A group of European scientists has analysed 27 years worth of data on flying insects to reveal a startling decline in insect biomass. The researchers from the Netherlands, Germany and the UK, used data on total insect biomass recorded using Malaise traps deployed in over 60 German nature protection areas. They estimated a biomass decline of 76% over the study period. The mid-summer decline was even higher at 82%. Previous studies have shown declines in several groups of invertebrates such as butterflies, wild bees and moths. The decline is apparent regardless of habitat type. Whilst the authors rule out changes in weather, land use or habitat characteristics as possible causes, they are not certain of the causal factors, though they suggest that agricultural intensification may be a factor. Whatever the reason for this decline, the research team describe the decline as 'alarming, ever more so as all traps were placed in protected areas that are meant to preserve ecosystem functions and biodiversity.' Flying insects play an important role in foodwebs, so any dramatic change in their numbers is expected to have implications for other species, such as insect-eating birds.

Further information

• Hallmann, C.A. et al. (2017). More than 75 percent decline over 27 years in total flying insect biomass in protected areas. PLOS ONE. https://doi.org/10.1371/journal.pone.0185809