Journal of
Threatened Taxa | www.threatenedtaxa.org | 26 May 2018 | 10(6):
11760–11769
The characteristics, representativeness, function and conservation
importance of tropical dry evergreen forest on Indias Coromandel
Coast
Mark Everard
University of the West of England (UWE Bristol), Coldharbour Ln, Bristol BS16 1QY, UK
mark.everard@uwe.ac.uk
Abstract: The central area of the Coromandel
Coast, southeastern India, has been subject to a very
long history of human habitation and land use change, substantially reducing
the coverage of native forest.
There are polarised views about definitive characteristics of native
tropical dry evergreen forest (TDEF), albeit agreement that the habitat type is
locally characteristic though now severely reduced, fragmented and
degraded. A literature review was
undertaken to determine the evolutionary origins of TDEF as well as its
characteristics. A combination of
both natural and human factors gives rise to TDEF, explaining the heterogeneity
of existing stands even in close proximity to each other. Religious shrines are often associated
with sacred groves, which are influential in the survival of stands of
TDEF. These remaining stands are
highly fragmented across the wider landscape and subject to species invasions
from adjacent habitats as well as increasing human pressures. On the basis of existing evidence, it is
not possible to describe TDEF through a definitive community of tree species,
though typical constituent species are listed. TDEF may therefore be representative of
a larger biome, as for example tropical rainforest, rather than a specific
vegetation type. Nevertheless,
there is general consensus about the importance of restoring TDEF, including
its many associated plant and animal species, many of which have medicinal,
spiritual and other uses and meanings.
Regardless of biological definitions of TDEF, the functions it performs
and the diversity of ecosystem services that it provides afford it substantial
importance and reinforce the case for its protection and restoration. Successful local restoration activities
highlight the feasibility of regeneration of TDEF, even from severely degraded
and eroded land, and the associated regeneration of ecological and
socio-economic values.
Keywords: Coromandel Coast, ecosystem services,
restoration, Tamil Nadu, TDEF, tropical dry evergreen forest.
doi: http://doi.org/10.11609/jott.2807.10.6.11760-11769
Editor: Aparna Watve, Biome
Conservation Foundation, Pune, India. Date
of publication: 26 May 2018 (online & print)
Manuscript details: Ms
# 2807 | Received 12 January 2017 | Final received 25 April 2018 | Finally
accepted 01 May 2018
Citation: Everard, M. (2018). The characteristics, representativeness,
function and conservation importance of tropical dry evergreen forest on
Indias Coromandel Coast.
Journal of Threatened Taxa 10(6): 11760–11769; http://doi.org/10.11609/jott.2807.10.6.11760-11769
Copyright: Everard 2018. Creative Commons Attribution 4.0 International License. JoTT allows unrestricted use of this article in any medium,
reproduction and distribution by providing adequate credit to the authors and
the source of publication.
Funding: Lloyds Register Foundation;
RICS Research Trust; The Converging World; John Pontin Trust; Pitchandikulam Bio
Resources Centre.
Competing interests: The author declares no competing interests.
Author
Details: Dr. Mark Everards research interests include ecosystem services, in
particular human-ecosystem interdependences underpinning development
challenges. He works extensively in
India, with significant experience in other developing world settings including
elsewhere in South Asia and both East and South Africa. Mark is a communicator in scientific and
popular media about the multiple values that ecosystems provide for people.
Acknowledgements: The author is grateful for co-funding by Lloyds Register Foundation, a
charitable foundation helping to protect life and property by supporting
engineering-related education, public engagement and the application of
research. Also to the RICS Research
Trust, which made the senior authors travel possible. Thanks too for the support of The
Converging World, the John Pontin Trust and the Pitchandikulam Bio Resources Centre
Introduction
The
Coromandel Coast comprises the southeastern coastal
region of peninsular India seaward of the Eastern Ghats and bordering the Bay
of Bengal, between False Divi Point in the north and Kanyakumari (Indias southern tip). There is a long history of human
activity on the Coromandel Coast, ranging back to at least the second century
AD based on artefacts from a Roman port near Pondicherry (Begley 1993; Begley
et al. 1996) and possibly earlier with evidence of trade links with Egypt
mediated by Romans (Chandra 2011).
