The research was published in Science (April 24 2020)
Abstract as follows:
Recent case studies showing substantial declines of insect abundances have raised alarm, but how widespread such patterns are remains unclear. We compiled data from 166 long-term surveys of insect assemblages across 1676 sites to investigate trends in insect abundances over time. Overall, we found considerable variation in trends even among adjacent sites but an average decline of terrestrial insect abundance by ~9% per decade and an increase of freshwater insect abundance by ~11% per decade. Both patterns were largely driven by strong trends in North America and some European regions. We found some associations with potential drivers (e.g., land-use drivers), and trends in protected areas tended to be weaker. Our findings provide a more nuanced view of spatiotemporal patterns of insect abundance trends than previously suggested.
A piece in ScienceAlert by Mike Mcrae, April 24 2020 gives an overview (extract as follows):
News of an insect apocalypse has become a familiar headline in recent years, with study after study pointing to an alarming loss in invertebrate numbers. As consistent as the message seems, the results don’t always agree with one another.
A new study led by ecologists from the German Centre for Integrative Biodiversity Research suggests the decline in global populations might not be as steep as we thought, and could actually be improving in some areas.
That conclusion might appear to be in stark contrast to claims we heard last year that 40 percent of all insect species face extinction, with some claiming an annual decline of 2.5 percent in their numbers worldwide, or even higher in some corners of the globe.
But taken in context, the new study builds a picture that shows how important it is to protect our environment and pay close attention to this vital part of the biosphere.
By compiling more than 160 surveys monitoring the weight of insect and arachnid populations around the globe, the researchers were able to get a good sense of the biomass and distributions of creepy crawlies dating as far back as 1925.
Their figures suggest there’s a marked difference in trends for invertebrates in different ecosystems in different parts of the world.