A well-known fact: insects play a critical role in food networks and ecosystems. Another known fact: it is mainly terrestrial insects which are pushed further towards extinction through the destruction of their natural habitats. Whether these are limited phenomena, or whether insect die-off is observed globally, however, has thus far remained shrouded in mystery.
This question has now been tackled by an international team of scientists headed by Roel van Klink of the German Centre for Integrative Biodiversity Research (iDiv) with the most comprehensive meta-analysis on this topic to date. To this end, the team analyzed data from 166 longitudinal studies at 1676 locations worldwide; they distinguished between terrestrial and freshwater insects, and they also captured the values separately by countries and regions. The core results: the abundance of insects is decreasing globally by one percent annually.
Doesn’t sound like much? Think again: this number translates to 24 percent fewer insect species after 30 years and a reduction by half over a period of 75 years. The greatest losses were observed in parts of North America and in Europe, among them Germany. Meanwhile, the number of freshwater insects has increased by a solid percent per year.