There is evidence of continuing occupation and settlement including
archaeological records of villages dating back to the Chola
period (around 1,000AD), settlements by European powers and a diversity of
trading activities from the first half of the 16th century, and
increasing Tamil populations in growing towns and villages. The population and, it can be assumed,
associated environmental pressures of Tamil Nadu have boomed over the past six
decades, rising from just over 30 million in 1951 to over 48 million in 1981
and continuing to ascend from nearly 79 million in 2014 (Indiaonline
undated). It can be assumed that
the native vegetation prior to its extensive exploitation, conversion or other
forms of management was a climatic climax community, and in all probability a
forest. Determining the precise
natural forest type of the Coromandel Coast, however, has been contentious due
as much to an extended history of landscape use and manipulation by dense
populations long before formal surveys had been undertaken as to high natural
climatic and topographical variability.
This
paper draws on literature concerning the native forest of the central area of
the Coromandel Coast, particularly the often polarised
views around the tropical dry evergreen forest (TDEF), to describe its
characteristics, representativeness, functions and conservation importance.
Coastal geography and development of the
regional flora
The
geological history of southern India includes migration of the Indian Plate, a
major tectonic plate split off from Gondwanaland, that began
moving northwards at about 15cm year-1 during the late Cretaceous
Period (about 90 million years ago) (Zhu et al. 2005). Its collision with the Eurasian
landmass, occurring from between 60 and 50 million years ago, is an ongoing process forming the Himalayan range and affecting
physical and biological geography at subcontinental
scale (Valdiya 2010). Data from fossil and contemporary fauna
indicate that, throughout the late Cretaceous, India maintained exchanges with
adjacent lands with no evidence, for example through a history of endemic
species, of an extended period of isolation before its contact with Eurasia
(Briggs 2003). The ecology of India
therefore reflects substantial changes in physical geography, climatic zones
and species invasions.
Southern
Indias biodiversity is diversified still further by wide variations in climate
and geography across the contemporary Deccan Peninsula. Deciduous forests are most common on the
better watered Malabar Coast and Western Ghats, the Western Ghats comprising a
globally significant biodiversity hotspot (Myers et al. 2000). Deccan thorn scrub forests are naturally
more widespread in the drier, interior Deccan plateau. The Coromandel Coast falls in the rain
shadow of the Western Ghats mountain range rendering the city of Chennai one of
the driest cities in the country due in part also to the unpredictable,
seasonal nature of the monsoon.
Annual rainfall on the Coromandel Coast is approximately 1,250mm, but
with a distinct gradation from north to south, and a highly seasonal pattern
including light rains from June to September with intermittent heavy falls
between October and December mainly resulting from depressions forming in the
Bay of Bengal (the northeastern monsoon) (Balasubramanian & Bole 1993; Blanchflower
2003).
The
Coromandel Coast is host to the East Deccan dry evergreen forests ecoregion, constituting a narrow coastal strip and covering
an area of 25,500km2.
Only two other ecoregions exhibit a similar
pattern, the Sri Lanka dry-zone dry evergreen forests and the southeastern Indochina dry evergreen forests, reflecting
related tectonic history and current climatic conditions (Dabholkar
1962). Similar forest assemblages
are also found in northeastern Thailand (Bunyavejchewin 1999).
The original vegetation of the ecoregion
comprised forests with an understory of evergreen trees and an emergent canopy
of taller deciduous trees, including Sal Shorea
robusta, Albizia
amara and Chloroxylon
spp. (Dabholkar 1962).
Tropical dry evergreen forest (TDEF)
Champion
& Seth (1968), with interests related primarily to forestry, identified six
categories of Indian forests. One
of these was tropical dry forests, in turn broken down into three distinct
subtypes: tropical dry deciduous forests, tropical thorn forests, and tropical
dry evergreen forests (TDEF). Under the Champion & Seth (1968) classification, typical TDEF
is dominated by the trees Manilkara hexandra, Memecylon
spp., Diospyros sp., Eugenia
spp., Chloroxylon sweitenia,
and Albizia amara,
though further sub-types were also noted. The definition of TDEF was therefore
broad and described as 9–12 m high forest growing in lateritic and sand
dune soils with a complete canopy and distributed along the coasts of Karnataka
and Tamil Nadu states, and the Nellore District of Andhra Pradesh State.
Dabholkar (1962) characterised TDEF as a climax constituted by Albizia amara - Acacia
leucophloea communities, recognising eight
successional stages in its development from original ecoregional
forests with an understory of evergreen trees and an emergent canopy of taller
deciduous trees. Dabholkar (1962) attributed the elimination of the
deciduous canopy species to intensive human forest use over a period of centuries. Meher-Homji
(1974) corroborated the derivation of TDEF from dry deciduous forest by the
disappearance of many typical deciduous species and invasion by some endemic
species of the drier eastern half of southern India. Meher-Homji
(1974) supported this analysis with an exhaustive list of TDEF species, with
notes on biogeographical and fossil origins, of which
the endemic southern Indian floristic element comprising >39% characteristic
TDEF species but <10% of companion and dry deciduous species. Hunneyball
(2003) found that 46-68% of tree species recorded across a range of TDEF sites
surveyed in the literature are evergreen in habit. Paul Blanchflower
(pers. comm. 30 March 2016) regards the evergreen nature of trees comprising
TDEF as an adaptation to intermittent and often unpredictable rains, species
with persistent, waxy leaves with low evapo-transpiration
rates offering a selective advantage to exploit unpredictable rainfall events
in preference to deciduous species that respond to more predictable annual
weather patterns.
