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Conservation strategies in coastal wetland: compromise based on habitat conflicts between mangroves and the fiddler c
rab, Uca formosensis in Taiwan
Hwey-Lian Hsieh, Po-Fen Lin*, Chang-Po Chen
Institute of Zoology, Academia Sinica, Taipei, Taiwan
Research Center for Biodiversity, Academia Sinica, Taipei, Taiwan
Outline
1. Taiwanese fiddler crab, Uca formosensis.
2. Why mangrove is important to Taiwan coastal zone?
3. The habitat characteristics of mangroves and Uca formosensis.
4. How mangroves could change the habitat of Uca formosensis?
5. Conservation Strategies
IntroductionThe fiddler crab Uca formosensis is endemic to Taiwan
Uca formosensis Other Uca species
The habitats of Uca formosensis : Non-vegetated, high tidal zones in firm mud intertidal flats
Life history stageZoea and Megalop stageSpread/distribution
Juvenile
Feeding/growth
Adult
Burrowing/breeding
Competition between fauna
Aspect of organism
Micro- habitat
Temperature, humidity, sediment salinity, oxygen content, water content, quantity and quality of food, toxic materials, etc.
Coastal environments
erosion/siltationemerging/sinking
Macro- habitat
support
Aspect of habitat
Sediment
particle sizetopographyelevation
mangrovebenthic microalga
e
VegetationWater influence
estuarytideflow tidal level
Water column
influence
influence
Benthic environment
Benthic environment
120°E 121°E 122°E
25°N
24°N
23°N
23°N
Distributional records of Uca formosensis (from 1918 to 1997)
Black stars represent areas with active population of U. formosensis
Open stars represent areas where the population of U. formosensis has extinguished.
(Shih,1999)
Threats to fiddler crabs: Land reclamation, dike and road construction
Another threat to fiddler crabs: Improper planting of mangroves on the Uca formosensis habitats
Goals of this study: To examine the habitat characteristics of bot
h U. formosensis and mangroves To provide a scientific basis for conserving t
he diversity of intertidal habitats and populations of U. formosensis
To propose conservation strategies for the protection of intertidal habitats in coastal wetlands of Taiwan
Material and Methods
Hsinchu City
Taipei City
Changhua County
Kuantu (KT)
Tachuang mangrove (TCS)
Haishanku Mangrove (HS)
Tatu (TT)
Jenchang Lake (JCL)
Tachuang Creek North Shore (TCN)
Haishanku-1(HSI)
Haishanku-2(HSII)
Haishanku-3(HSIII)
Sedimentary substrates of microhabitats Grain size (Silt/Clay content) Total organic carbon and nitrogen content Water content pH Salinity of interstitial water Depth of the oxidation layer Benthic macroinvertebrates
Depth of the oxidation layer
JCL TCN HS I HSII HSIII DD HS TCS GD
Silt
/Cla
y C
on
ten
t(%
)
0
20
40
60
80
100
Results and Discussion
○ The habitat of Uca formosensis (△mean±S.E.) ● The habitat of mangroves(▲mean±S.E.)
TTJCL TCN HSI HSII HSIII HS TCS KT JCL TCN HS I HSII HSIII DD HS TCS GDD
ep
th o
f O
xid
ati
on
La
yer(
cm
)0
10
20
30
40
50
60
70
TTJCL TCN HSI HSII HSIII HS TCS KT
JCL TCN HS I HSII HSIII DD HS TCS GD
Wat
er C
on
ten
t(%
)
0
10
20
30
40
50
JCL TCN HS I HSII HSIII DD HS TCS GD
pH
0
2
4
6
8
10
○ The habitat of Uca formosensis (△mean±S.E.) ● The habitat of mangroves(▲mean±S.E.)
TTJCL TCN HSI HSII HSIII HS TCS KT TTJCL TCN HSI HSII HSIII HS TCS KT
JCL TCN HS I HSII HSIII DD HS TCS GD
TN
(%)
0.00
0.02
0.04
0.06
0.08
0.10
0.12
0.14
0.16
0.18
0.20
JCL TCN HS I HSII HSIII DD HS TCS GD
TO
C(%
)
0.0
0.5
1.0
1.5
2.0
2.5
3.0
TTJCL TCN HSI HSII HSIII HS TCS KT TTJCL TCN HSI HSII HSIII HS TCS KT
JCL TCN HS I HS II HS III TT HS TCS KT
Den
sity
of
infa
un
al c
om
mu
nit
y (i
nd
ivid
ual
s/m
2 )
0
5000
10000
15000
20000
25000
○ The habitat of Uca formosensis (mean±S.E.) (including polychaetes, insects and crabs )
● The habitat of mangroves (mean±S.E.) (including polychaetes, insects, crabs and oil
gocheates)
Potential negative impacts on U. formosensis caused by mangrove intrusion
A. Alternation of sediment characteristics
Siltation increases
Depth of oxidation layer decreases
pH decreases
B. Direct effects by mangrove trees Shading effects (Hsieh,1999; Hsieh et al.,2002; Wainright et al., 2000)
Productivity of benthic microalgae declines
Aboveground structures Stems and branches block crabs’ view and movement Leaves shaken by wind may scare crabs
Underground structures Roots become obstacles to crabs’ burrowing
C. Benthos changes (Shih,1999; Hsieh et al.,2002)
Helice formosensis, H. wuana, U. arcuata prefer
mangrove habitats
Helice formosensis U. arcuata
Accelerate studies on the habitat characteristics of each stage of the life history of U. formosensis
Apply ecological engineering practices to restore habitats of U. formosensis
Monitor the impacts of mangroves on estuarine ecosy
stems and manage mangroves accordingly
Conservation Strategies
Conserve coastal wetlands which
1) retain those still sound function,
2) improve those that have been disturbed, and
3) restore those that have been destroyed.
We try to connect these three types of habitats to form a “Coastal Wetlands Conservation Greenway along Taiwan’s Western Coastal Zone” (Hsieh et al., in press)
Promote the wise use of coastal wetlands
Mangrove trees
Uca formosensis reserve
Buffer zones
Mangroves should be eliminated from U. formosensis reserve areas.
For examples: remove mangroves from Uca formosensis reserve and buffer zones
Carry out public education on biodiversity and habitat diversity.
When U. formosensis encounters mangroves
Summary
The invasion of mangroves into U. formosensis habitats has a negative impact on the fiddler crab’s population.
Mangroves on estuarine ecosystems and coastal zones should be managed properly in Taiwan.
Future coastal management should emphasize on maintaining biodiversity and habitat diversity.
Acknowledgements
Funding agencies
Institute of Zoology Academic Sinica
Research Center for Biodiversity Academia Sinica
Hsinchu City Government
Assistants and Graduate studentsYuan-Hsien Chen, Hsin-Yi Yeh, Hsiao-Hui Yang, Tai-An Chen, Song-Lin Wu, Wu-Hsiung Ou, Shu-Ting Lin, Feng-Lin Wang, Chang-Hao Hoa, Ming-Che Yang, Meng-Jeng Guo.
Thanks!
