Changes in light pollution in the Pan-Third Pole's protected areas from 1992 to 2021

Abstract

Light pollution driven by human activities is undergoing unprecedented changes, which may profoundly impact biodiversity and habitat conservation. The Pan-Third Pole (PTP), one of the world's richest biodiversity regions, is experiencing rapid population growth and urbanization, along with continuously increasing light pollution. Protected areas (PAs) represent a cornerstone in safeguarding biodiversity and habitats. However, light pollution in the PTP's PAs also shows a growing trend. Using the harmonized global nighttime light (NTL) data, we studied the spatio-temporal variation in light pollution in the PTP's PAs from 1992 to 2021. The results showed that the light pollution area in the PTP's PAs increased by about 3-fold from 1992 to 2013 and about 1.2-fold from 2014 to 2021. The levels of increase varied across regions and altitudes. Southeast Asia and Centre Asia had the highest and lowest rates of increase, respectively. Higher-altitude areas had higher rates of increase, especially in areas above 3000 m. The increases in light pollution have a close relationship with urban expansion. In the PAs and their surrounding area, an increase of 1 km2 in the urban area resulted in at least 9 km2 of the PAs being affected by light pollution.