The effect of a super typhoon to a mangrove forest in Iriomote island

• Project/Area Number: 16K14946
• Research Category: Grant-in-Aid for Challenging Exploratory Research
• Allocation Type: Multi-year Fund
• Research Field: Forest science
• Research Institution: University of the Ryukyus
• Principal Investigator: WATANABE Shin 琉球大学, 熱帯生物圏研究センター, 准教授 (10396608)
• Research Collaborator: MIYAGI Toyohiko ; UCHIYAMA Shoichiro
• Project Period (FY): 2016-04-01 – 2019-03-31
• Project Status: Completed (Fiscal Year 2018)
• Budget Amount: ¥4,160,000 (Direct Cost: ¥3,200,000、Indirect Cost: ¥960,000); Fiscal Year 2018: ¥650,000 (Direct Cost: ¥500,000、Indirect Cost: ¥150,000); Fiscal Year 2017: ¥650,000 (Direct Cost: ¥500,000、Indirect Cost: ¥150,000); Fiscal Year 2016: ¥2,860,000 (Direct Cost: ¥2,200,000、Indirect Cost: ¥660,000)
• Keywords: マングローブ / 大型台風 / ドローン

Outline of Final Research Achievements

In Iriomote island located at south western islands of Japan, we monitored mangrove forest hit by a super typhoon. As the result of the traverse survey, it was found that the ground level of the devastated area was lower by 30 to 50 cm than the ground level covered by mangrove trees. It was also revealed by our flight researches that the devastated area has been growing year and year.
It was thought that the mangrove forest collapse in a fairly large area by typhoons induced soil erosion because the forest floor lost the forest crown to protect from rainfall. At the same time, the complex root system to keep mangrove peat stably from daily inundation was lost. And it was also suggested that the dynamics of large-scale soil degradation and inundation has caused continuous soil erosion, thus the continuous forest degradation has been also induced like domino effect. The changed ground level might not provide suitable ecological niche for the present mangrove species anymore.

Academic Significance and Societal Importance of the Research Achievements

本研究ではドローンと実地調査によるモニタリングを3年間継続し、西表島のマングローブ林が年々大型化する台風の影響で失われ続けている現状を確認し、その崩壊メカニズムを解明した。そしてマングローブ林が失われることにより、大量の土砂が林外へ流出していることも明らかとなり、河口域の汽水生態系と沿岸域珊瑚礁生態系へ及ぼす悪影響が懸念された。また本研究対象のマングローブ林大規模倒壊現象は、70年以上前の太平洋戦争に伴う過度のマングローブ伐採と近年大型化した台風による被害との複合災害であることが示唆された。

Research Products

• [Int'l Joint Research] Sabah Forestry Department(Malaysia)
• [Int'l Joint Research] Sabah Forestry Department(Malaysia)
• [Presentation] Damage by Super Typhoon could be a crucial key to re-establish mangrove forests (2018)
  • Author(s): Shin Watanabe, Shouichiro Uchiyma, Toyohiko Miyagi
  • Organizer: Annual Meeting of Japan Society for Mangroves
  • Invited
• [Presentation] Applying drone into mangrove rehabilitation. (2018)
  • Author(s): Shin Watanabe, Shoichiro Uchiyama, Toyohiko Miyagi, Shigeyuki
  • Organizer: Mangrove symposium, Thailand Forestry Department, Bangkok, Thailand, Aug 23
• [Presentation] A challenge to support mangrove rehabilitation by drone (unmanned aerial vehicle) (2017)
  • Author(s): Shin Watanabe
  • Organizer: International Conference on Sustainable Mangrove Ecosystem 2017（ITTO,UN）
  • Place of Presentation: Inna Grand Bali Beach Hotel, Bali, Indonesia
  • Year and Date: 2017-04-17
  • Int'l Joint Research
• [Presentation] Do you want Bird’s Eye? (2017)
  • Author(s): Shin Watanabe
  • Organizer: The 5th International Symposium on Primatology and Wildlife, The Leading Graduate Program
  • Place of Presentation: Kyoto University, Kyoto, Japan
  • Year and Date: 2017-03-02
  • Int'l Joint Research / Invited
• [Presentation] Super typhoons offer an opportunity for Japanese mangrove forest to regain the ecological niche? (2017)
  • Author(s): Shin Watanabe
  • Organizer: 54th Annual meeting of the Association for Tropical Biology and Conservation
  • Int'l Joint Research