The benefits of fringing mangrove systems to Mumbai

Abstract

Mumbai's mangroves have been significantly depleted through historical city development and continuing encroachment. These mangroves are important for production of a range of ecosystem services.
Recent conservation‐oriented orders in India's courts of justice recognize some of the values associated with mangroves, though wider benefits flow to diverse stakeholders through many additional ecosystem services provided by Mumbai's remaining fringe of mangrove systems.
Valuation of ecosystem services on a semi‐quantitative basis and, where possible, using value‐transfer techniques from other relevant studies, demonstrates in indicative terms the magnitude of the benefits provided to Mumbai by its mangrove systems and connected habitats. Values could only be deduced approximately as most services lie outside the current market.
Conservative valuation and assumptions about cumulative, non‐quantified value emphasize the importance of mangroves to the built environment, people, and future security of Mumbai. This reinforces the need for conservation and restoration of the mangrove resource, particularly as a matter of ‘natural insurance’ in the light of a changing climate, sea‐level rise and other emerging sustainability challenges.
Current mangrove extent is at its most sparse on the seaward border of the city, arguably where greatest protection is required from storms, tsunamis, and other threats.
Investment in mangrove restoration would add significant value to the city region. Novel economic tools such as ‘payments for ecosystem services’ (PES) may be used to protect or enhance the mangrove stands of Mumbai.
Copyright © 2014 John Wiley & Sons, Ltd.

Full text

CASE STUDIES AND REVIEWS
The benefits of fringing mangrove systems to Mumbai
MARK EVERARD
a,
*, ROHIT RS JHA
b
and SHAUN RUSSELL
c
a
Faculty of Environment and Technology, University of the West of England (UWE), Bristol, UK
b
Post-Graduate Program in Wildlife Biology and Conservation, WCS-India Program, National Centre for
Biological Sciences, Bengaluru, India
c
Wales Environment Research Hub, Environment Centre Wales, Bangor, Gwynedd, UK
ABSTRACT
1. Mumbai’s mangroves have been significantly depleted through historical city development and continuing
encroachment. These mangroves are important for production of a range of ecosystem services.
2. Recent conservation-oriented orders in India’s courts of justice recognize some of the values associated with
mangroves, though wider benefits flow to diverse stakeholders through many additional ecosystem services
provided by Mumbai’s remaining fringe of mangrove systems.
3. Valuation of ecosystem services on a semi-quantitative basis and, where possible, using value-transfer
techniques from other relevant studies, demonstrates in indicative terms the magnitude of the benefits provided
to Mumbai by its mangrove systems and connected habitats. Values could only be deduced approximately as most
services lie outside the current market.
4. Conservative valuation and assumptions about cumulative, non-quantified value emphasize the importance
of mangroves to the built environment, people, and future security of Mumbai. This reinforces the need for
conservation and restoration of the mangrove resource, particularly as a matter of ‘natural insurance’in the light
of a changing climate, sea-level rise and other emerging sustainability challenges.
5. Current mangrove extent is at its most sparse on the seaward border of the city, arguably where greatest
protection is required from storms, tsunamis, and other threats.
6. Investment in mangrove restoration would add significant value to the city region. Novel economic tools such
as ‘payments for ecosystem services’(PES) may be used to protect or enhance the mangrove stands of Mumbai.
Copyright #2014 John Wiley & Sons, Ltd.
Received 27 August 2013; Revised 26 October 2013; Accepted 19 November 2013
KEY WORDS: mangroves; Mumbai; ecosystem services; benefits; conservation; regulation; economics
INTRODUCTION
Mumbai is one of the world’s mega-cities with a
population in excess of 20 million (including
suburbs). It is also low-lying, much of it built on
‘reclaimed’land including former mangroves
intersecting what was previously seven islands.
