[Jevons Paradox: Technological progress that increases efficiency tends to increase consumption.]HSR is promoted as something that can sort out nasty carbon producing aircraft on domestic routes. It has done this on Paris-Lyon and Madrid-Seville, but this ability to trash a single air route should not be interpreted as something than can dent the growth of air travel itself. Germany has one of the largest HSR systems in the world and has seen an explosion in internal air travel.
HSR does not reduce the fuel consumption of domestic aviation or reduce annual carbon emission from aircraft. It allows airlines and airports to recycle much needed take off and landing slots and exploit other market opportunities aimed at making us all fly more often than we do already.
They have plenty of high-speed mainlines but they only have two true HSL lines that are not that long. They need more 320 km/h lines in order to reduce air travel internally.