(CNN) -- For centuries lighthouses have shone a friendly beam for sailors, fishermen and ferry passengers alike, steadily providing safe passage ashore and capturing a special place in the public imagination.
However, with the advent of sophisticated and increasingly cheap Global Positioning Systems (GPS), a question mark now looms over the future of these iconic coastal beacons.
"These are worrying times for lighthouses," said Jeremy D'Entremont, president of the American Lighthouse Foundation. "Everyone loves them, but as far as the government is concerned, they're not exactly a spending priority."
According to D'Entremont, although about 75% of lighthouses are still operating as "navigational aids" in the United States, federal funding is now almost exclusively limited to the mechanical maintenance of the lights.
"This leaves little or nothing for upkeep of the buildings themselves," he said. Without the support of local groups or the backing of a private buyer, he added, many lighthouses are "just left to rot."
The ardent pharologist, who until recently was responsible for compiling an ongoing database of lighthouses worldwide, estimates there are a total of 10,000 to 12,000 in existence.
But nearly all of them face the same problem. "Since the global financial crisis, it's obvious that there's less and less money for the preservation of historic buildings," he said.
Peter Williams is the treasurer of the World Lighthouse Society. "Long gone are the days of the diligent lighthouse keeper, tending personally to the light and keeping the tower in order," he said.
In Britain, an island whose coastline is peppered with hundreds of lighthouses, the last keeper retired in 1998. Now, according to Williams, all British lighthouses are fully automated and monitored from a few central offices. "They even have self-changing bulbs," he said.
But both Williams and D'Entremont concede that it is difficult to justify ongoing investment in lighthouses, now that their once vital function at sea is being rapidly replaced by new technology.
That may be the case, but lighthouses still "have enormous cultural and historical value," argues Gary Sredzienski, a musician from New Hampshire who aims to swim four miles in freezing water this month to raise money for his two local lighthouses.
"They are incredible feats of engineering, as well as objects of enduring beauty that connect us to our past -- especially for someone like me who comes from a fishing community," he added.
However, the future isn't all bleak. Many lighthouses have become financially self sufficient by transforming themselves into a everything from quirky hotels to final resting places.
"There are some really great lighthouses that have been turned into internationally acclaimed museums, such as the Kinnaird Head in Scotland," Williams said.
Many hundreds more have been converted into unconventional bed and breakfasts. "I would personally recommend a trip to the West Usk Lighthouse B&B in Wales -- they have a hot tub on the roof," he said.
Across the pond in California, D'Entremont points out that the 19th century Farallon Island Light has been transformed into a wildlife observatory, while in Malta, the once decaying Gordon Lighthouse has been revamped into an atmospheric research station.
A few proprietors have gone even further leftfield. The Tillamook Rock Lighthouse in Oregon has been converted into an offshore columbarium, where cremated ashes can be stored.
But is tourism a positive direction for these historic structures to head in? "I'm all for the repurposing of lighthouses," said Williams. "Just as long as the buildings are well preserved."
D'Entremont agrees, but remains concerned about the future of the many "submerged" lighthouses -- those perched on a rock or reef out in the middle of the sea -- that have no easy means of being converted into attractions.
"At my local lighthouse in Portsmouth Harbor (New Hampshire), we regularly fund raise by giving 'haunted tours' and having ghost hunts around the building, for instance. But with offshore lights, you can't do that," he said.
Ironically, it's those lighthouses built out at sea that often reflect the greater historical merit -- due to the extraordinary engineering skills required to build them.
"Look at somewhere like Minot's Ledge Light in Boston," said D'Entremont. "It was built in the mid-19th century a mile out to sea with only a few hours of construction time a day during low tide."
The lighthouse is still standing today despite being pelted constantly with 100-foot waves. It's unlikely, however, to be converted into a gift shop any time soon.