Table 2.

Overview of relevant questions for the ERA of GE gene drive organisms in terms of spatial and temporal complexity

Question	Relevance	Which methodology is available?
1) Can genetic stability be controlled in following generations?	Self‐replication and environmental as well as epigenetic effects can lead to emergence of next generation effects not observed in the first generation.	Several generations should be observed under controlled conditions applying a wide range of defined environmental conditions, which allows the assessment of at least short‐term evolutionary effects. The outcome has to be put in context to questions 2 and 3.
2) How can genetic diversity in the target population be taken into account?	In most cases, a high degree of genetic diversity exists in natural populations. These heterogeneous, genetic backgrounds can trigger unexpected effects not observed in lab populations.	In most cases, the inserted genes cannot be tested in interaction with the genetic diversity within natural populations. For example, in insects, the strains reared in the lab might represent only a small selection of the genetic diversity within wild populations.
3) Will there be any gene flow to other species?	If gene flow is possible and hybrid offspring are viable, the resulting organisms have to be seen as new events that need to be assessed separately from the original GE organisms.	It might be possible to perform hybridization experiments under controlled conditions. Results have to be put in context with questions 1 and 2.
4) How can population dynamics and life cycle aspects of the target species be integrated?	Bottlenecks in the population dynamics, e.g., due to the winter season, might result in inbreeding and changes in genetic variability. Bottlenecks can have a significant impact on tipping points within the population dynamics.	Large‐scale population effects can be modeled, but empirical investigations are difficult. Further, any results have to be interpreted in the light of questions 1 and 2.
5) Can the receiving environment be defined in regard to relevant interactions and confined in regard to potential spread?	Adverse effects can emerge from interaction with different components of the environment (such as associated microbiomes, symbionts, food webs, predators). Terrestrial and aquatic systems have to be taken into account, as well as complex interrelations (such as signaling pathways) and behavioral aspects. Interrelations may vary greatly throughout the life cycle (different developmental stages such as egg, larva, pupa, adult).	These aspects have to be assessed case by case and step by step. In most cases, long‐term, cumulative, and combinatorial effects cannot be tested or investigated ex ante.

ERA = environmental risk assessment; GE = genetically engineered.