Geobotanical relevés of seashore vegetation on sandy terrain near the Varzuga river mouth (Tersky Coast, Murmansk Region) from 1991 and 2013 are compared, and an essential rise in abundance and frequency of Red Data Book species Thymus subarcticus Klok. et Shost. is discussed. The table of relevés from 1991 and 2013 is provided. Thymus subarcticus is quite common in dry grasslands and disturbed habitats on Tersky Coast, where it forms large cushions. It took a little more than two decades for this species to advance into open plant communities of ass. Elymo-Festucetum arenariae (Nordh. 1955) Tx. 1966 on seashore terrace and take dominance there. The succession is directed towards dry grasslands of ass. Cetrario nivalis-Festucetum ovinae (Nordh. 1943) Dierssen 1992. This association had been described earlier from the White Sea shore. Plant communities of the seashore beach and dune complex are regarded as endangered habitats in the list of habitat types to be protected under the Berne Convention (1996), and the area investigated is very suitable for monitoring these habitats, the course of the succession, and Red Data Book species. The regime of waterside-protective territories along rivers and seashore is quite appropriate for protection of these habitats, provided that it is combined with prohibition of off-road vehicle traffic and uncontrolled plant picking.