Insect biodiversity has declined by a third on some landscapes

Oct. 30 (UPI) -- The results of a new insect survey suggests insect biodiversity has declined by surprisingly large amounts over the last decade, even in forests and protected areas.

The new study isn't the first to look at the plight of insects. Several studies have shown insects to be negatively affected by land-use changes and climate change. One study in Germany found the biomass of flying insects declined by 75 percent across 63 nature reserves over a 30-year period.

But while other research efforts have focused on biomass or specific species groups -- moths or butterflies, for example -- the latest study, published Wednesday in the journal Nature, demonstrated an overall decline in insect biodiversity across an array of habitats.

Between 2008 and 2017, scientists in Germany collected 1 million insects at 300 test sites. Their data suggests at least 2,700 insect species have are in decline. By the end of the survey period, scientists measured a third fewer insect species present in forested areas and grasslands.

"Before our survey it was unclear whether and to what extent forests were affected by the insect decline as well," Sebastian Seibold, an ecologist at the Technical University of Munich, said in a news release.

Scientists measured declines in both biodiversity and biomass. The biomass of insects in forests declined by 40 percent over the 10-year survey, while insect biomass declined by roughly two-thirds in grasslands.

"A decline on that scale over a period of just 10 years came as a complete surprise to us -- it is frightening, but fits the picture presented in a growing number of studies," said Wolfgang Weisser, professor of terrestrial ecology at TUM.

While habitats closest to intensive farming operations featured the greatest declines in insect biodiversity and biomass, habitats of all kind were affected. Even unused forests in protected areas experienced declines in insect biodiversity of biomass. In protected forests, insects that travel the longest distances declined the most.

"To decide whether it is a matter of the more mobile forest-dwelling species having more contact with agriculture, or whether it has something to do with living conditions in the forests, further study will be needed," said Martin Gossner, a former TUM researcher.

Authors of the new study suggest current efforts to protect insects are too focused on singular plots of land. Researchers suggest a greater coordination between disparate conservation efforts is needed to boost the recovery of insect populations.