Figure 1.

Flowchart on how artificial light may affect species at the population level. The most direct way is immediate impact on the survival of the individual (left arrow). However, light may have effects on the physiology, behaviour and life-history traits of the individual. For example, if light leads to untimely reproduction causing high juvenile mortality, fitness is affected and hence population size may decrease. Effects of light on the environment of a species may cause even more indirect effects on fitness of a species. These effects include general habitat changes, and cascading effects, for example by the availability of prey species which may themselves be affected by all possible routes shown. (Online version in colour.)