WWF
(undated) recognises the vegetation in the eastern Deccan dry evergreen forests
(type IM0204) as being distinctive from most of the other dry forests,
occupying an area of 800 square miles (2,072km2) extending as a
narrow strip along the southern coastal areas of Andhra Pradesh and Tamil Nadu
classified as a Critical/Endangered habitat. The WWF vegetative definition of TDEF
rests on the analysis by Champion & Seth (1968), including observations
about the loss of original canopy-forming deciduous species, also noting a lack
of endemic mammals or birds though supporting 66 known mammal species (two of
them threatened) and 230 species of birds.
Meher-Homji (1974) found that only six tree
species were confined to dry evergreen forests: Manilkara
hexandra, Memecylon
umbellatum, Drypetes
sepiaria, Pterospermum
suberifolium, Carmona microphylla
(now Ehretia microphylla)
and Garcinia spicata. Whilst several of these species have a
wider global distribution beyond the Coromandel Coast ecoregion,
M. hexandra occurring as far north-east as
China and E. microphylla with an
Indo-Malaysian distribution, this is not inconsistent with the observation by Dabholkar (1962) that Coromandel Coast TDEF has
similarities with Sri Lanka dry-zone dry evergreen forests and southeastern Indochina dry evergreen forests reflecting
common tectonic history and current climatic conditions.
In a
study of 37 stands of TDEF, Blanchflower (2003) found
a total of 915 angiosperm species, both native and exotic, of which 343 were
woody species. Blanchflower
(2003) concluded that core tree species of remaining TDEF comprised: Albizia amara ssp. amara, A. lebbeck, Atalantia monophylla,
Azadirachta indica,
Cassia fistula, Chionanthus mala-elenga, Crateva
magna, Dalbergia lanceolaria,
Diospyros ebenum,
D. ferrea, Drypetes
sepiaria, Lannea
coromandelica, Lepisanthes
tetraphylla, Manikara
hexandra, Psydrax
dicoccos, Pterospermum
canescens, Sapindus
emarginata and Syzygium
cumini.
Blanchflower (2003) also concluded that broad
common characteristics of this apparent climax vegetation, reflecting
convergent evolution adapting to local climate, included evergreen, simple
leaves often with waxy upper surfaces, seeds often contained in small fruits
appearing between April and September, slow growth with wood generally dense
and hard, and generally lacking thorns though with some exceptions. Blanchflower
(2003) ascribed all of these features as resulting from convergent evolution
adapting to infrequent, intermittent and unpredictable rains. Given the current
fragmented and generally disturbed nature of TDEF patches, it is in practice
difficult to assert that this is a genuine climax community, but it is
certainly representative of an advanced stage in forest succession. Of the 310 woody species recorded at Pitchandikulam Forest (Pitchandikulam
Forest Virtual Herbarium: www.pitchandikulam-herbarium.org, accessed 25 October
2017), 55 are in the family Fabaceae suggesting an
additional nitrogen-fixing adaptation to low nutrient conditions.
Seeking
a consensus across these different characterisations of TDEF reveals as much
about the heterogeneity of extant forest stands as the commonalities. The commonly reported tree species
across studies (including those listed on the Pitchandikulam
Forest Virtual Herbarium) are Albizia amara (3 studies), Manilkara
hexandra (4 studies), Albizia
lebbeck (2 studies) Diospyros
ebenum or Diospyros
sp. (3 studies: the Pitchandikulam Forest
Virtual Herbarium lists six species of Diospyros)
and Drypetes sepiaria
(3 studies). Drawing from work by Meher-Homji (1974), Balachandran
et al. (2015) suggest that a classification of Albizia
amara community is a more useful definition
based on the wide distribution of the species across the coastal plain, and Sprangers & Balasubramanian
(1978) suggest Drypetes-Strychnos-Memecylon
association due to the occurrence of species dominance in this forest type.
