Temperature drives variation in flying insect biomass across a German malaise trap network

Abstract

Among the many concerns for biodiversity in the Anthropocene, recent reports of flying insect loss are particularly alarming, given their importance as pollinators, pest control agents, and as a food source. Few insect monitoring programmes cover the large spatial scales required to provide more generalizable estimates of insect responses to global change drivers. We ask how climate and surrounding habitat affect flying insect biomass using data from the first year of a new monitoring network at 84 locations across Germany comprising a spatial gradient of land cover types from protected to urban and crop areas. Flying insect biomass increased linearly with temperature across Germany. However, the effect of temperature on flying insect biomass flipped to negative in the hot months of June and July when local temperatures most exceeded long‐term averages. Land cover explained little variation in insect biomass, but biomass was lowest in forests. Grasslands, pastures, and orchards harboured the highest insect biomass. The date of peak biomass was primarily driven by surrounding land cover, with grasslands especially having earlier insect biomass phenologies. Standardised, large‐scale monitoring provides key insights into the underlying processes of insect decline and is pivotal for the development of climate‐adapted strategies to promote insect diversity. In a temperate climate region, we find that the positive effects of temperature on flying insect biomass diminish in a German summer at locations where temperatures most exceeded long‐term averages. Our results highlight the importance of local adaptation in climate change‐driven impacts on insect communities.

Using Malaise Traps and Metabarcoding for Biodiversity Assessment in Vineyards: Effects of Weather and Trapping Effort

“…Temperature and radiation are strongly coupled, in particular during the summer period [ 45 , 46 ]. Both were observed to positively influence insect activity rates in earlier studies [ 1 , 8 , 11 ], with ambient temperature having a direct effect on body temperature and thus flight ability [ 47 ]. However, other studies reported that at above-average temperatures in the summer months, the linear relationship breaks down and activity decreases [ 8 , 14 ], so that a temperature optimum curve could actually have been expected.…”

“…A significant loss of biodiversity and biomass is reported, the reasons for which are attributed to habitat destruction, intensified agriculture, invasive organisms, and climate change [ 4 ]. To be able to record the further course of these trends and the reasons responsible for them, systematic monitoring of terrestrial insects, as it is performed in only a few monitoring programs [ 6 , 7 , 8 , 9 ], is essential. However, in addition to the long-term influences of, e.g., agriculture and climate change, environmental and methodological conditions during sampling could have a direct effect on the insect diversity collected and should thus be considered when evaluating data from ecological surveys [ 10 ].…”

“…Insect activity depends on the season and ambient weather conditions [ 11 , 12 , 13 ]. While warm, dry weather can promote activity, especially in the summer months, it can be reduced in cold and rainy weather [ 8 , 13 , 14 ]. Most flying insects are trapped at hot and sunny conditions after it has rained, although there are differences among taxa [ 12 , 15 ].…”

“…Long-term changing temperature or precipitation patterns due to climate change, however, have a lasting impact on insect populations [ 16 ]. For example, flight activity can decrease at above-average temperatures in summer [ 8 , 14 ].…”

“…In this study, we used Malaise traps and metabarcoding to collect and identify insects in vineyards in southwest Germany. As part of a larger effort to establish an insect monitoring program for viticulture, our first aim was to assess if biomass in southwest German viticulture is affected in a comparable way by environmental conditions as it has already been demonstrated in other ecosystems [ 8 , 11 , 12 , 13 , 14 , 15 ]. We tested the following hypothesis: (H1) (a) cool temperatures, (b) precipitation, and (c) wind reduce the biomass of trapped insects.…”