Nature and extent of ecological impacts of vehicle headlights

Artificial nighttime lighting is a profound anthropogenic pressure on the natural environment. This growing area of international research has focused almost exclusively on emissions from static light sources, such as those from urban streetlights. Meanwhile, virtually nothing is known about the ecological impacts of mobile sources of lighting, most significantly those arising from vehicle headlights. This is despite convincing reasons suggesting the ecological pressure they cause is very different, far more pervasive, and significant. Specifically, compared to streetlights, headlight emissions are: (i) emitted along virtually all of the 36 million km of roads worldwide, significantly expanding their area of influence; (ii) emitted as horizontally projected beams that travel further at higher intensities; and (iii) experienced by organisms as irregularly timed pulses that may cause major perturbations in visual systems and behaviour. We will push the frontiers by determining the nature and extent of impacts on insect vision systems - and consequently their orientation and flight behaviour - caused by light emissions from vehicle headlights. First, we will use modelling and field measurements to characterise the spread of headlight emissions. Second, laboratory experiments will determine associated impacts on animal visual adaptation, orientation and flight behaviour. Finally, these findings will be used to establish current and future spatio-temporal variation in ecological impacts of vehicle headlights. This research has important implications for policy and regulation, because vehicle headlights are increasing in intensity and spectra that may be more ecologically harmful, and there is projected doubling of global traffic levels and 60% growth in global road length by 2050.