01 takemura1005en final

INTERNATIONAL SEMINAR ON MARINE TOURISM, SCIENCE AND TECHNOLOGY JAMBOREE,
SAIL SABANG AND THE 4TH INTERNATIONAL WORKSHOP ON SATO UMI, Jakarta, October 5, 2017

Community-based monitoring
toward sustainable
management of mangrove
forest in Okinawa, Japan

Shion TAKEMURA
Japan Fisheries Research & Education Agency

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Background:
Functions of mangrove & Recent situation
Stabilizing coast and river-mouth
-> Natural barrier

Sustaining biodiversity
-> Food supply

Mangroves are declined due to human alterations in the world.
(e.g. conversion to mariculture, agriculture, urbanization and forestry use etc)

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Mangrove forest
in Okinawa Island, southern Japan
Okukubi River

Osaka

Canoeing

Tokyo
Okinawa

Okinawa
Island

20km

 Local community are going to conserve and use
mangrove ecosystem as resource of ecotourism.
 Mangrove is important resource for local economy.
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Life cycle of mangrove forest
seed dispersal

 Tidal current

colonization

 Muddy and
soft soil

germination
&
growth

regeneration
gap creation

mature

 Salinity

 Disturbances

Regeneration of mangrove community is assisted by soft soil and its condition
formed by frequent exchange of sediment at bar surface during flood.
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Takemura et al., (2012)

Degradation of mangrove habitat due to
infrastructure construction in Okukubi River
Narrowed river width

Reduction of discharge

(Bridge construction)

(Dam renewal)

X10
1980

Before
Capacity of reservoir:
818,000m3

After April 2013
Capacity of reservoir:
8,560,000m3

These infrastructures reduce exchanges of sediment at bar surface.
Takemura et al., (2011)

Mangrove habitats were changed to unsuitable for regeneration
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→ Artificial forest management is needed.

Lack of information sharing among stakeholders
Council has been established
(April 2015)

Deforestation
by national government
(April 2015)

SH
 Local ecotourism company
 Local NPO
 Local government
 State government
 National government

Challenges: To share the current situation and the value of mangrove
habitat among stakeholders in order to promote consensus building toward
sustainable forest management.

Objectives: To developed a community-based monitoring system that SH
can grasp changes occurring in mangrove forest by a simple way.

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Method
(1) Smartphone Monitoring

1. Take photo with GPS

Survey protocol
4. Mapping (automatically)

2. Sent email attached photo
5. Check data (classification)

1. Development of survey system
• Web based survey system was
developed using camera and GPS

function of smartphone.

2. Data collection

3. Store database
6. Publish (PC & smartphone)

Osawa et al., (2013) Japanese Journal of Conservation Ecology 18:157-165

• We investigated monitoring surveys
using developed web based system at
January and March 2016.

3. Analysis
• Photos were classified into seedlings,
saplings, dead trees or another
terrestrial plants.
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Method

(2) Bed Level Change Monitoring
1. Survey sites
• 19 survey sites were established in
mangrove forest.
• The initial bed elevation of survey sites
was measured by GNSS (June 2016).
• And PVC pipes were set on the
sediment surface.

Monitoring by canoe instructors

2. Data collection
• Canoe instructors measured and
recorded the length of PVC pipes
exposed from the sediment surface
every month
(June 2012 ~ March 2016).
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Method

(3) Crab Distribution Monitoring
1. Sampling methods

Pitfall traps (Steal can)

• 5 traps were buried flush with the
sediment surface on June, October 2012
and March 2013.
• Traps were checked daily for 3 days
(only Jun 2012 was 2 days).
• At the same time, bed elevation and
substratum were measured at each
survey site.

2. Analysis (Habitat suitable models)
• Distributions of crab species were
related to bed elevation and substratum
using GLMM and GLM.
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Results and Discussion:
(1) Smartphone monitoring

Map of forest situation

Seedlings
Seeds

Forest
degradation

Dead trees

Forest
degradation
(Change
into land)

Terrestrial
Tree species

Forest situations and their locations can be identify and recorded.
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Results and Discussion:
(2) Bed Level Change Monitoring
Location of outer edge in sandbar

Location of sandbar

Outer edge
area

Bed Level Validation (cm)
‫ق‬Erosion or Sedimentation‫ك‬

Bed Level Validation (cm)
‫ق‬Erosion or Sedimentation‫ك‬

Long term patterns of river bed fluctuation

Inner
area

Upper

Lower

Outer edge area: Gradual erosion

Upper area: Erosion

Inner area: Dynamic equilibrium

Lower area: Dynamic equilibrium

Imai et al., (2016) Journal of Japan Society of Civil Engineers, Ser. B1. 72(4): I_1093-I_1098

Long term patterns of river bed fluctuation can be clarified.

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Results and Discussion:
(3) Crab Distribution Monitoring
Crab species by pitfall traps

Biological Indicators in Okukubi River

Habitat Suitable Models

Changes of soil condition can be
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grasp by composition of crab species.

Conclusion and further research
(1) Smartphone Monitoring

Forest

(2) Bed Level Change Monitoring (3) Crab Distribution Monitoring

River Bed

Soil condition

• Our monitoring system allow for stakeholders to monitor the
mangrove forest by themselves.
• Further research is needed to investigate continuous monitoring
and to utilize its results for policy and next actions.
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Thank you very much !!

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