Climate change and forests in the Western Ghats

R. Sukumar

Centre for Ecological SciencesIndian Institute of Science

Bangalore, India

Forest cover of India

Source:

Forest Survey

Of India

Temperature

ChangeRainfall

Projections

Source: IITM, Pune

Had RM3 climate projectionsB2 scenario

Predicted change in temperature (Predicted change in temperature (°°C) C)

by 2085by 2085

Predicted change in rainfall (mm) Predicted change in rainfall (mm)

by 2085by 2085

Models of climate change impacts on

vegetation

• Empirical-statistical models have limitations in

that they do not account for plant physiological

responses to changes in CO2, nutrient cycling and

transient responses to climate change

• Process-based models such as BIOME and

HYBRID incorporate complex interactions but are

extremely data intensive, and in certain regions

fail to predict the prevailing vegetation types

CLIMATE DATA FOR BIOME

Model used: Hadley Centre Regional Model; Had RM3

Mean monthly temp. & rainfall, cloud cover

Scale: 0.44 x 0.44 degree RCM grid

Scenarios: SRES; A2 and B2

Period: 2071-2100 mid period: 2085

Observed Climate data: CRU data set for 1901-1995 from East Anglia (0.5x0.5 degree grid)

Projected impact of CC on vegetation

(B-2 scenario) using BIOME

About 75% of India’s forests are projected to change in character

irrespective of the nature of change by the end of the century

Source: Ravindranath, Joshi, Sukumar & Saxena, 2006. Curr. Sci.

Potential Impacts of Climate Change

on vegetation in the Nilgiris using an

empirical-statistical modelVeg type Baseline

Area

Most likely

scenario 2020

Most likely

scenario 2050

Worst case

scenario 2050

Evergreen forest 585 664(+13.4%) 714(+22%) 563(-3.7%)

Moist Deciduous

forest

895 1021(+14%) 1136(+26.9%) 1046(+16.8%)

Dry Deciduous

Forest

1624 1179(-27.4%) 1031(-36.4%) 850(-47.7%)

Dry Thorn Forest 2083 2350(+12.8%) 2339(+12.3%) 2767)+32.9%)

Montane/Grassland 289 280(-3.1%) 268(-7.3%) 263(-9.1%)

Note:- Areas are in sq.km.

Likely vegetation changes in the

Nilgiris

• With the most likely

scenario, there is an

increase in evergreen,

moist deciduous and

dry thorn forest types

and a decline in the

montane forest &

grassland and dry

deciduous forest.

Higher elevations (>1800 m) of the Western Ghats in southern India feature stunted montane forest (shola) and grasslands that are likely to be highly sensitive to global warming

Theories on origin of montane grasslands

• C.R. Ranganathan (1938)

- grasslands in the higher altitudes of Nilgiris are climatic climax

- frost prevents regeneration/survival of seedlings of shola trees

• N. L. Bor (1938)

- pastoralists such as Todas have cleared the shola forests which once covered the entire plateau

- grasslands today are maintained by regular burning

The valleys have peat bogs that preserve the vegetational and climatic record of the late Quaternary (40,000 yr BP and earlier)

Sukumar, Ramesh, Pant & Rajagopalan, Nature 1993

LGMHol.OptArid

Past climate change as recorded in peat bogs in the Nilgiris

Can the Nilgiri tahr survive change ?

• Montane grasslands in the WG are the only habitats of the Nilgiri tahr.

• Enhanced CO2 could fertilize the growth of C3 plants such as the exotic wattles.

• Warmer temperatures could likewise facilitate the spread of woody plants including the invasive wattle and scotch broom

• Grasslands could further reduce with adverse consequences for the tahr and montane species.

Long-term study of dynamics of tropical dry forest Location of the Mudumalai Forest Dynamics Plot

Mudumalai Forest Dynamics Plot

•A 50 ha permanent plot was set up during 1988-89 in

the tropical dry deciduous forests of Mudumalai

Reserve (elevation c.900 m asl) in southern India

•This dry forest plot is a partner in the international

network of large-scale plots coordinated by the

Smithsonian Institution

•Annual enumeration for recruitment and mortality;

growth recorded every four years

•There were c.26000 individuals (stems >1 cm dbh)

from 72 species during 1988; abundant trees are

Lagerstroemia microcarpa, Tectona grandis,

Terminalia crenulata and Anogeissus latifolia

Topography of the Mudumalai FDP

Dry season ground fire in Mudumalai

Environmental variation at Mudumalai

0

200

400

600

800

1000

1200

1400

1600

1800

2000R

ainf

all (

mm

)

Year

rainfall Mean rainfall

0

10

20

30

40

50

60

70

80

90

100

% a

rea

burn

t

Year

Area unburnt Area burnt

Normal rain

Three fires

Low rain

One fire

>Normal rain

No fire

Drought

One fire

Excess rain

No fire

Mortality and recruitment (1989 – 2008)

Importance of long-term research!

0

5

10

15

20

25

30

35

40

45

50

Pe

rce

nt

Year

Mortality

Recruitment

Biomass changes over time

(woody stems >1 cm dbh)

5000

6000

7000

8000

9000

10000

11000

1988 1992 1996 2000 2004 2008

To

tal b

iom

ass (

ton

s)

Census year

Non-wood

Wood

Resilience of Tropical Dry Forests

• 1) Tropical dry forests (that constitute about

2/3 of India’s forest cover) have intrinsic

resilience to climatic variability in the face

of disturbances such as drought and fire.

Carbon stocks increased in spite of stress.

• 2) In this respect the Tropical Dry Forests

may be different from Tropical Moist

Forests that are highly sensitive to such

environmental stresses.

How to Green India?

• Prime Minister has announced

an ambitious programme of

“Green India” with 6 million

ha to be afforested in 5 years

• Climate change considerations

have to be integrated with this

effort if we are to promote

adaptation

• Greening is not just about

planting trees but also about

WHAT to plant and WHERE

to plant

• Planting to facilitate migration

Providing Corridors at Landscape Scales

• Both plant and animal species

need to adapt through

migration along latitudinal

and altitudinal gradients

• Habitat fragmentation would

be a constraint to migration,

especially in species with

limited dispersal abilities

• “Corridors” across large

landscapes are needed for

effective dispersal and

establishment of species

Corridors across the Nilgiri-Mysore

Elephant Landscape in S. India

* Bangalore

Protected Area Network

• India has nearly 600 Protected

Areas (National Parks/Sanctuaries)

• These perhaps offer the best

insurance for adaptation to CC

because diverse forests/ecosystems

are more likely to have species that

have climate tolerance

• Need to redesign Protected Areas

taking into consideration possible

changes in ecosystem structure and

function as a result of future

climate change

Network of

long-term ecological observatories

• Need to set up a number of ecological

observatories at representative sites of the

different biomes in the country (e.g. W. and E.

Himalaya, Mangroves, Island ecosystems, Arid

zone, Western Ghats, Central India)

• Hierarchy of studies from the ecophysiology of

individual species to community-level and

landscape level monitoring using remote sensing

through multi-institutional collaboration