Encroachment into the remaining mangroves was
commonplace until a Coastal Regulation Zone
*Correspondence to: Mark Everard, Faculty of Environment and Technology, University of the West of England (UWE), Bristol, UK. E-mail:
mark@pundamilia.co.uk
Copyright #2014 John Wiley & Sons, Ltd.
AQUATIC CONSERVATION: MARINE AND FRESHWATER ECOSYSTEMS
Aquatic Conserv: Mar. Freshw. Ecosyst. 24: 256–274 (2014)
Published online 8 January 2014 in Wiley Online Library
(wileyonlinelibrary.com). DOI: 10.1002/aqc.2433

(CRZ) was notified across India, initially in 1991 but
substantially reinforced in 2011 to impose restrictions
on industries and a range of other potentially harmful
activities (Ministry of Environment and Forests,
2011). This all-India CRZ was established in order
to ensure livelihood security for fisher communities
and other local communities living in the coastal
areas, the conservation and protection of unique
coastal and marine areas, and to promote
sustainable forms of development. An additional
Bombay High Court order banning construction
activities within 50 m of remaining mangroves
regardless of land ownership specifically in Mumbai
city has arrested significantly the tendency to exploit
the remaining mangrove resource, and this has been
extensively amended to address writs complaining of
continued abuse of mangroves (High Court of
Judicature at Bombay, 2006). As much of Greater
Mumbai is situated close to sea level, the role of
mangroves is seen as significant in mitigating
vulnerability to storm surges. As Mumbai has some of
the highest real estate land values in the world,
1
the
potential for damage is substantial. This highlights the
importance of natural storm buffering services,
although degradation of additional ecosystem services
may also be significant where mangroves are lost to
encroachment or other human activities.
The study reported in this paper draws upon
available evidence to make an initial assessment
of the multiple societal values stemming from
ecosystem services provided by Mumbai’s mangrove
systems. It achieves this by reinterpreting available
information around the ecosystem services
framework then applying value transfer and a
range of other techniques developed in the UK
(summarized by Everard (2012) and formulated into
guidance by Everard and Waters (2013)) to evaluate
the multiple benefits that Mumbai’s mangrove
systems provide for the city and its residents.
The purpose of the study is to articulate in
indicative terms the range and magnitude of
benefits provided by mangrove systems, leading to
recommendations for further research and also for
the sustainable management of the mangrove
resource based on clearly articulated benefits for
Mumbai. This in turn is intended to support
exploration by the State of Maharashtra of the
benefits of conducting an ecosystem assessment study
akin to the UK National Ecosystem Assessment
(UKNEA) (Times of India, 2012a), and additional
interests in designating some of the mangroves in the
Mumbai region under the international Ramsar
Convention (Times of India, 2012b).
ASSESSING THE ECOSYSTEM SERVICE
BENEFITS OF THE MANGROVES OF THE
MUMBAI REGION
Recognition of multiple values associated with
mangrove systems
Voa et al. (2012) reviewed the ecosystem services
provided by mangrove systems, determining
substantial cumulative value across a broad swathe
of services, notably including protection from
natural hazards such as storm surges and tsunamis.
Indeed, Danielsen etal.(2005)found‘markedly less’
damage to areas inland from the coast shielded
from the impacts of the 2004 Indian Ocean
Tsunami by coastal tree vegetation. This was
among the most devastating natural disasters in
recent history killing 229 866 people and causing
billions of US$ in damage (United Nations, 2007),
with mangroves constituting the most important
protective coastal tree vegetation in the area.
Villages in and around Bhitarkanika National Park
in the Indian state of Orissa were considered to have
been spared from much of the damage caused by a
1999 super cyclone primarily due to the presence of
extensive tracts of mangrove forest (Ramachandran
et al., 2005; Das and Vincent, 2009). A review of
tsunami impacts by Forbes and Broadhead (2007)
suggested that coastal forests, particularly
mangroves but with the exception of ‘altered
forests’, mitigated the effects of the tsunami, which
justifies both tree planting programmes and the
establishment and protection of coastal buffer zones
in tsunami-affected countries. These protective
functions have been observed in India (Badola and
Hussain, 2005; Chadha et al., 2005; Ramanamurthy
1
An example of this is the acquisition of prime development land in
Mumbai in May 2010 by the Lodha Group, one of India’s premier
real estate developers dealing in residential and commercial
properties, totalling 81 818 INR m
–2
for land (Business Standard,
2010). (81.8 million INR ha
–1
equates approximately to $US 1.56
million or £0.96 million at April 2012 exchange rates).
