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PLOS Science Wednesday: Hi reddit, we’re Caspar and Eelke, and our research shows a more than 75% decline in the biomass of flying insects over 27 years, indicating severe disturbances in many ecosystems – Ask us Anything!
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Hi Reddit, My name is Caspar Hallmann and I am PhD candidate at the Radboud University in Nijmegen, the Netherlands. My research focuses on population dynamics of birds and plants in relation to landscape and climate changes. My name is Eelke Jongejans and I am Assistant Professor at the Radboud University in Nijmegen, the Netherlands. My research focuses on spatial population dynamics: I’m interested in the demographic and driving processes that can explain why certain populations increase in number, while others dwindle. We recently published a study titled More than 75 percent decline over 27 years in total flying insect biomass in protected areas in PLOS ONE. The aims were to see whether the total weight of insects flying in German nature areas has changed over time, and whether a change can be understood by considering climate change, land use change and local changes in plant species composition. The insect biomass data were painstakingly collected by our German co-authors of the Entomological Society Krefeld, using highly standardized traps from 1989 till 2016. Approximately every 11 days they placed a new bottle with ethanol, resulting in 1503 samples collected in 63 different sites. About half of the sites were visited in more than 1 year, resulting in 96 site-year combinations. To analyze this complex dataset we modeled daily biomass as a function of explanatory variable like habitat cluster, weather variables, plant species richness, proportion of land covered by agricultural fields in a 200m radius. While these variables explained a considerable amount of variation between the collected samples, they could not explain the overall 76% decline in insect biomass that we found over the 27 years. We will be answering your questions at 1pm ET – Ask Us Anything! Unsure what to ask? Read an interview with Caspar Hallmann on PLOS Research News.