Over 75% loss of insect biomass and scientists don’t know why

Insect article image
Image: poppy via Flickr

Over the past decade the decline of particularly delicate insects, such as honeybees and butterflies, has generated a lot of buzz and for good reason. In the U.S. alone the number of beehives has declined by 60% over the past half-century. While these species have been the focus of many studies, it has been unclear whether they are indicative of insect decline at large. A recent study has now shown that the decline of all insects is not as bad as that of bees; it’s worse.

From an ecological standpoint, few animals are more important to environmental stability than insects. They serve as the main pollinators for many environments allowing the propagation of plants, including the fruits and vegetables we eat. In addition, insects serve as a vital part of food webs and are the main food source for a variety of reptiles, birds, and mammals. They are even eaten by humans in many cultures. In fact, insect farming for human consumption may be the future of food due to its low environmental impact and high protein content. Needless to say, the results of this new study published in PLOS One should be quite startling.

The study, conducted by Caspar Hallmann and his team, took place over the span of 27 years in 63 nature preserves in Germany. In this time the researchers were able to take hundreds of samples of insect biomass. This was done using malaise traps, large, tent-like structures typically used to capture flying insects. The traps were then inspected and the biomass, the total mass of the insects, was measured. The authors point out that insect biomass is a better indication of overall insect trends versus the number of individuals, as is used in many species-specific studies.

The results of this extensive study show that there was a staggering 76% loss of insect biomass. Even more disconcerting is that the researchers do not know why this happened. While the typical factors affecting insect populations, such as inclement weather, were present over the course of the study, statistical analyses showed that they were insufficient in explaining the radical insect loss. The authors note that the decline could, in part, be attributed to adverse agricultural practices (i.e. pesticide usage) in fields surrounding the studied areas. Perhaps most unsettling is that these results come from nature preserves, areas that are meant to counteract ecological devastation.

Admittedly this study, while impressive in duration, was fairly limited in geographic range. Even though the malaise traps were spread across a variety of habitat types, the entire study took place exclusively in protected low-altitude German nature areas. The results, therefore, are indicative of insect decline in similar areas of Western Europe, but more studies will have to be performed to determine global insect biomass trends.

This study represents a crucial first step in insect preservation. It brings much-needed attention to how vulnerable all insect populations are, not just those that are highly studied. Future studies will need to be done in order to determine if other insect populations are facing similar declines, what the long-term repercussions will be, and most importantly what in the world is killing all of these insects. With how integral insects are to our environment, this study should be just the bug-inning.