THE BENEFITS OF FRINGING MANGROVE SYSTEMS TO MUMBAI 257
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et al., 2005). Other coastal habitats such as sand
dunes are also known to serve important roles in
defence from natural hazards including storm
surges and coastal flooding among a range of other
services (Everard et al., 2010).
In addition to protection from natural hazards
(Barbier, 2006; Chang et al., 2006), a wide variety
of ecosystem service values are attributed
to mangrove systems, including serving an
important role in enhancing fisheries (Mumby
et al., 2004), both directly and through acting as
nursery areas (Warren-Rhodes etal., 2011). Benefits
realized directly from mangroves in three Solomon
Islands villages include a strong reliance on various
mangrove goods for subsistence and cash,
particularly firewood, food and building materials,
with widespread local recognition of the value of
mangroves for fish and nursery habitat and storm
protection (Warren-Rhodes et al., 2011).
In a meta-analysis of mangroves in south-east
Asia, Brander et al. (2012) determined mean and
median values of 4185 and 239 US$ ha
–1
yr
–1
respectively (2007 prices), reflecting a range of
services that varied across study sites due to
characteristics such as the nature of the biophysical
site and socio-economic context of beneficiaries.
Barbier (2007) concluded that the economic annual
value of just 1ha of mangrove forest, determined by
adding values deduced for collected wood and non-
wood forest products, fishery, nursery, and coastal
protection against storms, was $12 392. The value
proposed by Barbier (2007) substantially exceeds
those suggested by Brander etal. (2012), perhaps
related to differences in the range of services
assessed, but certainly introducing uncertainty into
how most reliably to value mangrove systems. The
purpose of the study is to articulate the range and
magnitude of benefits provided by mangrove systems
using available information reinterpreted around the
ecosystem services framework, leading to
recommendations for their sustainable management
based on clearly articulated benefits for Mumbai and
more universally for mangrove systems.
Mangrove loss
Notwithstanding the importance of mangrove
systems and their services, mangroves are one of
the world’s most threatened tropical ecosystem
types (Valiela et al., 2001; Warren-Rhodes et al.,
2011; Siikamäki et al., 2012). The Millennium
Ecosystem Assessment (2005) found that nearly a
quarter of global mangrove forests have been lost
since about 1980, along with their capacity to
buffer coastlines from storms.
This is significant as Montoya and Raffaelli (2010)
observe that climate change is affecting, and will
affect, biotic interactions and the provision of
ecosystem services at largely unknown pace and
magnitude, and that the provision of services would
be mostly compromised in already degraded systems.
In the light of the important functions provided by
mangroves, the implications for damage to life,
livelihoods, and infrastructure are severe. This
creates a clear incentive for the protection, and
ideally rehabilitation, of mangrove systems.
The mangroves of India including Mumbai
Within India, recognition of at least some of these
values had led to a landmark ban in 2005 by the
Bombay High Court to stop the destruction of
mangrove forests, shortly after the 2004 Indian
Ocean Tsunami that struck the eastern Indian
coast. Although this tsunami badly affected many
parts of Indonesia and Sri Lanka, it was
recognized that areas with healthy mangrove
forests and coral reefs had stronger resistance to
the wave’s power and also recovered faster
(Vijayaraghavan, 2011).
