Climate change impact on the Sundarbans - …cdn.cseindia.org/userfiles/presentation1_sundarbans.pdfBlock in Sundarban Percentage of Suitability Very Good Good Poor 31. Impact on tigers.

Climate change impact on the Sundarbans

Nandan MukherjeeCenter for Climate Change and Environmental Research (C3ER)

BRAC University

Physical setting

The Sundarbans appears deep greenAgricultural lands are lighter greenTowns appear as tanStreams are blue

• Part of GBM delta, spanning about 350 km in width in Southern Bangladesh and the state of West Bengal in India

• Within this geographical area, forests cover nearly 10,000 sq km, of which about 6,000 sq km are in Bangladesh:• Total land area is 4,143 km² • Water area of 1,874 km²

• Home to a large human population: 4.5 million in India, 7.5 million in Bangladesh

(Source: WWF, 2010)

Sundarbans: The Eco-region is both Unique and Uniquely Fragile!

Unique because:• Most extensive mangrove forests

exposed to freshwater and seawater mix.

• Most significant strongholds of the Royal Bengal Tiger, an endangered species.

• The flora of the Sundarbans, the mangrove, presents a natural buffer, a bulwark against coastal erosion and seawater ingress into one of the most densely populated regions of the world.

Sundarbans: The Eco-region is both Unique and Uniquely Fragile!

Sundarbans' fragility stems from its uniqueness. • Fragility due to rich ecological diversity, unique biota

comprising :– 334 species of plants, 49 species of mammals, 400

species of fish, 320 species of birds, 53 species of reptiles, 11 amphibian species

– Numerous invertebrates, phytoplankton, fungi, bacteria, zooplankton, benthic invertebrates, mollusks.

• Human induced climate change threatens the delicate balance between land, air, and sea (WWF, 2010)

Fragility due to rich ecological diversity, unique biota comprising :

OBSERVED EVIDENCES OF CLIMATE CHANGE

• Temperature is showing an increasing trend, as well as precipitation

• Variability in the climatic parameters has been increased

Trend in Temperature

Trend in Rainfall

Variability in Temperature• Annual count of summer days

(>25°C) is increasing (J,S,K)• Monthly maximum value of daily

minimum temperature is increasing(S)

• Monthly minimum value of dailyminimum temperature is decreasing(K)

• Percentage of cool night and daysare decreasing (J)

• Percentage of warm days and warmspell duration is increasing (J)

• Cold spell duration is decreasing (J)• Diurnal temperature variability

(range) is increasing (J)

Variability in Rainfall• Annual total wet-day

precipitation is increasing(J,K)

• Number of heavy (>10 mm)precipitation days increasing(J,K)

• Number of very heavyprecipitation (>20 mm) daysincreasing (J,S)

• Annual count of days whenRainfall>5mm is increasing (K)

• Consecutive dry days aredecreasing (K)

Relationship between climate change and hydro-meterologyand hydro

GHG increases

Increases in radiative forcings

Increases in temperature

Changes in precipitation and

ET

Changes in soil moisture

Changes in soil groundwater

Changes in drought

Changes in runoff

Snow and ice melt

Sea level rise Backwater effect by tidal flow

Changes in floodChanges in river flow

Increases in

Increases in

Changes in

ET

Changes in soil

Changes in soil

drought

Salinity intrusion

Storm surge

Snow and ice melt

Sea level rise

EFFECTS OF CLIMATE CHANGE

•Increased occurrence of storm surge in the Bay of Bengal•Increased tidal flooding and permanent inundation•Increase in salinity, and change in water quality

EFFECTS OF CLIMATE CHANGE

Tropical Cyclone : some facts

Although science is not conclusive, IWTC (2006) noted that:

• If projected rise in sea level due to global warming occurs, then the vulnerability to tropical cyclone storm surge flooding would increase

• Some increase in cyclone peak wind speed and rainfall will occur if climate continues to warm

• Model studies and theory project a 3-5% increase in wind speed per degree Celsius increase of sea surface temperature.

