Exploring for Plants Expedition to study and conserve the palms of Micronesia, September - October 2008

Palau’s Rock Islands are among the most pristine habitats in the Pacific. Unlike most tropical islands, they still support native forests and are not ravaged by exotic invasive plants. They include the only known populations of Ponapea palauensis, the palms we came to study. There are more than 800 Rock Islands, stretching south from the larger volcanic islands of Babeldaob and Koror.

Waters surrounding the Rock Islands are difficult to navigate, and the terrain can be dangerous. Anyone not bloodied by the razor-sharp limestone will at least leave the Rock Islands very itchy, either as a result of the the poison tree (Semecarpus venenosus, a more potent relative of poison ivy) or chiggers. Because of these dangers and annoyances, the Rock Islands are mostly uninhabited, seldom visited, and show few signs of human impact.

A recent discovery of skeletons in Rock Island caves has stirred a debate over the history of human settlement in Palau. A National Geographic report and TV special were based on the theory that an ancient race of small-bodied humans inhabited the Rock Islands. Although that theory has been discredited, the identity, age, and origin of the skeletons remains a mystery.

The Rock Islands were the quarry sites for Rai stones, the giant, circular currency used on the the Micronesian island of Yap. Beginning more than 600 years ago, Rai stones weighing up to four metric tons were carved from Rock Island limestone. Using a system of bamboo rafts towed by canoes, the stones were carried to Yap, about 500 km away. We saw several quarry sites as we explored the Rock Islands.

Some of the Rock Islands were used as encampments or refueling stations for the Japanese miltary during World War II. Oil drums and other rusting military hardware remain hidden in the caves and crevices.

Today the terrestrial Rock Island habitats are rarely visited, except by the occasional hunter in search of mangrove crabs or fruit bats. In sharp contrast, the marine environments are teeming with visitors. Tourists flock to the beaches, reefs, lagoons, and shipwrecks for world-class diving and snorkeling.

Many of the larger Rock Islands have enclosed pools of salt water called marine lakes. Some unique species have evolved in these miniature ecosystems, isolated from the surrounding ocean. The most famous of these is a species of jellyfish that has a much weaker sting than the jellyfish found in the open ocean. Jellyfish Lake, one of Palau’s most popular tourist attractions, provides an opportunity to swim with jellyfish without the risk of being stung.

Another popular destination is a Rock Island lagoon called the Milky Way. The bottom of the lagoon is a white, sulfur-smelling, silty mud that is used for expensive mud baths and beauty treatments.