Pungent brown sewage spews into the Pacific ocean. In the background, cranes put up hotels and beachfront apartments.

Once home to monkeys, turtles and other rare wildlife, this stretch of coast in northwest Costa Rica is developing so fast that it is tarnishing the country's reputation as a destination for eco-tourists.

Some 1.4 million people visit Central America's richest country every year, but they no longer come just for the national parks that cover more than a quarter of its area and are home to almost 5 percent of the world's plant and animal species.

They also want sand, surf and even real estate.

The biggest stimulus came when the airport at nearby Liberia began handling international flights five years ago, putting the previously little-known Guanacaste province within, for example, three hours of Miami.

With tropical sunshine, sandy beaches and surf, developers saw a chance to attract everyone from surfers and honeymooners to US retirees seeking a second home, transforming sleepy towns with names like Tamarindo, Quepos, Playas del Coco and Jaco.

The result is rampant construction that environmentalists fear could balloon into noisy, sprawling resorts with cruise ship ports and golf courses like those of Cancun, Mexico, which guzzle water and pollute the environment.

"These cases of poorly planned tourist developments in Costa Rica could affect the well-deserved reputation as a pioneer in eco-tourism," said Ronald Sanabria, a Costa Rican who works for the Rainforest Alliance, an international advocate for sustainability.

Already, Costa Rica has lost up to half of its monkey population in the last 12 years as developers expand into their jungle habitat, according to scientists at the University of Costa Rica.