What is
also clear from comparative analyses is the extent to which TDEF today is
highly fragmented and substantially degraded, and that this has been the case
for centuries. The original
characterisation of Champion & Seth (1968) noted that the few remaining
extant stands of TDEF were already substantially degraded through logging and
grazing. Although problems with
identifying original forest cover and type have been addressed previously, Ramanujam et al. (2003) estimate that 95% of the original forest cover has been cleared. Only about 4% to 5% of original TDEF
patches remain today (Meher-Homji 1992; Wikramanayake 2002).
Even in these isolated pockets, often afforded a degree of protection by
their close association with sacred groves surrounding temples (Ramanujam & Kadamban 2001),
species composition of the remaining forests has been altered by intensive
human use including the removal of taller trees (Ramanujam
et al. 2003). The size of sacred
groves, whilst variable, is also generally small ranging in size from clumps of
a few trees to a few hectares (Chandrakanth et al.
1990). The composition of surviving
stands of TDEF may therefore reflect pressures imposed upon them due to, as an
ecological generality, species often becoming hyper-disturbed in smaller
habitat fragments (Laurance 1997).
The
agency of human interference is not entirely damaging. The formation and characteristics of
TDEF cannot be dissociated from changing geographical, climatic, biogeographic
as well as human pressures, particularly the selective felling of taller
deciduous trees. These pressures
have changed over varying timescales, therefore constituting a habitat type in
flux, and also a cultural landscape the biodiversity and ecosystem
services of which are shaped by human management over an extended
history of settlement and land use (Antrop 1997,
2005; Jones-Walters 2008; Schaich et al. 2010). The ecoregions
remaining forests are now characterized by areas of leathery-leaved evergreen
forest, populated by a range of birds, mammals, reptiles, fungi and other taxa,
some of which play vital roles with associated close phenological
linkages in seed dispersal, pollination and other supporting services within
the forest ecosystem (Reddi & Reddi
1984; Balasubramanian & Bole 1993; Balasubramanian 1996; Blanchflower
2003).
Gadgil & Meher-Homji (1986), in a study identifying localities
significant for conservation of Indian biodiversity, developed an alternative
classification scheme that included a heterogeneous category of dry evergreen
forest spread over a wide range with a gradation of annual rainfall, suggesting
a categorisation of TDEF representative of a larger biome (as for example
tropical rainforest) rather than a specific vegetation type. This conclusion is supported by the
considerable variation between clumps of TDEF, even between forest patches in
close proximity to each other, as well as over time and in response to human
pressures as recorded by Hunneyball (2003) and Mani
& Parthasarathy (2009). This heterogeneity between patches may
be amplified by the fragmented nature of remnant TDEF, with greater
vulnerability to species exploitation, invasion and other external pressures.
This
story of TDEF development and characteristics is not without contest. In an opinion article, Daniels et al.
(2007) sought to dispel the myth of tropical dry evergreen forests of
India as the original vegetation type that covered the coasts of
peninsular India. Daniels et al.
(2007) question whether the assemblages of plants identified by Champion &
Seth (1968), Gadgil & Meher-Homji
(1986) and Meher-Homji (1974) as characterising TDEF
are remnants of a once widespread distinct forest type or are merely an
opportunistic assemblage of species adapted to local microclimatic conditions,
the most recent stage of succession rather than belonging to a climax
vegetation type. There is certainly
virtue in the argument erected by Daniels et al. (2007) as Meher-Homji
(1974), to whom the definitive definition of TDEF is often attributed, believed
that TDEF appears to derive from the dry deciduous forest through disappearance
of many typical deciduous species and invasion of some endemic species of the
drier eastern half of southern India.
It is therefore likely that TDEF is as much a now fragmented cultural
landscape as a formerly pervasive, uniform habitat type shaped solely by
fluctuating natural processes.
Current status of TDEF
On the southeastern seaboard of peninsular India, TDEF occurred
only within a very limited range, extending inland only between 30km (Gamble
1967) and 60km (Champion 1936).
This distribution is coincident with a high human population, the
long-term pressures of which have rendered TDEF one of the rarest
types of forest ecosystem found in the subcontinent (Blanchflower
2005). Consequently, TDEF has not
comprised a dense and extensive forest system in living memory, or perhaps even
recorded history. Rather, it has
existed as clumps of locally highly variable character in arid landscapes. For example, Venugopal
et al. (2008) summarised from the literature the areas and proportions of
different vegetative growth forms in TDEF stands, reproduced at Table 1. Data from Pitchandikulam
Forest (not listed by Venugopal et al. 2008) are
added to this Table 1.
