Island Ecosystem and Vegetation Dynamics before and after the 2000-Year Eruption on Miyake-jima Island, Japan, with Implications for Conservation of the Island’s Ecosystem

抄録

　An active volcano, Mt. Oyama in Miyake-jima Island of the Izu Islands, Japan, erupted in 2000, and all the inhabitants were evacuated from the island. A new crater was formed, and since then, a large quantity of volcanic gas containing high concentrations of SO₂ and H₂S has been emitted. Indigenous plants and animals of the island have been heavily damaged by the volcanic deposits and gas. In this paper, we introduce the terrestrial ecosystem of Miyake-jima Island before the 2000 eruption, and then describe the damage to and recovery of vegetation after the eruption, with implications for restoration of the island’s ecosystem. The damage to vegetation was extensive around the summit area, where some indigenous plant species may be extinct. The damage decreased at more distant sites from the crater. In 2001, damaged areas gradually extended toward the eastern leeward side, which was more frequently exposed to volcanic gas, while recovery of vegetation was observed on the northern side where volcanic ash was heavily deposited soon after the eruption of 2000 but was relatively less influenced by poisonous gas thereafter. The important process of vegetation recovery in damaged forests is stem sprouting shown by completely defoliated trees. On Miyake-jima Island, many engineering works (e.g., check dam construction and revegetation work) have already been underway, on demand for improvement of island’s security. Such construction, on the other hand, is likely to influence the island’s ecosystem. We propose that restoration programs should be established considering utilization as well as conservation of the indigenous nature.