The First Dark-Sky Map of Thailand: International Comparisons and Factors Affecting the Rate of Change

Farung Surina (), Thanayut Changruenngam (), Jinda Waikeaw, Suruswadee Nanglae, Saran Poshyachinda, Boonrucksar Soonthornthum and Michael F. Bode
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Farung Surina: Faculty of Science and Technology, Chiang Rai Rajabhat University, Chiang Rai 57100, Thailand
Thanayut Changruenngam: Faculty of Science and Technology, Chiang Rai Rajabhat University, Chiang Rai 57100, Thailand
Jinda Waikeaw: Faculty of Science and Technology, Chiang Rai Rajabhat University, Chiang Rai 57100, Thailand
Suruswadee Nanglae: Faculty of Science and Technology, Chiang Rai Rajabhat University, Chiang Rai 57100, Thailand
Saran Poshyachinda: National Astronomical Research Institute of Thailand, Chiangmai 50180, Thailand
Boonrucksar Soonthornthum: National Astronomical Research Institute of Thailand, Chiangmai 50180, Thailand
Michael F. Bode: National Astronomical Research Institute of Thailand, Chiangmai 50180, Thailand

Sustainability, 2025, vol. 17, issue 21, 1-20

Abstract: We present the first dark-sky map of Thailand, derived from calibrated Visible Infrared Imaging Radiometer Suite (VIIRS) satellite data spanning 2012–2023. Artificial night-sky brightness was classified into 14 levels, with Classes 1–9 defined as potential dark-sky areas where the Milky Way remains visible. International comparisons with the United Kingdom, Chile, and Botswana reveal that Thailand has undergone the steepest decline, losing 15.4% of pristine skies since 2012, while the UK remained stable (+0.8%), Botswana nearly unchanged (−0.7%), and Chile moderately degraded (−5.3%). A correlation analysis shows strong negative associations between potential dark-sky area and both GDP ( r = − 0.65 ) and population ( r = − 0.68 ), while inflation ( r = 0.26 ) and unemployment ( r = 0.24 ) exhibit weak influence. Five algorithms, including GLM and machine learning models, were tested; among them, the Decision Tree achieved the lowest relative error ( 0.4 % ± 0.3 % ), with ensemble methods and GLM performing comparably and Deep Learning being less accurate. By 2023, over 60% of Thais lived under skies too bright to observe the Milky Way by naked eye, and one-fifth were exposed to intensities preventing dark adaptation. Thailand’s rapid transition to LED street lighting after 2015, while energy-efficient, has intensified skyglow. Protecting remaining dark-sky areas requires urgent policies, linking conservation to human health, biodiversity, cultural heritage, and sustainable development.

Keywords: dark-sky conservation; environmental astronomy; lighting policy; light pollution; night-sky brightness; satellite remote sensing; sustainable development; Thailand; tourism and culture; visible infrared imaging radiometer suite (search for similar items in EconPapers)
JEL-codes: O13 Q Q0 Q2 Q3 Q5 Q56 (search for similar items in EconPapers)
Date: 2025
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