# Evaluation of Light Pollution in Global Protected Areas from 1992 to 2018  
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1 College of Land Science and Technology, China Agricultural University, Beijing 100083, China; [EMAIL_ADDRESS]  
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2 Key Laboratory of Remote Sensing for Agri-Hazards, Ministry of Agriculture and Rural Affairs, Beijing 100083, China  
22 Key Laboratory of Digital Earth Science, Institute of Remote Sensing and Digital Earth, Chinese Academy of Sciences, Beijing 100094, China; [EMAIL_ADDRESS]  
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3 Key Laboratory of Digital Earth Science, Institute of Remote Sensing and Digital Earth, Chinese Academy of Sciences, Beijing 100094, China; [EMAIL_ADDRESS]  
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4 Beijing Municipal Institute of City Planning and Design, Beijing 100045, China; [EMAIL_ADDRESS]  
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Footnote 1: [[https://www.mdpi.com/journal/renotesensing](https://www.mdpi.com/journal/renotesensing)]([https://www.mdpi.com/journal/renotesensing](https://www.mdpi.com/journal/renotesensing))  
Footnote 2: [[https://www.mdpi.com/j](https://www.mdpi.com/j)]([https://www.mdpi.com/j](https://www.mdpi.com/j))  
ecological environment and the diversity of species [10; 11]. However, limited attention has been paid to the global light pollution of PA, given that we are entering a rapid global urbanization era [12; 13]. In general, light pollution has been increasing in most terrestrial ecosystems over the past decades, resulting in considerable impacts on species' habitats and biodiversity conservation [14]. Artificial light has been shown to have ecological effects with different brightness, changing the natural light cycle and affecting its biodiversity [15; 16]. For example, light pollution affects the population of insects [17; 18], the supply of ecosystem services [19], and reduces the physiological effect and reproductive yield of plants [20; 21]. As such, studies on light pollution for biodiversity conservation are urgent [5; 22]. Meanwhile, due to rapid global urbanization, the artificial light in/around PAs has increased significantly and threatened the biodiversity in nearby PAs [23]. Although the global expansion of human activity (e.g., urban sprawl) has posed a noticeable impact on wildlife in PAs, this impact can be quantified by combining remote-sensing observations and ecological models to support sustainable ecological development conservation strategies [2; 24]. The NTL time series data are widely used to characterize the intensity and change of socioeconomic activities [25; 26]. Hence, the NTL data provide an avenue to evaluate the impact of anthropogenic activities in global PAs [27; 28]. From the perspective of biodiversity conservation, NTL can quantify the impact of artificial light on biodiversity loss [29], therefore enabling a host of applications such as habitat fragmentation and loss [30], resource extraction, and human-natural conflicts [31]. As a result, studies on biodiversity conservation using NTL time series data have become a rapidly growing field over the past decades [32]. Previously published studies on NTL impacts on PAs are limited in temporal trend analysis and spatial pattern identification. Given that artificial light can cause habitat degradation, many relevant studies on light pollution have been conducted [33; 34; 35; 36]. To the best of our knowledge, most existing studies focused on statistical analyses of NTL in PAs and the temporal span is limited to 2013 or earlier [23; 35; 36; 37], or local surveys in particular areas [38; 39] as well as in the ocean [40]. It is essential to understand the spatial relationship between the NTL and PAs for better conservation of global ecological environments [41], by mapping the lit areas in/around PAs and characterizing their temporal trends. As such, long-term and temporally consistent NTL time series data are highly required to support these studies to better understand the temporal trends of light pollution in/around worldwide PAs.