Table 1. Areas and proportions of growth
forms recorded in the literature, after Venugopal et
al. (2008) with the additions of information from the Pitchandikulam
Forest
Site |
Area (ha) |
No. of species (GBH = girth
at breast height) |
Point Calimere |
2,400 |
200 dicots; 317 flowering plants (Blasco & Legris 1972; Balasubramanian & Bole 1993) |
Kuzhanthaikuppam |
1.2 |
54 (woody species 10cm GBH, sites combined) (Parthasarathy & Karthikayen
1997) |
Thirumanikuzhi |
1.6 |
54 (woody species 10cm GBH, sites combined) (Parthasarathy & Karthikayen
1997) |
Puthupet |
14 |
51 (woody species 10cm GBH) (Parthasarathy
& Sethi 1997) |
Arasadikuppam |
1.5 |
31 (woody species 10cm GBH) (Venkateswaran
& Parthasarathy 2003) |
Oorani |
1.8 |
30 (woody species 10cm GBH) (Venkateswaran
& Parthasarathy 2003) |
Pitchandikulam |
26.3 |
310 woody species of trees, climbers and shrubs of
which 55 are in the family Fabaceae (www.pitchandikulam-herbarium.org, accessed 5 April
2018) |
Long-term
human interventions are arguably one of the pressures that has characterised
TDEF. The Coromandel Coast ecoregion has been substantially altered by human activity
particularly throughout its long history, with an increasing intensity of
agriculture, forestry and urban development. Human pressures certainly influence
forest characteristics. Comparing
the vegetation in two TDEF stands on the Coromandel Coast, Visalakshi
(1995) concluded that soil properties and extent of human disturbance
constitute major factors influencing the vegetation in both forests. Venkateswaran
& Parthasarathy (2003) analysed human disturbance
in two stands of TDEF hosting sacred groves or temple forests, classifying site
disturbances into: site encroachment; temple visitor impacts; cattle and goat
browsing; and resource removal.
Comparison between the two sites found that greater disturbance reduced
forest stature, though it increased tree density albeit with more multi-stemmed
individual trees. The less disturbed
site also had a greater proportion (77%) of evergreen species compared to 65%
at the more disturbed site.
Comparison with other stands of TDEF further supported evidence that
human disturbances have impacts on forest stand characteristics such as stand
height, number of strata, tree density and basal area. Mani & Parthasarathy
(2009) investigated changes in tree species diversity, stand density and above
ground biomass in two TDEF forests after a 10-year interval (1995–2005),
recording 7.7% and 15% decreases in tree diversity, a 10.5% decrease and a
17.5% increase in tree density, and a 2.3% increase and a 6.8% decrease in
basal area, with additions and losses of species and considerable variation in
tree species, attributing most changes to the cumulative effects of site
quality and human activities. Baithalu et al. (2012, 2013) undertook similar re-censuses
of trees at two TDEF sites, recording species changes mainly attributed to
human interference. Most of the
Coromandel Coast ecoregions former forests have been
degraded into tropical dry evergreen scrublands, characterized by thorny
species such as Ziziphus glaberrima, Dichrostachys
cinerea, Catunaregam
spinosa, and Carissa spinarum
(Puri et al. 1989); however, even these agricultural
fallows, or wastelands (land not used for development), have societal value
as Kinhal & Parthasarathy
(2008) record that 64% of plant species found in them, mainly of widespread
distribution, serve a range of uses by local people. These uses are mainly for traditional
medicinal purposes (53 of 110 species), particularly by people lacking modern
medicine, with other uses including raft-making, hair
care, religious purposes, fuel wood, edible fruits, pesticide, fodder and
carpentry.
Less
than 1% of TDEF in the ecoregion lies in reserves or
protected areas, generally existing as small and fragmented stands (Rajan 2001).
Many extant TDEF stands are very small, such as the sacred grove near Marakkanam in Tamil Nadu preserving a section of evergreen
closed canopy forest and several other temple groves in the surrounding area
including Puthupet, Pillaichavadi,
Mudaliarchavadi, and Kottakarai
each preserving small enclaves of forest (Ramanujam
& Kadamban 2001). The Point Calimere
Wildlife and Bird Sanctuary protects a 17.26km2
enclave of dry evergreen forest (Rajan 2001 records
that it contains a 24km2 patch of TDEF comprising one of the largest
remnants of this forest type), as well as tidal wetlands and mangroves (Blasco & Legris 1973). Scattered remnant TDEF stands are found
in several other wildlife reserves in the region. Udayakumar
& Parthasarathy (2010) identified 75 TDEF sites
along the Coromandel Coast, many of them poorly known sites even within the
Indian subcontinent.
