Natural laboratory for marine species

10 July 2014 | Fact sheet

Rock Islands Southern Lagoon, World Heritage site, Palau

Background
Boasting the largest number of marine lakes in the world and a veritable maze of dome-shaped and green islands, Rock Islands seems to float with a supreme majesty in a turquoise lagoon surrounded by stunning coral reef. The Rock Islands Southern Lagoon contains 52 marine lakes, some connected to the sea and others so isolated that unique and endemic species have evolved. The lakes show an outstanding example of how marine ecosystems and communities develop, and make the lakes valuable as ‘natural laboratories’ for scientific study of evolution and speciation. The magnificent golden jellyfish, which can be found in at least five different marine lakes, is a genetically and morphologically distinct subspecie.

As if the marine life were not enough to make this place something of an adventurer’s paradise, archaeological remains and rock art sites can also be found in two island clusters - Ulong and Negmelis, and on three islands - Ngeruktabel, Ngeanges, and Chomedokl. Although currently uninhabited, the islands were once home to Palauan settlements, and Palauans continue to use the area and its resources for cultural and recreational purposes.

View images of the world heritage site
Size and Location
The Rock Islands Southern Lagoon is located in Palau, within Koror State and is a 100,200 ha. marine site.

Flora and Fauna
The Rock Islands Southern Lagoon contains an exceptional variety of habitats within a relatively limited area. Barrier and fringing reefs, channels, tunnels, caves, arches and coves are all on show, as well as the highest number and density of marine lakes in the world. Furthermore, the marine lakes of the property are at different stages of geological and ecological development meaning there is tremendous variety to the species which can be seen. These features represent an outstanding example of how marine ecosystems and communities develop. With low fishing pressure, limited pollution and human impact, as well as an exceptional variety of reef habitat, the resilience of reefs on the property makes it a critical area for protection. It is also an area of crucial importance for climate change adaptation of reef biota, and potentially as a source of larvae for reefs in the region.

The aesthetic beauty of the site is heightened by a complex reef system featuring over 385 coral species and different types of habitat. The corals sustain a large diversity of plants, birds and marine life including dugong and at least 746 species of fish, over 385 species of corals, at least 13 species of sharks and manta rays, 7 species of giant clams, and the endemic nautilus. The forests which grace the islands include all of Palau’s endemic birds, mammals, herpetofauna and nearly half of Palau’s endemic plants.

Challenges
The tourism industry is the largest industry in Palau, sustaining its economy. The number of visitors to Palau during the last decade ranges between 70,000 and 90,000 per year. Tourism is likely to increase over the next decade and increasing the number of visitors to the country is a likely development target. Overall tourism numbers to Koror and RISL need to be managed carefully in order to avoid negative impacts on the environment.

The 1998 mass coral bleaching event severely impacted reefs in Palau, and killed over 30% of corals. The marine lakes were also impacted and elevated temperatures caused the disappearance of jellyfish. However, the event also illustrated the benefits of the complexity of reef habitats to the resilience of RISL.