Rapid development in the coastal region of Comporta has alarmed locals and environmentalists, who fear a repeat of the unchecked growth seen in Portugal's southernmost Algarve province, long a package holiday destination.

Dubbed "the new Portuguese Riviera", Comporta has drawn high-profile visitors including Oscar-winning actor Nicole Kidman and Princess Caroline of Monaco.

Real estate consultancy Knight Frank lists the region, located about an hour's drive south of Lisbon, among the five most sought-after luxury residential markets worldwide.

"Comporta appeals to a wealthy clientele seeking nature, privacy and wellness," the company wrote in a recent report.

French designer Christian Louboutin was among the first international figures to discover Comporta's charm, opening a hotel in Melides, a small village of whitewashed houses with blue doors.

Princess Eugenie, whose uncle is Britain's head of state King Charles III, splits her time between London and Comporta, drawn by the region's relaxed lifestyle.

"I can go to the supermarket in sportswear, my hair in disarray, and nobody cares," she told the podcast Table and Manners in 2023.

- 'Overrun by tourism' -

Environmentalists warn that development projects threaten the region's unique mix of dunes, pine forests, gnarled cork trees and an endless patchwork of rice fields.

Campaign group Dunas Livres (Free Dunes) says eight "mega-projects" are under development, each covering hundreds of hectares, which will increase water consumption in a region already threatened by drought.

"These hotel complexes, with golf courses, swimming pools and a very large number of tourist beds, obviously consume a lot of water," Catarina Rosa, a biologist with the group, told AFP.

"Comporta, a true natural treasure, is being overrun by tourism," she added.

The transformation traces back to the collapse of the Espirito Santo bank during the 2011 debt crisis.

The Espirito Santo family were once the sole owners of the 12,000-hectare Herdade da Comporta estate but sold large parcels to developers following the collapse of their banking empire.

Since then, investors including French developer Claude Berda's Vanguard Properties and US-based Discovery Land Company have launched private residences, hotel complexes and golf courses.

Discovery Land is behind the CostaTerra Golf and Ocean Club, planned to feature nearly 300 luxury villas.

- 'Frenzy' -

Local residents have mixed feelings about the changes.

Some have sold small properties for staggering sums, while others worry that skyrocketing real estate prices are disrupting their way of life or forcing them out.

A small house worth 20,000 euros ($23,000) two decades ago is now valued at one million euros, said Jacinto Ventura, a farmer and president of a local association in Melides.

"This real estate bubble, with no clear end in sight, has driven prices into a frenzy. And this frenzy has forced a large portion of the population to move away," he told AFP.

Residents also complain about restricted access to public beaches and rising costs in local shops since the arrival of wealthy visitors.

While some are leaving the area, others are trying to hold on.

Belinda Sobral, 42, a former engineer who reopened her grandparents' tavern in the nearby town of Grandola, said the problem is not tourism itself, but the pace of development.

"It has been too fast, without planning or respect for the locals," the mother of two said.

"I want to preserve the identity of this place. Without memory, Comporta will become another Ibiza -- a resort like so many others," she added.