Human
interventions in TDEF also include active restoration. Restoration of indigenous TDEF at Pitchandikulam Forest, Tamil Nadu, has been in progress
since 1973 as a pioneering activity of the Auroville
green belt communities, transforming a 70-acre (28ha) bare eroded township site
into a complete ecosystem now comprising more than 800 species of plants (Pitchandikulam Forest, undated a). The Pitchandikulam
Bio Resource Centre (PBRC) continues to provide a focus for the teaching of
restoration ecology, environmental science, identification and use of
indigenous medicinal plants, and outreach with communities across the Kaliveli bioregion. PBRC is also working in close
partnership with local people to promote restoration of TDEF with an integrated
programme of educational, traditional medicinal and handicraft business and
female empowerment initiatives on 35 acres (0.14km2) of
reforestation at Nadukuppam to the north of Auroville near the Kaliveli
Estuary (Pitchandikulam Forest undated b). A floristic study of herbs and climbing
plants in a 160ha forest stand between the eastern shore of the fresh water Ousteri Lake and about 10km west of Puducherry
City, southern India, found that active human intervention over a 30-year
period, including introduction of plant species and interventions to enhance
soil fertility and groundwater levels, regenerated deteriorating TDEF
vegetation allowing recovery of 172 naturally occurring herbaceous, climbing
species with lowland herbaceous species also re-establishing as green cover at
ground level (Ponnuchamy et al. 2013).
The functional significance of TDEF
Whatever
the status of TDEF—definitive forest type or plastic biome distinctive to
the Coromandel Coast and some other regions with a similar
biogeography—the functions that it performs within the landscapes in
which it is found are significant.
The Millennium Ecosystem Assessment (2005) recorded a wealth of
ecosystem services provided by global forests, of which their role in climate
stabilisation through carbon storage and sequestration were particularly
significant. Everard
et al. (2017) explored the carbon sequestration services of restored TDEF,
concluding that they were highly significant and represented a powerful
business driver for forest restoration; however, it was also recognised that
climate regulation, whilst an anchor service (sensu
Everard 2014) providing the driving business
priority, is but one of a wide spectrum of interconnected ecosystem service
benefits stemming from both renewable energy generation and TDEF restoration as
summarised by Everard et al. (2017). A number of the (nonquantified)
ecosystem service benefits likely to arise from restored TDEF are reproduced in
Table 2.
All of
these values are significant for multiple constituencies of society, despite
historic tendencies to maximise one or a few generally utilitarian ecosystem
services in ecosystem use or management, driven by the generally narrow
disciplinary interests of specific government departments, regulatory bodies,
businesses, land managers or other constituencies often blind to or dismissive
of externalities. Recognition of
systemic outcomes across all ecosystem services and their associated
beneficiaries requires a more integrated basis for decision-making. Decisions about outcomes from management
therefore need to be addressed on a systemic basis, taking account of the
breadth of value systems and distributional outcomes central to the UN
Millennium Ecosystem Assessment categorisation of ecosystem services
(Millennium Ecosystem Assessment 2005), which took account of a broad range of
often nonsubstitutable economic and noneconomic
values flowing to humanity from nature.
Externalities entailed in contemporary intensive farming systems and
indeed the cumulative effects of agricultural activities are recognised as amongst
the greatest threats to wetland and other terrestrial ecosystems and their
broad range of services (Millennium Ecosystem Assessment 2005a,b). This consideration applies
as much to novel markets and service-enhancing schemes, however, which are not immune
from a blinkered approach to maximising a few favoured ecosystem services, to
the net detriment of non-focal services.
The hydrological roles of TDEF are particularly under-researched, though
forests are known to play important roles in the capture, retention and cycling
of water in landscapes (Shvidenko et al. 2005)
amongst a wide range of other ecosystem services, suggesting that restoration
of TDEF may have ecologically and socio-economically important roles to play in
reversing saline intrusion and other forms of groundwater and water resource
depletion on the Coromandel Coast (Bhattacharya et al. 2005).
