Spatio-temporal dynamics and sensitive distance of nighttime light environment in Pearl River Delta Protected Areas, China.

Protected areas (PAs) are important barriers to ensure the ecological security of territory. Light pollution is a threat to PAs, which is particularly obvious in the urban agglomeration environment. We used multi-source big data (satellite remote sensing light data, land cover types and points of interest) to quantitatively analyze the temporal and spatial dynamics of nighttime light in the PAs of the Pearl River Delta (PRD) urban agglomeration from 2000 to 2018, the correlation between the night light environment within the PAs and human activity intensity outside, as well as the sensitive distance of the PAs to artificial light interference. The results showed that the total value of nighttime light data of PAs in the PRD increased from 71107 nanoW·cm·sr to 127682 nanoW·cm·sr from 2000 to 2018, the mean value per pixel increased from 15.3 nanoW·cm·sr to 23.7 nanoW·cm·sr, and the lighted ratio increased from 73.3% to 86.4%, indicating that the nighttime light environment of PAs in the region were facing cumulative deterioration risks and serious challenges. The nighttime light intensity of the PAs in the core area of the PRD was much higher than that in the peripheral areas such as Zhaoqing and Huizhou, whereas the expansion degree of the PAs in the peripheral areas was higher than that in the core area. The nighttime light environment inside the PAs was positively correlated with the intensity of human activities around it. The most sensitive distance of the PAs to the artificial light interference around it was 10 km, and the interference degree tended to be stable after 30 km. We proposed that 0-10 km area outside the boundary of the PAs should be the light control core zone and 10-20 km area as the control buffer zone.