Limiting the duration of lighting

Where the removal of lighting is not possible, ecological management considerations must then shift to how the form of night-time light pollution can be altered to reduce its potential impacts. The simplest option here is to change the period for which lighting occurs; so-called part-night lighting. Central management systems can allow the timing and intensity of grid-based lighting to be controlled, already resulting in some broad-scale decreases in lighting during periods when it is not needed.

The ecological consequences of part-night lighting are not well understood and constitute an important future research topic, but as a general principle, reducing the duration of lighting seems likely to have positive or neutral ecological benefits. Given current knowledge, lighting could be switched off or dimmed during particularly critical times when biological activity is especially high or significant, such as when foraging, breeding or dispersal/migratory activities are occurring. Therefore two obvious strategies are to switch off lighting during particular seasonal or nightly periods. However, the timing of those switch offs is difficult. Unfortunately it seems likely that the times when lighting is most important to humans, the hours immediately after dusk and immediately before dawn, are also those at which it has the most significant impact on many other organisms.

In some limited circumstances, changing the duration of night-time lights on substantially shorter time-scales might usefully reduce their impacts. For example, it has been shown that avian collisions with communication towers tend to be much lower when using flashing than non-flashing (steady-burning) lights.