Recognition
of the broader, primarily nonmarketed
services produced by ecosystems has been inconsistent. Some that are valued financially for recreation
and tourism have been more widely recognised (Sen et
al. 2014), whilst other habitats of widely-acknowledged spiritual and/or
heritage value also receive explicit protection including, for example,
informal taboos surrounding Hindu temples and more formal designations such as
qualifying features within world heritage sites and biosphere reserves. Diverse meanings attributed by different
stakeholder groups, however, are often poorly represented in decision-making,
with immediate utilitarian values often dominating perceptions and ensuing
decisions. Where ecosystem services
relating to traditional values are overlooked or undervalued, degradation of
ecosystems through narrow utilitarian uses undermines the physical health and
socio-economic wellbeing of communities, their cultural identity and their
long-term viability. Recognition
that human inhabitants shape the biodiversity and associated ecosystem services
of the cultural landscapes they inhabit is significant for informed and
integrated management (Antrop 1997, 2005;
Jones-Walters 2008). The diversity
of ecosystem services that these landscapes provide create strong ties between
humans and their natural surroundings, constituting amongst the strongest
incentives for people to engage with environmental conservation even if they
remain today too frequently marginalised relative to more quantitatively
assessed services (Schaich et al. 2010).
Table 2. Ecosystem service benefits
likely to arise from TDEF restoration (after Everard
2017)
Provisioning Services: Fresh water availability enhanced by quality, quantity and recycling processes. Enhanced aquifer recharge resulting from water retention and percolation. Food security and food availability by direct cropping or polyculture. Fuel and fibre resources available for use or trade. Genetic resources with potential value for stock or crops. Species with medicinal properties particularly used in traditional
medicine (Rajendran & Agarwal
2007; Parthasarathy et al. 2008). |
Regulating Services: Enhancement of air quality metabolism of pollutants, settlement of
particulate matter and avoidance of aeolian
erosion. Microclimate regulation within and adjacent to the forest. Global climate regulation, primarily by sequestering carbon. Catchment hydrology buffered by tree cover. Buffering natural hazards such as storms, protecting infrastructure and crops. Regulation of pests and diseases through predation and purification. Erosion regulation binding the surface of formerly eroded. Water purification through slowing water flows and purification processes. Pollination, by playing host to pollinating organisms. Regulation of soil salinisation through restoration of landscape
hydrology. Visual and noise buffering. |
Cultural Services: Cultural heritage traditionally associated with forests, including trees of particular
cultural significance such as the Banyan Ficus
benghalensis which is the national tree of the Republic of India. Recreational and tourism associated with forests. Aesthetic importance contributing to physical and psychological health. Spiritual importance including regenerating sacred groves and specimen trees (including
for example Peepal Ficus
religiosa and Banyan Ficus
benghalensis). Inspiration
of artistic, mythological, folklore and other cultural expressions. Income, employment and training opportunities, particularly women. Educational and research opportunities, both formal and informal. |
Supporting Services: Enhancement
of linked soil formation, primary production, nutrient
cycling, water recycling, photosynthetic oxygen production,
and provision of habitat rebuilding ecosystem integrity, functioning
and capacity to produce other beneficial services, particularly where it
replaces degraded habitats. |
Discussion
Some
classification schemes have definitive boundaries, for example discrete year
classes within populations of trees, fishes and other species with distinct
annual breeding seasons. Other
classification systems have more porous boundaries based on generic and often
descriptive clustering across a continuum for management or other purposes, as
for example chemical and biological river quality classes, human school years,
and distinctions between subspecies across a broad biogeographical
range.
The
initial segregation of Indias diverse forests into types and sub-types by
Champion & Seth (1968) was of the latter kind, splitting the diversity of
the whole of Indias forest cover into six categories each with sub-categories,
of which TDEF was one of three distinct subtypes within the tropical dry
forests category. Subsequent
analyses and characterisations of TDEF have encountered high variability within
and between often adjacent stands, as well as the significant degree to which
this forest type is shaped by both natural (such as soil, topography, climate
and genetic exchange with nearby habitats) and human agencies, significantly
including the selective removal of taller tropical dry deciduous tree species
to leave an evergreen canopy typically around 9m high. The heterogeneity of TDEF is further compounded
by its current fragmented state, the few remnant stands representing 4-5% of
original TDEF patches (Meher-Homji 1992; Wikramanayake 2002) and probably a great deal less today
due to increasing pressures from expanding human numbers as well as changing
lifestyles in Tamil Nadu.
Increasing fragmentation is likely to reduce the viability of some
native species, accelerate invasions from adjacent habitats and land uses, and increase vulnerability to grazing, timber and
fuelwood cropping and other human pressures.
TDEF
then is far from a definitive forest type, but is rather one that is variable
in characteristics. It is as much a
product of natural forces as reflective of cultural landscapes shaped by
long-term human interventions that may be formative, destructive and also
protective, as in the instances of temple and other sacred groves as well as
nature reserves. From both
biogeographic and cultural perspectives then, the wider evidence supports the
conclusion arrived at by Gadgil & Meher-Homji (1986) that a categorisation of TDEF represents
a generic biome rather than an unambiguously bounded vegetation type.
