M-AARE - Coupling atmospheric, hydrological, hydrodynamic and damage models in the Aare river basin, Switzerland

The triggering mechanism and the temporal evolution of large flood events, especially of worst-case scenarios, are not yet fully understood. Consequently, the cumulative losses of extreme floods are unknown. To study the link between weather conditions, discharges and flood losses it is necessary to couple atmospheric, hydrological, hydrodynamic and damage models. The objective of the M-AARE project is to test the potentials and opportunities of a model chain that relates atmospheric conditions to flood losses or risks. The M-AARE model chain is a set of coupled models consisting of four main components: the precipitation module, the hydrology module, the hydrodynamic module, and the damage module. The models are coupled in a cascading framework with harmonized time-steps. First exploratory applications show that the one way coupling of the WRF-PREVAH-BASEMENT models has been achieved and provides promising new insights for a better understanding of key aspects in flood risk analysis.

Virus infections and winter losses of honey bee colonies (Apis mellifera)

Apiculturists have recently been confronted with drastic and inexplicable winter losses of colonies, and virus infections may be involved. Here, we surveyed 337 Swiss honey bee colonies in the winter of 2005 and 2006 and categorized their health status as: 1. dead (= no or few live bees left); 2. weak (= dwindling, high mortality of adult bees); or 3. healthy (= normal overwintering colony). From each colony, pooled adult workers were analyzed for deformed wing virus (DWV), acute bee paralysis virus (ABPV), chronic bee paralysis virus (CBPV) and Kashmir bee virus (KBV). Neither KBV nor CBPV were found, but significantly higher ABPV and DWV infections were found in dead vs. weak vs. healthy colonies (except DWV in 2006 between weak and healthy). Moreover, ABPV and DWV loads were positively correlated with each other. This is the first report demonstrating statistically significant correlations between viruses associated with Varroa destructor and winter mortality.

Winter Losses of Honeybee Colonies (Hymenoptera: Apidae): The Role of Infestations With Aethina tumida (Coleoptera: Nitidulidae) and Varroa destructor (Parasitiformes: Varroidae)

Multiple infections of managed honeybee, Apis mellifera, colonies are inevitable due to the ubiquitous ectoparasitic mite Varroa destructor and might be an underlying cause of winter losses. Here we investigated the role of adult small hive beetles, Aethina tumida, alone and in combination with V. destructor for winter losses and for infections with the microsporidian endoparasite Nosema ceranae. We found no significant influence of A. tumida and V destructor alone or in combination on the numbers of N. ceranae spores. Likewise, A. tumida alone had no significant effects on winter losses, which is most likely due to the observed high winter mortality of the adult beetles. Therefore, our data suggest that A. tumida is unlikely to contribute to losses of overwintering honeybee colonies. However, high losses occurred in all groups highly infested with V. destructor, supporting the central role of the mite for colony losses.

Future storm surge impacts on insurable losses for the North Sea region

The influence of climate change on storm surges including increased mean sea level change and the associated insurable losses are assessed for the North Sea basin. In doing so, the newly developed approach couples a dynamical storm surge model with a loss model. The key element of the approach is the generation of a probabilistic storm surge event set. Together with parametrizations of the inland propagation and the coastal protection failure probability this enables the estimation of annual expected losses. The sensitivity to the parametrizations is rather weak except when the assumption of high level of increased mean sea level change is made. Applying this approach to future scenarios shows a substantial increase of insurable losses with respect to the present day. Superimposing different mean sea level changes shows a nonlinear behavior at the country level, as the future storm surge changes are higher for Germany and Denmark. Thus, the study exhibits the necessity to assess the socio-economic impacts of coastal floods by combining the expected sea level rise with storm surge projections.