Abstract: Urban festive lighting, represented by light shows, can boost nighttime economy, but the threat of high-intensity light interference to ecological spaces cannot be overlooked. With the Guangzhou International Light Festival as a case, we constructed a high-resolution ground-based observation network covering up to 16 km from the light source center, to accurately quantify the light disturbance within ecological spaces and its impact distance. The results showed that, compared with normal nights without light shows, during the light festival period, the average night sky brightness within 16 km of the Canton Tower (light show center) increased by more than 0.26 mag·arcsec^-2(increase >1.6%), with a maximum increase at a single point for a single observation reaching 0.65 mag·arcsec^-2(increase 4.2%). The dynamic high-frequency fluctuations of light exhibited significant nonlinear characteristics. At a distance of 6 km from the light source, both the standard deviation of zenith brightness (0.19) and the instantaneous fluctuation amplitude (3.5%) exceeded those at the source center, forming a dynamic peak zone where far-field intensity was stronger than near-field intensity. This study found the significant impact distance of light shows was 6-7 km. Based on the finding, we proposed planning and management strategies such as delineating a 6 km light-ecological buffer zone and avoiding peak bird migration periods, providing a scientific basis for coordinating the development of the nighttime economy and the protection of nocturnal ecosystems.

Key words: light festival, light disturbance, ecological space, significant impact distance