Recognition
of TDEF as a necessarily plastic biome, however, in no way undermines the value
of the categorisation. The
vegetation of the Coromandel Coast has undergone substantial conversion, with
loss of forests a significant feature over many centuries of intensifying human
history. It may not therefore be
possible to say with certainty which tree communities constitute a definitive
natural land cover, if indeed a meaningful baseline can be identified with
confidence given continuing tectonic, climatic and human fluxes overextended
time scales, as variations in exact forest composition can be expected across
rainfall, topography, soil type and other gradients and exchanges with adjacent
habitats. We understand some of the
species diversity found in fragmented remnant of this forest type, which can
form the basis for forest restoration efforts; however, local selection
pressures will be likely to influence eventual species dominance on a site- and
context-specific basis.
Nevertheless, whatever the final species composition, restoration of
this broad forest type/biome is a priority if the carrying capacity of
ecosystem services generated across the Coromandel Coast—for wildlife, hydrology,
soil fertility and a range of associated human needs—is to be regenerated
as a major contribution to sustainable development.
The 40+
year history of regeneration at Pitchandikulam
Forest, reflective of significant and enduring dedicated efforts from a
baseline of severely degraded and eroded land and now manifesting as a mature
forest community with a wide assemblage of recovered species across multiple
taxa, highlights that when an appropriate mix of species is planted and
nurtured then a regionally representative forest can re-emerge from what was
once a virtually useless and uninhabitable wasteland. As noted previously, whilst the Pitchandikulam Forest is largely protected, disturbed only
by largely non-disruptive educational and research uses, it is contentious to
assert that it represents a genuine climax community though it is certainly
representative of an advanced stage in forest succession. There are also other localised patches
of TDEF being restored in the Coromandel Coast strip, including at the Auroville Botanic Gardens and also at Nadukuppam
in the Kaliveli catchment, where successes achieved
at Pitchandikulum are being replicated with the
involvement of people from local villages.
Beyond
the biological relevance and demonstration of the potential for regeneration of
a regionally representative biome, if not an exact replica of what may have
preceded the previous history of forest and landscape destruction, there are
also significant functional reasons for recognising, valuing and regenerating
TDEF. Though derived on a largely
illustrative basis, the analyses of ecosystem services likely to be enhanced by
restoration of TDEF includes significant calculated benefits stemming from the
anchor service of climate regulation, but also a wider range of connected
enhancements to additional ecosystem services likely (albeit not quantified) to
stem from regenerated forest. The
role of restoration of TDEF in recovery of the damaged freshwater systems of
the Coromandel Coast may be particularly significant. Recognition of all of these diverse
benefits, not merely those closest to markets, is important for connecting with
the value systems of local people, as for example those instrumental in
safeguarding remnant sacred groves, potentially representing strong incentives
for their engagement in conservation efforts (Schaich
et al. 2010). This emphasises the
importance and indeed dependence of ecosystem regeneration on benefits
connecting with the real-life experiences of local people, their roles as
active managers, the importance to them of less tangible spiritual and cultural
values, and collaboration across scales (Folke et al.
2005). Taking account of cultural
context and associated, often highly localised cultural values is vital in
decision-making that represents the needs and perspectives, and elicits the
support, of local people who are at the root of community-based solutions. Local-scale decision-making and resource
stewardship can make significant differences at landscape scale, rebuilding
support, management action and ensuing ecosystem resilience from village to
sub-catchment and up to progressively higher scales.
In
conclusion, TDEF is at best a coarse classification of a regionally
representative forest type, plastic in local form due to a range of natural and
human factors and significantly influenced by local variability in both as well
as edge effects. It may well
represent a biome rather than a definitive vegetative type, but the
classification nevertheless remains valid if viewed from a functional
perspective rather than a purist botanical definition. If understood in this context, the term
TDEF remains useful, and indeed has already done so as evidenced by restoration
efforts. The term Coromandel Coast
forest, however, may be less contentious, and therefore more helpful, if it
evades some of the criticism levelled at TDEF as a strict botanical rather than
a more general descriptor.
What is
of overriding importance, and a matter of generally unspoken consensus of
supporters and critics of the term TDEF alike, is that more of it is needed to
rebuild severely degraded regional ecology, ecosystem functioning and with it a
diversity of ecosystem services helpful in addressing a range of local problems
including, as pressing examples, combating coastal saline groundwater intrusion
and the erosion of soil quality and quantity, hydrological buffering rebuilding
resilience to droughts and flooding, and pollination of crops in a
predominantly agricultural region underpinning food and livelihood security.
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