Van Klink et al. 2020 have examined trends in insect abundance around the world and have shown that terrestrial insects are in desperate long-term decline, but that insect populations in rivers in countries with strong water pollution laws have been recovering in recent years.
This is the first study to show that, on balance, insect abundance is in steep decline worldwide - 0.92% per year which translates to an average loss of 8.81% per decade. Studies using other methods (including direct measurement) have produced insect population decline figures of between 2.2 and 2.7% per year. If these steep declines are not addressed then there will be further damage to ecosystems and their ability to support crops and life on Earth.
Many insect species are threatened with extinction because the area in which they can survive is shrinking, often partly due to climate change, however trends in the distributions of species were excluded from this study which only looked at abundance and biomass trends.
The report also looked at freshwater invertebrate biomass and abundance and found the average trend is for an 11% increase per decade. This seems to be a genuine good news story. The 2019 UK State of Nature reported a long and steep decline going back to at least the 1970s, followed by a significant reversal of that decline since 1995. Recent improvements in freshwater invertebrate abundance are thought to be the result of strong and effective modern water pollution legislation in the EU and North America, that has reduced sewage and industrial contamination in rivers. Most aquatic insect abundance data is from rivers, trends in populations associated with ponds and ditches are rarely studied.
Freshwater represents only 2.4% of the Earth’s terrestrial surface, and few of its inhabitants are pollinators, so the massive decline in the abundance of flying insects, recorded particularly in Central Europe, remains a developing ecological disaster. The study identifies land use change as a key factor, particularly the process of urbanisation, which has a stronger relationship with declines than might be expected; perhaps caused by associated light pollution and other pollution. Trends were slightly less negative, but still negative, near crops and on protected areas such as nature reserves.
Read more in this article from Buglife for CJS: No Insectinction
Insects are in decline scream the harsh headlines from countless reports and studies from across the world, some even predict 41% of insect species could be extinct by 2050 without urgent action now. Against this backdrop Buglife have launched the No Insectinction Campaign calling on global decision makers to reverse the declines through a series of measures. All of which we can also implement ourselves to a small degree to be part of the necessary global change.