BELBEES Project: Multidisciplinary assessment of BELgian wild BEE decline to adapt mitigation management policy: Final report

The BELBEES project allowed to carefully assess the past and present situation of the wild bee populations in Belgium. The Red List of Belgian wild bees prepared by the BELBEES project shows that on the 399 wild bees recorded in the country: 45 species (12%) are now extinct, 139 species (35%) are threatened or declining, 162 species (41%) are stable or expanding while 53 species (13,3%) are not assessable due to deficient data. Compared to the 1993 assessment, the situation clearly got worse: while already 12% of species appeared declining in 1993, there are now nearly half of the species (48%) that are declining or even extinct. For bumblebees, our analysis revealed that thistles constitute a very important food resource. Their most threatened species are highly dependent on these plants. Floral resource availability decreased significantly, thus threatening most of the specialist bee species and forcing the generalist ones to shift their foraging to other plant species. This resource shift stresses their nutritional fitness. The main agriculture crops in Belgium do not require insect pollination. However, some large areas in Vlaams Brabant and Limburg are devoted to fruit production that could highly suffer from pollinator loss. Climate change appeared as a main threat against bumblebees because most of them are very sensitive to heat stress (occurring during heat waves). Models show that most species may disappear in the next decades. While urbanization has been clearly involved in change in bumblebee fauna, land use and climate change appear as linked factors. No population structuring was found at country scale (Belgium) and only low levels of structuring in an international sampling for seven bumblebee species at continental scale (Europe). This indicates that there is no limitation in gene flow, not even for the restricted bumblebee species. A careful assessment on microbial pathogens in selected wild bee species showed that they include numerous previously unknown taxa, with few or no connection with ...