MARRAKECH, Morocco - An ancient city on the rim of the Sahara desert, Marrakech has been a magnet for tourism since the 1960s, when hippies dubbed it "the city of four colors" - for its blue skies; its backdrop of white, snow-capped peaks; the red walls of its medieval fortifications; and the sprawling green palm grove on its outskirts.

But one of these colors is fading fast. Legions of tall, swaying palms are yellowing and sickly, parched by drought that climate-change experts predict may worsen as the planet warms.

Mass tourism, land developers, golf courses, and rich Europeans' closed-off luxury villas are squeezing out farmers from the grove.

For generations, farming families here lived in symbiosis with the palms, harvesting their fruit and using them as shelter while tending to the trees' health. Most now have been pushed out by land prices that have been pushed up by tourism.

The pace of destruction is staggering.

In 1929, Morocco's then-French rulers measured the palm grove at 40,000 acres - an area nearly 50 times that of New York's Central Park. By 1998, it had declined to nearly 30,000 acres. Since then, the grove has shrunk by nearly half, to an estimated 16,000 to 19,000 acres.

Water is a big problem, for both the trees and the people who live under them.

Fatima Lemkhaouen and her two dozen brothers, in-laws and children live crammed in one of the few

douar

, or traditional hamlets, still standing in the grove.

They have no electricity, or sanitation. The guard of one of the luxury villas next to their mud home passes over a hose to fill their plastic jugs and metal basins.

"We love the palm grove, but I don't think it's for us anymore," says Lemkhaouen, 29. Local officials, she adds, have rebuffed their appeals for a public well. "They just want us out," she surmises.

The grove was planted in the 11th century under the Almoravid dynasty, which founded the City of Marrakech. Its empire extended from present-day Senegal to Spain and Portugal.

The United Nations' cultural arm, UNESCO, included the grove when it added Marrakech to its list of World Heritage sites in 1984.

The grove's farmers practiced an age-old technique known as "three-layered crops": wheat and vegetables on the arid soil, fruit trees at a man's height, and dates from the palm trees.

Hundreds of miles of

khettarras

- man-made canals and cisterns - brought water from the hills for plants to survive in the desert climate.

This ecosystem is collapsing.

Drought and heavy pumping for extensive agriculture in the hills around the grove have drastically depleted water reserves. The water table - a decade ago 30 feet underground - is now at 65 yards.

Simultaneously, Marrakech became a top tourism destination. Even small plots in the palm grove now fetch as much as $1.5 million, creating pressure to sell to promoters. The Lemkhaouens' landlord is not renewing the family's lease.

As a UNESCO heritage site, the grove is supposed to be protected by the Moroccan government. Marrakech City Hall, the national government and private partners have committed the equivalent of $13 million to replant 400,000 palm trees by 2012.

The plan, launched by Morocco's King Mohammed VI and headed by one of his sisters, has already brought the number of palm trees from 100,000 in 2006 to more than 260,000, said forestry engineer Abdellilah Meddich. But most of the new trees are being planted in touristic zones near Marrakech instead of throughout the palm grove, he says.

Marrakech Mayor Omar Jazouli acknowledges that most of the palm trees are "in an appalling state." But he views tourism as the savior, not the bane, of the grove.

"From the air, you can see that all the trees in private ownership - golfs, hotels and villas - are being superbly looked after," he says. Every construction site for a new villa is required to survey its palm trees and can move them - not cut them down - only if building is impossible otherwise, he says.

Jazouli concedes the building boom is driving out farmers, but says the benefits outweigh that loss for Marrakech's 850,000 people. Tourism and construction have driven salaries way above the national average, he said. With just 7 percent unemployment, Marrakech is nearly three times below the rest of the country.

Others see a less-rosy future.

"Parts of this beautiful palm grove are becoming a construction dump," said Sylvie de Gouy, the owner of the villa who shares her water with the Lemkhaouen family. Gouy, a dentist in Lille, France, comes to her Marrakech villa once a month.

"You can't buy a house down here if you don't appreciate the Moroccans and living alongside them," she said, sipping a glass of mint tea at Lemkhaouens' modest breeze-block house across the wall from her mansion.

But even for Gouy, water is now an issue. The private well to keep her garden green ran out last summer.