biodiversity, floristic composition and climate change in the sundarbans
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Biodiversity, Floristic Composition and Climate Change in
the Sunderbans
Presented byIstiak Sobhan
April 8, 2023
The Sundarbans
•Area over BD+IND 10,000 km2
•Roughly 60% fall in BD
•Located in the SW part of the country between latitudes 89000/ and 89055/ E and longitudes 21030/ and 23030/N.
•Total area in BD part of SRF is 577,356 ha of which 175,724 ha is water.
Biodiversity3 Protected Areas in Sundarban Reserved Forests (SRF), which constitute the core area of the World Heritage Site, inscribed in 1997. SRF is the 1st Ramsar site of the country.
The total area of the 798th World Heritage Site is about 1,400 km2, of which 490 km2 is water, carrying a very rich biodiversity of flora and fauna.
400 species of fish and crustacean275 species of birds
incl 95 waterfowl42 species of mammal50 species of reptiles
8 species of amphibians25 species of mangroves
Factors influence biodiversity
• Water resources• People living around• Landuse in and around the forest• Elevation• Salinity (soil & water)• Natural disaster (Cyclone) • Sedimentation
Major river systems• Ichhamati-Jamuna system• Benta-Kobadak- Kholpetua
- Arpangasia system • Kobadak sub system• Sibsha system• Gorai- Rupsha - Pussur
System• Sela gang system• Bhairab subsystem• Madhumati-Baleswar
system• Chitra subsystem
Demography
• Consists of the three districts Bagerhat, Khulna and Satkhira.
• The districts cover a total area of 10,660 sq. km.
• Dependent population mainly in the northern part is about six million (6m).
Livelihood• Variety of NTFP
such as fish, honey, wax, nypa leaves, etc. are collected by the inhabitants.
• Also gather climbers, grasses, medicinal herbs, etc.
• The 12,000 Km of rivers and creeks produces large quantities of fish, shrimps, crabs, oysters, etc.
Broadly 17 SRF-adjoining Upazilas, considered as impact zone (SIZ), a band extending 20 km outside the SRF boundary (Popn 1.84m)
Cropping Pattern Map
Kalaroa
Tala
Debhata
Dumuria
Paikgacha
Kaliganj
Assasuni
Batiaghata
Terokhada
Mongla
RampalDacope
Shyamnagar
Koyra
Fakirhat
Rupsa
PhultalaDighalia
Bagerhat Sadar
Satkhira Sadar
Sarankhola
Morrelganj
Chitalmari
Mollarhat
Kachua
River/Beels
Settlements/ Homestead Veg.Wetland grassMangrove
Fallow land
Till/Other T.Aman Fallow
Fallow Fallow Boro
Bagda Fallow Bagda
Fallow T.Aman Fallow
Fallow T.Aman Rabi(Pulses)
Fallow T.Aman Boro
Bagda T.Aman Bagda
Till/Other T.Aman Rabi (Other winter crops)
Golda Golda Boro Golda Golda Golda
Sundarbans Boundary
Ground Elevation
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Heavy Siltation
Slow Slitation
Moderate Siltation
River Siltation in Southwest Region
1973
2000
Total 70,000 ha cultivable land affected by salinity in Khulna and Jessore.
Soil salinity of 1973 & 2000
Water salinity
Slide 12
Cyclone
More than 40% cyclones over the last 100 yrs crossed through the Sundarbans.
Profile of vegetation along the geomorphic gradient
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L o w -tid e w a te r lev e l
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Historical changes in vegetation
• Geological evidences suggest that the Bengal Basin tilted eastward during the 12th Century because of the neo-tectonic movement (Morgan and McIntire, 1959).
• The lack of freshwater to the western part has had significant effects on the floristic composition of the forests. For instance, according to some studies of fossil pollen, Heritiera fomes was a dominant arborescent species in the Calcutta region about 5000 years ago (Blasco, 1975).
• The Indian Sundarbans as well as the western part of the Bangladesh Sundarbans no longer support a healthy population of this species.
