The Upper Rhine valley is not only a metropolitan area but also one out of 30 “Hotspots of Biodiversity” in Germany. In spring and summer time the river regularly breaks its’ banks and create temporary wetlands having a high floral and faunal biodiversity all along the river Rhine. These valuable landscapes are also protected by designated natural and European protection areas (bird sanctuaries, nature reserves, Natura 2000 sites) that likewise cover a large proportion of the entire Upper Rhine valley. Besides microcrustaceans, insects are the most abundant taxa in seasonal wetlands. Aquatic insects are not only an important food resource for inhabitants of the water body like dragonfly nymphs or amphibians. As imagines they serve as food for terrestrial predators such as birds, bats, spiders and adult dragonflies. The high biomass of mosquitoes (Culicidae) and other midges is not only a food resource for animals but also a nuisance to humans. Therefore mosquito control is widely established in wetlands all over the world. At the moment the most common agent used is Bacillus thuringiensis var. israelensis (Bti), a bacterium producing toxic proteins very specific to the larvae of Nematocera.

To enhance human comfort the Bti-based mosquito control was originally established in the year 1976 and initiated in an area between Speyer and Karlsruhe. This area enlarged over time up to 350 km along the River Rhine. Each treatment with Bti leads to a reduction of the target organism mosquito of more than 90 %. Depending on the river flood Bti is applied up to 12 times a year. In Germany, Bacillus thuringiensis subsp. israelensis Serotype H14, Strain AM65-52 is registered as "existing active substance" reviewed under the biocide-regulation (528/2012) effective since September 2013.

The application of the larvicide Bti is known as environmentally friendly alternative to other insecticides. However, there are indications that also non-target organisms could be affected by the Bti treatments. The toxic mode of action in the target organism Culicidae is very similar to the mode of action in larvae of Chironomidae which are not the target of Bti-treatments in Germany. These non-biting midges are the most important and abundant food resource in the wetlands for terrestrial and aquatic predators which is why their lack may lead to indirect effects causing changes in the food web. Although direct effects of Bti towards non-target organisms are studied in laboratory and semi-field studies there is a lack of long-term data of indirect effects on non-target species. The current state of knowledge regarding indirect effects is based on just a few long-term studies that show a varied picture depending on the study area. Recently, indirect effects could be recorded for breeding birds in a study conducted in the Camargue region in France. In the year 2013 several master thesis were conducted at the University of Koblenz-Landau referring to this topic. The obtained study results already show some initial indications for potential effects and are summarised in a final report (Report PDF).