The purpose of this study was to understand the changes in mangrove forests in the catchment basin of the Nakara River in Iriomote Island during the period from 1972 to 2003. This study revealed that the mangrove forests expanded their habitats in the landward and riverside areas of the river, as well as to the shoal where sand tends to accumulates easily. Specifically, in the middle area between the downriver and upriver areas, a tendency towards an increase in mangrove habitats was seen in the lower river region, and there was a new emergence of this trend in the upper river region. It is speculated that the expansion of mangrove forests to the landward area may be partly due to a wider landward area with a moderate incline, and rise in sea level. In addition, the investigation into change in mangrove forests related to species growing in the study area suggests that human pressure, such as the use of mangroves as construction materials prior to the designation of this area as a national park, may have had an effect on the differences in species growing there.