Changes in floristic
composition
Matrix of changes
Year 1982
Year 1995 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 20
0 1 608 134 4 11 3 1 70 2 1 3 2 2 111 806 3 3 29 13 221 1 1 1 4 7 5 1 3 2 2 17 1 4 4 1 57 3 1 5 1 22 1 108 7 28 1 4 12 7 1 6 10 25 275 14 3 37 3 4 1 7 1 22 78 1 40 13 421 4 2 2 8 4 1 8 3 56 18 2 5 9 1 4 35 4 22 497 1 1 7 1
10 1 1 5 1 11 1 1 1 1 13 12 1 3 2 2 13 1 1 1 1 28 2 1 14 1 5 2 1 2 1 13 17 2 15 1 1 1 1 20 2 1 1
Class code Description 0 Water 1 Sundari 2 Sundari-Gewa 3 Sundari-Passur 4 Sundari-Passur-Kankra 5 Gewa and Gewa-Mathal (Coppice) 6 Gewa-Goran 7 Gewa-Sundari 8 Goran 9 Goran-Gewa 10 Passur-Kankra 11 Passur-Kankra-Baen 12 Baen 13 Keora 14 Grass and Bare Ground 15 Tree Plantation 20 Sandbar
Changes in areaVegetation communities 1995 1982 Difference % area of 82
remaining unchanged in 95
% area of 95 remaining
unchanged from 82
Water 4.46 4.46
Sundari 750.30 836.50 -86.20 72.70 81.05
Sundari-Gewa 1061.70 1208.29 -146.59 66.70 75.91
Sundari-Passur 24.71 21.84 2.88 77.40 68.39
Sundari-Passur-Kankra 73.94 67.32 6.63 85.18 77.54
Gewa and Gewa-Mathal (Coppice) 213.86 193.40 20.46 56.05 50.69
Gewa-Goran 348.96 373.70 -24.74 73.52 78.74
Gewa-Sundari 764.83 597.97 166.86 70.44 55.07
Goran 83.34 85.50 -2.16 65.35 67.04
Goran-Gewa 563.70 571.87 -8.17 86.87 88.13
Passur-Kankra 2.86 9.55 -6.70 15.65 52.36
Passur-Kankra-Baen 25.85 16.77 9.08 78.29 50.80
Baen 11.47 9.28 2.19 32.48 26.28
Keora 79.32 36.61 42.71 75.62 34.91
Grass and Bare Ground 58.91 43.68 15.23 38.63 28.64
Tree Plantation 2.10 3.52 -1.42 31.20 52.26
Sandbar 9.45 3.97 5.49 26.54 11.14
Historic WL rise in Sundarbans and adjacent area
NDVI, Satellite Aqua, 20th November 2007Resolution is 250 m
Forest Area Affected by cyclone SIDR
Affected area is 21% Of total Sundarbans area
Forest affected areas in the Sundarbans
Mean Temperature and Trend
National mean shows 0.3 0C increase over the 40 years.
SLR Trends in different points of Bangladesh
3.9 mm/yr
1.4 mm/yr
5.6 mm/yr
Coastal flooding
Slide 23
Year 2030 Year 2050
Sundarbans and Coastal District
Flood/ Inundation Analysis
Line of equal salinity (5 ppt) for different sea level rise in dry season
0 SLR32 cm SLR88 cm SLR
0 SLR32 cm SLR88 cm SLR
0 SLR32 cm SLR88 cm SLR
0 SLR32 cm SLR88 cm SLR
in base condition with SLR 32 cm with SLR 88 cm
Condition Salinity (ppt)
0-1 ppt 1-5 ppt 5-10 ppt 10-15 ppt 15-20 ppt 20-25 ppt > 25 ppt
Base condition 10.8% 16.2% 19.1% 20.9% 15.9% 12.6% 4.5%
SLR 32 cm 9.2% 17.8% 18.0% 18.6% 15.6% 15.7% 5.0%
SLR 88 cm 4.0% 21.0% 17.8% 15.6% 14.9% 17.9% 8.8%
Salinity distribution in different scenario
Factor by which annual sedimentation rate changes due to sea-level rise
SLR: 14 cm SLR: 32 cm
SLR: 88 cm
S_mm_88cm_interpol0 - 1.1771.177 - 2.3542.354 - 3.5323.532 - 4.7094.709 - 5.8865.886 - 7.0637.063 - 8.2418.241 - 9.4189.418 - 10.595No Data
Moe_bnd.shp
< 0.75
0.75 – 1.0
1.0 - 2.0
Factor of change
> 2.0
Scenario SLR 14 cm SLR 32 cm SLR 88 cmAdditional areas of sedimentation (km2) 243 448 726
Cropping pattern in SIA under SLR condition
Thank YouAcknowledgement: CEGIS, IWM, IWFM, BCAS, CDMP, FD, RIMS and IUCN
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