By Carl Lewis, September 19, 2008
Over the past three days we found palms in many of the accessible lowland and middle-elevation sites on Kosrae. The jagged ridges and peaks were inaccessible, but we were able to spot large numbers of palms from below. Once we learned to recognize the bright white flowering stalks of Ponapea ledermanniana from a distance, we began to see them all over the island.
Ponapea is abundant on Kosrae. We estimate that there are more than 1,000 mature individuals and many more juvenile palms. They grow at all elevations, from lowland swamps to the high peaks and ridges. However, there are real threats to the survival of Ponapea ledermanniana on the island. Kosrae is small (110 square kilometers), so any of these threats could impact the entire island quickly.
Ponapea ledermanniana surrounded by invasive Merremia peltata and Costus speciosus
Competition from invasive species
We found two highly aggressive invasive species in Ponapea habitat. Merremia peltata is an invasive vine that appears to be sprawling over the island’s natural forests. We saw it blanketing an area with mature Ponapea palms, which is likely to limit regeneration. We also saw it climbing to the top of tall palms, where it may interfere with flowering and leaf development. The invasive ginger Costus speciosus grows throughout Kosrae, including the habitats of Ponapea. It grows in thick masses that have the potential to prevent growth of palm seedlings.
Small-scale farming
Today we found a patch of untouched forest with a healthy population of Ponapea, including many adults and seedlings. In an adjacent farmland we found some tall Ponapea palms that had been left in place when the farmer cleared the land. Although they were fruiting normally, we found no seedling palms among the pioneer shrubs and vines that had colonized the farmland. It is unlikely that the cleared land will become suitable palm habitat in the foreseeable future. We can expect that the expansion of farming on Kosrae will continue to degrade palm habitat.
Threat of natural disasters
Kosrae is outside the normal path of Pacific typhoons, but it still has the potential to be hit infrequently. A typhoon could have a disastrous impact on the natural forest, leveling trees and paving the way for invasive species. It is conceivable that a single large storm could wipe out all suitable Ponapea habitat on Kosrae.
Tomorrow we fly to Pohnpei, the other location for Ponapea ledermanniana, to develop a complete conservation assessment for the species. We will work with conservation agencies on both islands to produce species management plans.
