Page - 85 - in Critical Issues in Science, Technology and Society Studies - Conference Proceedings of the 17th STS Conference Graz 2018

species. These relationships could lead to cascading effects in ecosystems when strong dependencies on the species are concerned (Fang 2010). Additionally, indirect effects have to be taken into consideration, for example when a species is suppressed or even driven to extinction by a gene drive and its ecological niche is filled by another species (David et al. 2013). For example eradication of the mosquito species Aedes aegypti to eliminate dengue would result in an open niche for Aedes albopictus which may transmit dengue as well. Moreover, non-intended effects such as a transfer of the gene drive to non-target species (due to interspecific mating or other potential routes of DNA transfer) must also be taken into account. In the end, besides an adverse influence on ecosystem functions, ecosystem services (i.e. services for mankind) may also be affected by changes in the concerned ecosystems. The biting midges of the family Ceratopogonidae which bite humans and thereby transmit diseases are a good example, because they are also pollinators for tropical crops such as cacao. Eradication may in an extreme scenario “result in a world without chocolate” (Fang 2010, 433). Moreover, gene drives potentially lead to a loss in diversity. Since a gene drive essentially equips a whole population with the same set of genes or eradicates the population as a whole, it can be viewed as a reduction in diversity. Apart from ecological interactions of the gene drive affected species, evolutionary effects should be considered with regard to the potential impact of gene drives on ecosystems. A released gene drive is also exposed to evolutionary processes. These in turn may affect the function and the gene flow of the drive. Gene flow between populations of the target species could influence the fitness of these populations. The establishment of a gene drive in a population can cause the formation of subpopulations and on a greater time scale favor speciation or extinctions. Interspecific gene flow between the target species and related species can occur if mating between viable offspring is possible (National Academies of Sciences 2016). Thereby the fitness of these ‘non-target’ species may be altered. Besides these effects of gene flow, mutations of the drive may lead to unforeseeable effects within directly or indirectly affected species and subsequently in the respective ecosystem. But mutations can cause a resistance against the gene drive as well. It was already shown for CRISPR/Cas-based gene drives that unsuccessful conversion usually leads to the formation of resistance alleles (Unckless, Clark, and Messer 2016; Callaway 2017). Resistance alleles potentially increase in frequency and would thereby limit the further spread of drives within or between populations. Technology assessment The modification of controlling structures like a genome represents a high depth of intervention which tends to trigger long chains of effects in time and space. Moreover, an increasing depth of intervention provides more degrees of freedom for the design or manipulation of functionalities and may thus result in a higher level of technological power and range of exposure. Accordingly, uncertainty and ignorance may increase as well. Technology characterization should therefore consider at least the following criteria (von Gleich, Pade, and Wigger 2013; von Gleich 2013, 60ff): 85