The mangroves around Mumbai were reported as
having an aerial extent of some 37 km
2
(3700 ha) in
the early 1990s but that Mumbai has probably lost
40% of its mangroves in the preceding decade,
largely because of reclamation for housing, slums,
sewage treatment and garbage dumps (Chavan
et al., 2011, drawing information from http://www.
mangroves.godrej.com/MangrovesinMumbai.htm).
This implies a current aerial extent of 22.2 km
2
(2220 ha). However, Table 1 provides survey data
published by Vijay et al. (2005) suggesting 56.4 km
2
(5640 ha) of extant mangroves including both
‘dense’and ‘sparse’stands. Time series data
reproduced from Vijay et al.(2005)inTable1
substantiates perceptions about a sharp decline of
mangrove extent throughout the last decade of the
M. EVERARD ET AL.258
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20th century, through the rapid decline in area of
‘sparse mangrove’yet net increase in area of ‘dense
mangroves’suggests some greater complexity
underlying the overall trend. By contrast, the
Mangrove Action Project (2008) records an aerial
extent of 60 km
2
of mangroves in Mumbai and
its neighbouring areas, of which more than
5800 hectares (58 km
2
)wasprotectedforests
(Vijayaraghavan, 2011). Recent satellite data
indicates that Mumbai and its adjoining areas have,
at present, 61.7 km
2
(6170 ha) of mangroves,
including those on private lands (Times of India,
2012c), with 5800 ha already notified as ’Protected
Forests’under the landmark Bombay High Court
order of 2005 (High Court of Judicature at
Bombay, 2006). Subsequently, in June 2013, the
Maharashtra state government passed a resolution
to declare Mumbai’s mangrove forests on
government land as ‘Reserved forests’(Down to
Earth, 2013) under section 4 of the Indian
Forest Act, 1927. Under this legislation, ‘Reserved
forest’status mandates a higher level of protection
(all human activities are disallowed except for
those that are explicitly permitted) compared to
‘Protected Forests’(under which all activities are
permitted except those that are specifically
disallowed), though final notification can only be
declared after all rights have been settled by a
claimant officer. Although this designation excludes
mangroves on private lands, the declaration of
mangroves as ‘Reserved forests’prevents any
new rights claims over the land. The raising of legal
status therefore provides a mechanism to effect
improved protection of the 277 hectares in the
island city and 3720 hectares in the suburbs, with
this level of protection being put in place for
1471 hectares in Navi Mumbai and 8862 hectares
in the Raigad District of Maharashtra. Excluding
mangrove coverage in Raigad, much of which
lies southwards along the coast, this totals
5468 ha (55 km
2
)of‘Reserved’mangroves in the
Greater Mumbai area (reported in Times of India,
2013). Figure 1, derived from Vijay et al. (2005),
illustrates this aerial extent of mangroves around
Mumbai. Reported estimates range from 2220 ha to
6170 ha (2.2 km
2
to 6.2 km
2
). Seeking a more
reliable estimate of mangrove coverage from
Google Earth or other remote sensing data will not
necessarily increase certainty due, for example, to
different densities and conditions of mangrove and
their tendency to change in extent under the
opposing forces of encroachment and conservation.
Therefore, the intermediate area of 56.4 km
2
(5640 ha) extant mangroves reported by Vijay et al.
(2005), broadly consistent with the Government of
India figure of 5468 ha of ‘Reserved’mangroves, is
used as a conservative basis for the extent of
mangroves in the Greater Mumbai area in further
analyses in this paper.
ECOSYSTEM SERVICE ASSESSMENT
METHODS
Assessment and, where possible, valuation of
ecosystem services is a tool for indicative comparison
of land use change. It does not automatically imply
that there is a willingness to pay for quantified
services, nor that there are readily exploitable
markets for them. However, the purpose of
Table 1. Area under mangrove in Mumbai (from Vijay et al., 2005)
Year
Mangrove classes (km
2
)
Total area (km
2
)Sparse mangroves Dense mangroves
1990 75.08 (80.78%) 17.86 (19.22%) 92.94 (100%)
1996 43.44 (64.92%) 23.47 (35.08%) 66.91 (100%)
2001 30.80 (54.61%) 25.60 (45.39%) 56.40 (100%)
10 km
Urban area
Extant mangroves
Coastline
N
Figure 1. Distribution of mangroves around Mumbai (redrawn from
Vijay et al., 2005).
