Coastpath
Building on what GillT57 said there is also a decline in service for local people. Holiday home owners don't need an optician, dentist, vet etc. These businesses become unviable and close and locals, often elderly, are forced to travel further for essential services. This is made more difficult as buses only operate during the summer...less residents mean they are unprofitable and don't run out of season.
Yes! This happens in villages around the town where I live. In summer they are bustling. The locals can't get parked, tables in restaurants are rare as hens' teeth, every shop is packed, so you can't just pop in for a loaf of bread without standing in a 10 minute queue, but at least the economy thrives.
In winter, the local shop is only open for an hour a day, so if you run out of bread you have to drive to a supermarket miles away (if you have a car), pubs close at 9.00pm and the place is like a ghost town. Most houses are empty, and people can be a bit scared of being alone, which causes problems with mental health.
Schools closed years ago, the bus service stopped not long after, so there are few families and older people who can't drive to a doctor, chemist of Post Office move out too - the village ones moved on when it wasn't worth being there. Holidaymakers don't need services like that, and villagers don't need postcards and seaside rock. Young people leave as soon as they can, and can't afford to come back when they have families.
In my city, 30 miles from the villages there are whole streets of student accommodation. Not the purpose-built type, but larger terraced houses that used to be ideal for families. They house 6 students each, but none of them pay council tax, despite getting bins emptied etc. The council is already on a shoestring budget thanks to cuts, so services for everyone drop, and families are driven out.
In both cases, the only winners are the landlords who rent out the holiday homes and student houses. I would tax both types of landlord - and don't get me started about Air B&B!