or urban areas the trend could be even more pronounced.

Latty says it's unlikely there's one "smoking gun," that is responsible for insect decline, but rather a combination of contributing factors. Climate change, loss of insect habitats and the use of pesticides have been suggested as potential causes.

The side effects

Species who rely on insects as their food source are likely to suffer from these declines.

Pollination of both crops and wild plants will also be affected, as is nutrient cycling in the soil.

"Ecosystem services provided by wild insects have been estimated at $57 billion annually in the USA," the study says, quoting an earlier study.

Some 80% of wild plants rely on insects for pollination; 60% of birds rely on insects as a food source, according to the study.

Latty says she hopes the decline is reversible.

"The first step is acknowledging that we have a problem, and working to correct that -- how do we design our agriculture to encourage insects? It could be something as simple as growing wildflowers along the edges of fields."

She says we also need to improve people's education around insect populations -- "that insects are important, absolutely crucial to our survival," and to deal with pests sensibly.

"There's so much going on out there, it's a struggle to convince people that insects are important. We've probably only identified only 10% of insects and some are going extinct before we can even name them."