THE BENEFITS OF FRINGING MANGROVE SYSTEMS TO MUMBAI 259
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assessment is to reveal values that may have been
formerly overlooked such that they can lead to
better-informed and more equitable, sustainable
decisions of greater cumulative value to all in society.
Using the ecosystem services classification
scheme of the Millennium Ecosystem Assessment
(2005), existing information was reinterpreted to
explore the range and magnitude of societal
benefits likely to derive from the mangrove
systems around Mumbai. Where possible, indicative
values were transferred conservatively from related
studies or deduced by other techniques developed
(summarized by Everard (2012) from a review of
ecosystem services valuation studies and formulated
into guidance by Everard and Waters (2013)) to
evaluate the multiple benefits that Mumbai’s
mangrove systems provide for the city and its
residents. Value transfer methods estimate the
value of services and goods provided by an
ecosystem through applying conservative and stated
assumptions when ‘transferring’values deduced in
relevant pre-existing valuation studies of ‘what are
known as ‘policy sites’. These pre-existing studies
may comprise unit value transfer, based on discrete
policy sites, or else meta-analytic function transfer,
using a value function estimated from a collection
of studies. The main advantage of benefits transfer
is avoidance of resource-intensive primary valuation
studies. However, the robustness of value transfer
depends on the availability of suitable pre-existing
studies, success of the ‘matching’of the policy site
to an appropriate prior study site, appropriate and
conservative assumptions used to adjust valuation
between studies, and the quality of the original
economic valuation study and its relevance to the
present day (eftec, 2010).
The Barbier (2007) and Brander et al. (2012) studies
cited previously could be used for meta-analytic
function transfer. Simplistic multiplication of the
area extent of Mumbai’s mangroves (5640 ha) by
per-hectare meta-data for net annual service benefits
yields of US$23.6 million (based on the Brander
et al. (2012) mean value), US$1.3 million (based on
the Brander et al. (2012) median value) and US$69.9
million (derived from the Barbier (2007) estimate).
Bespoke pre-existing site-specific valuation studies
for tropical mangrove systems are sparse. Although
a study by Emerton and Kekulandala (2003)
which estimated Sri Lankan Rupee values for
Muthurajawela Marsh in Sri Lanka encompasses a
range of habitats of which mangroves comprise a
relatively small proportion, net values from this
study are considered appropriate for the indicative
purposes of the present study of the benefits provided
by Mumbai’s mangrove systems as Muthurajawela
Marsh is of not dissimilar extent (3068 ha) and offers
services close to the urban centres of Colombo and
Negombo. Values transferred from Muthurajawela
Marsh were multiplied by a currency conversion rate
of 0.393 (INR, or Indian Rupees, per SRR, or Sri
Lankan Rupees, as of March 2012) and also a factor
of 1.84 for area difference (5640 ha extant mangroves
in Mumbai versus the 3068 ha of Muthurajawela
Marsh), yielding a compound adjustment factor
of 0.72 to determine indicative transferred
values. Notwithstanding application of conservative
assumptions, there is clearly significant uncertainty
associated with values deduced for Mumbai’s
mangroves because of uncertainties in the original
study as well as context-specific differences between
the two locations. No attempt was made to correct
forpresent-dayvaluesassuchacorrectionwas
believed to lie well within the overall error
introduced by these other factors, and may have
given a false sense of certainty about the indicative
values derived. However, the paucity of more
relevant studies highlights a significant research gap.
