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

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Settlements/ Homestead Veg.Wetland grassMangrove

Fallow land

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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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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