Cyclone Sidr-It was never anticipated before

Source:http://cimss.ssec.wisc.edu/goes/blog/wp-content/uploads/2007/11/071115_sidr_mimic_anim.gif

Composite Track of Cyclones in Bay of Bengal

1961-1990 2071-2100

(Unnikrishnan, 2009)

Frequency Distribution of Cyclones in Bay of Bengal

1961-1990

2070-2100

Damage done by SIDR: A Preliminary Assessment

• Cyclone Sidr struck Bangladesh with winds of over 220 km/h (150mph) and a tidal surge of > 6m

• The authorities confirmed at least 2,3001 deaths.

• An estimated one million families are thought to have been affected.

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

Damage done by SIDR: A Preliminary Assessment

Effects on Fauna:• 40 species of mammals, • 400 species of birds and• More than 200 species of fishes fell victim to

the calamity.

SEA LEVEL RISE AND TIDAL FLOODING

Historic WL rise in Sundarbansand adjacent area

Coastal flooding

Slide 22

Year 2030 Year 2050

Sundarbans and Coastal District

Flood/ Inundation Analysis

DECREASING FRESH WATER INFLOW AND SALINITY INTRUSION

Situation of Gorai• After the construction of

Farakka, dry seasonal flow in the Gorai River has reduced drastically.

• Mean dry seasonal flow decreased 72% and it has increase by 23% after the GWT

• Mean 1-day low flow has been decreased from 146 cumec to to 51 cumec

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 SLR0 SLR0 SLR32 cm SLR32 cm SLR32 cm SLR88 cm SLR88 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

EFFECT OF CLIMATE CHANGE ON BIODIVERSITY

Changing Pattern in Distribution of Sundri and Gewa from 1992 to 2001

29

Changing Pattern in Distribution of Goran and Gewa from 1992 to 2001

30

Plant Type – Sundari – Health Index Under Different SLR Scenarios

Suitability of Sundri in SLR Base scenario

0

20

40

60

80

100

Block_A Block_B Block_C

Block in Sundarban

Perc

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Very Good Good Poor

Suitability of Sundri in SLR 32 cm scenario

0

20

40

60

80

100

Block_A Block_B Block_C

Block in Sundarban

Perc

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f Sui

tabi

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Very Good Good Poor

Suitability of Sundri in SLR 88 cm scenario

0

20

40

60

80

100

Block_A Block_B Block_C

Block in Sundarban

Perc

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Very Good Good Poor

31

Impact on tigers

Sea level rise (cm) (baseline is year 2000)

High tiger abundance habitat (km2)

Medium tiger abundance habitat (km2)

Low tiger abundance habitat (km2)

Total tiger habitat (km2)

0 574 1,445 2,155 4,1754 574 1,442 2,153 4,1698 551 1,352 2,117 4,021

12 527 1,229 1,941 3,69716 458 1,011 1,477 2,94620 309 622 840 1,77124 142 236 296 67428 37 74 48 159

Impact on tigers

No SLR 28 cm SLR

HOW TO SAVE THE SUNDARBANS: A TECHNICAL SOLUTION

Importance of Ganges-Gorai System

• Due to a drastic fall in the flow of the Gorai River, at least seven of the 15 rivers dependent on it, are now nearly dead while eight others are flowing timidly.

• The Gorai River normally has about 15 per cent of the Padma River’s annual flow volume. To keep the GoraiRiver bankful about 5 000 cum/sec flow will be required (BWDB 2000).

• So a minimum flow of about 2 000 cum/sec in the Gorai River and 13 334 cum/sec in the Ganges River, is necessary for fresh water inflows to the Sundarbans.

Proposed Ganges Barrage

Diversion flows down the Gorai River during the dry season could be made at 4 500 cum/s

How to combat the situation

• Integrated coastal and marine management• Monitoring the impact of climate change on

coral reef, Royal Bengal Tiger, crocodiles and Sundari tree

• Coastal vulnerability and risk assessment• Economic valuation of Sundarbans' resources • Afforestation and reforestation by salt tolerant

species

How to combat the situation

• Facilitating natural regeneration and natural succession of native tree species

• Creating public awareness through mass media• Initiating community based coastal forestation• Protecting existing mangroves against encroachment

and cutting• Establishing mechanisms to harness benefit from

Global Carbon Market

Thanks

Lets save the Sundarbans and the Tigers