Micronesia encompasses some 161 islands strung across the western Pacific near New Guinea. Stretching across more than 27 degrees of latitude and 44 of longitude, the constituent land masses ---including coral atolls and volcanoes --- are diverse geologically, climatically and ecologically. The steepest and wettest of the islands, such as Pohnpei and Kosrae, feature tumbling rivers, often broken with waterfalls, that are some of Micronesia's most sought-after natural attractions.
The largest of the Micronesian islands is Pohnpei, which reaches 2,595 feet in its interior highlands---the greatest elevation in the archipelago. Precipitation in the mountains is high---up to 838cm per year---and feeds over 40 rivers falling to the coast. Those streams create a number of waterfalls in their negotiation of Pohnpei's steep gradient, including Sahwartik and Liduduhnlap falls, some of which are popular hiking destinations.
A 2007 study by four scientists based in Palau, Australia and the United States showed significant sedimentation at the mouth of the Enipein watershed on Pohnpei. The river empties into a lagoon bounded by a barrier reef, and a good proportion of the alluvial sediments remain near the mouth. The researchers observed lower biodiversity and mud-choked habitats in the coral reefs nearest the head of the lagoon. The 10-square-mile Enipein, which features outstanding biodiversity and habitat variety, has witnessed an upsurge in road construction and logging associated with development and plantations. Landslides have increased in the watershed, which, coupled with these human activities, results in greater sediment discharge in the rivers. Fluctuations in rainfall are rapidly mirrored by streamflow in the Enipein basin.
Kosrae is the easternmost of the Caroline Islands and the second-largest in Micronesia; like Pohnpei, its mountainous terrain induces impressive precipitation---over 200 inches of rain a year---and is swathed in rainforests. The Finkol River drains 2,064-foot Mount Finkol, Kosrae's highest point and popular with trekkers.
Fringing some of the Micronesian estuaries and lagoons, especially parts of the Caroline and Gilbert islands, are mangrove swamps. Reflecting the broad geographic extent of the archipelago, individual mangrove species within these swamps varies across the region, with greatest diversity in the Belau islands of the Western Carolines. A mangrove swamp envelops a major confluence in the Enipein watershed above its coastal lagoon; within the basin is the Epinein Marine Park and Mangrove Sanctuary. The mouths of the Finkol, Menka and Falwe rivers also support extensive mangrove forests.