Satellite evidence for small biophysical effects of transport infrastructure in the Qinghai-Tibet Plateau

Transport expansion is detrimental to natural ecosystems and yet to what extent it can impact nearby alpine ecosystems is not well understood. This case study in Qinghai-Tibet railway and highway explores the bio-physical effects of transport infrastructure in terms of remote sensing-based greenness, wetness, dryness, and heat according to a space-for-time substitution method. We estimate highly diverse changes across road sections in all the indices from both multiyear-mean and long-term perspectives, and no clear biophysical gradients with distance away from the transport lines, except for a gradual decrease in multiyear-mean heat and wetness. In a 500-m buffer zone, those indices on average are 0.1-15.7% lower or higher than the references and the dis-parities increase or decrease significantly from 2000 to 2021 alongside 15-48% of the transport lines. We further find that the estimated biophysical changes depend strongly on the reference conditions and the elevation gradients nearby the roads. Also, the road sections surrounded by some urban/crop lands show much more frequent "significant" trends than the others, confirming strong land use effects on the biophysical dynamics in alpine regions. Nevertheless, it remains open to debate to what extent transportation contribute the land use activities near the roads. We argue that highways and railways unlikely strongly impact the biophysical con-ditions in alpine regions due to small road width, widespread nature reserves, various protective measures, and low accessibility to surroundings if they are fenced. Our results highlight the small biophysical impacts of transport infrastructure on roadside natural ecosystems in the Qinghai-Tibet Plateau and suggest prioritized attention to the direct damages to soil and vegetation by transport construction and the habitat disruption, biodiversity change, and road kills by transport operation for developing an environment-friendly transport system.