It was not possible to ascribe values for most
services, as indeed for a number of other services for
which monetary values could be determined for
some aspects. Therefore, in all cases, ‘likelihood of
impact’semi-quantitative scores published by the
UK Government’s Department for Environment,
Food and Rural Affairs (Defra, 2007) were
determined by the expert judgement of the authors
with additional input from two British scientists
(Tim Pagella and Charlie Falzon) and one Indian
NGO Director (Shivaji Chavan) collaborating
on ecosystem assessment in Mumbai. Where
full quantification was not possible, these
semi-quantitative scores were used to support the
valuation study. The Defra scoring system recognizes
the following likelihoods of impact:
‘++’Significantly positive
‘+’Positive
M. EVERARD ET AL.260
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‘0’Neutral
‘-‘Negative
‘--‘Significantly negative
‘?’Unknown or contentious
RESULTS
On the basis of the above information about
mangrove extent and distribution and from the
wider literature, a range of information sources
were collated with a view to determining
the ecosystem services provided by Mumbai’s
mangroves, their likely value and, where possible,
some more detailed valuation. These analyses
are recorded in Tables 2, 3, 4 and 5 for
provisioning, regulatory, cultural, and supporting
services, respectively.
As noted in the analysis of the provisioning service
of ‘fibre and fuel’(Table 2), direct harvesting of
mangroves is not only dissuaded but is now also
illegal, and extraction might also conflict with the
provision of other mangrove-derived services. For
these reasons, the deduced economic value of the
service of ‘fibre and fuel’isnotusedtoassessoverall
cumulative service supply in the following calculations.
The six other services for which it was possible to
transfer indicative economic values (fresh water @
2.72 million INR yr
–1
, food @ 40.58 million INR yr
–1
,
carbon sequestration @ 0.56 million INR yr
–1
,
flood control @ 348.40 million INR yr
–1
,industrial
and domestic wastewater treatment value @ 119.57
million INR yr
–1
, and recreation @ 3.79 million INR
yr
–1
) yield a total annual value of 515.62 million
INR yr
–1
(US$ 7.73 million yr
–1
at an August 2013
conversion ratio). There is of course significant
uncertainty associated with these transferred values,
which should be regarded as merely indicative rather
than having any absolute meaning. The unevenness
of confidence in the valuation of different services
and uncertainties in values transferred means that
ascribing robust values to all services on a
comparative basis is not yet possible.
Beyond the narrow subset of valued services, 10
other non-monetized services were assessed as
‘significantly positive’, notably including the service
of hazard/storm regulation (for example regulation
of the impacts of extreme events such as tsunamis
and storms) which is likely to be disproportionately
high given the low-lying profile of the city and its
infrastructure and high real estate values.
Furthermore, some services are assessed only
partially albeit assessed as likely to be ‘significantly
positive’. An example here is the regulatory service
of ‘climate regulation’(Table 3) for which an
indicative monetary value is transferred for carbon
sequestration, though none could be derived for
production of methane or nitrous oxide, or for the
likely substantial losses of stored carbon on
mangrove conversion for which the literature is
equivocal. Neither was it possible to value regulation
of local microclimate including the breakdown of
‘heat islands’,whichmaybeasignificant,aswellas
asignificantly overlooked service particularly in such
a dense mega-city as Mumbai.
Another set of benefits considered likely to be
‘significantly positive’on the basis of health
and lifestyle benefits were cultural service benefits
(Table 4) associated with accessible mangrove-edge
recreation including, jogging, walking, and other
informal activities that were observed to be
extensively exploited. The contribution of mangroves
to food production is also acknowledged as
under-representing the cumulatively important yet
unquantified importance of small-scale subsistence
and commercial fisheries often associated with
mangrove systems.
None of the nine services assessed as likely to be
‘positive’were monetized.
DISCUSSION
The value of Mumbai’s mangrove systems
Many of the pressures contributing to current
sustainability challenges stem from omission of the
benefits provided by whole ecosystems from
decision-making, favouring often detrimental
ecosystem exploitation to maximize a few services
captured by the market. Given significant gaps in
capacity to value many of the services provided by
mangrove systems with any degree of confidence,
using just the approximately monetized values and
overlooking other non-quantified services, would
risk perpetuating the mistakes of the past.
This is particularly the case given the likelihood,
following the considerations above, that the
THE BENEFITS OF FRINGING MANGROVE SYSTEMS TO MUMBAI 261
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Table 2. Provisioning services provided by Mumbai’s mangroves
Provisioning services
Ecosystem service Likely significance Description of service and, where possible, indicative value
Fresh water ++ Mangroves act as natural filtration systems, capable of absorbing and/or
metabolizing pollutants such as heavy metals and other toxic substances as well
as nutrients and suspended matter including sewage (ZSL). The extent to which
these purification processes contribute to the final provisioning service of fresh
water production for the people of Mumbai is uncertain as most mangrove areas
are brackish. Mangrove forests also provide protection from saline water
intrusion (Nghia, 2004) and so have a role in safeguarding upstream fresh water
provisions for both people and wildlife. Emerton and Kekulandala (2003)
estimated that Muthurajawela Marsh, 3,068 ha north of Colombo in Sri Lanka,
has a freshwater supply for local people value of 3.78 million SRRs yr
-1
(= 2.72
million INR yr
-1
corrected).
Food (e.g. crops, fruit, fish, etc.) ++ Many animals, including commercially important fish, prawns and crabs, spend a
part of their lives sheltering and feeding in the complex network of mangrove roots or
nesting and hunting on the substrates formed by the mangroves, supplying coastal
communities with a sustainable food source (ZSL, ; Lebata et al., 2012). Although a
significant proportion of the population of Mumbai is vegetarian and exploitation of
land animals is therefore less common, the Anthropological Survey of India in 1993
found that 88% of Indians are non–vegetarian, once fish is included (reported in
Asian Conversations, 2011) suggesting a high dependence on local marine food
resources. Christensen (1983) notes potentially lucrative oyster and other harvesting
use of mangroves in Thailand, while ScienceDaily (2008) reports on research led by
Marco Octavio Aburto–Oropeza that Mangrove destruction not only comes with
ecological cost, but monetary as well with $37 500 per hectare each year lost in terms
of fishery value alone. Emerton and Kekulandala (2003) estimated that
Muthurajawela Marsh, 3068 ha north of Colombo in Sri Lanka, has an agricultural
production value of 30.29 million SRRs yr
-1
. Emerton and Kekulandala (2003)
estimated that Muthurajawela Marsh, 3068 ha north of Colombo in Sri Lanka, has a
support for downstream fisheries value of 20.00 million SRRs yr
-1
and a fishing value
of 6.26 million SRRs yr
-1
. This cumulative value of agricultural, fisheries and fishing
values of 56.55 million SRRs yr
-1
equates to 40.58 million INR yr
-1
(corrected).
Further significant, albeit unquantified, value accrues from the contribution of
mangroves to seawater quality and natural features that make Mumbai important for
production of sea salt known for its high quality and their nutritional values. There
are also many small-scale fishing activities associated with mangrove systems that,
while widespread and cumulatively significant, evade quantification and valuation.
Fibre and fuel (e.g. timber, wool, etc.) ?Although fuel and fibre productivity is significant in mangrove systems, the emphasis
is on their protection of nature conservation and wider service benefits means that this
potential resource is not significantly exploited. However, the extent of informal use
for wood fuel, construction materials and other purposes is not known. Emerton and
Kekulandala (2003) estimated that Muthurajawela Marsh, 3,068 ha north of
Colombo in Sri Lanka, has a firewood value of 7.96 million SRRs yr
-1
(= 5.55 million
INR yr
-1
corrected). As harvesting firewood from the mangrove would degrade the
resource, any calculated value of firewood would need to be traded off against the
regulating services provided by a non-harvested mangrove.
Genetic resources (used for crop/stock
breeding and biotechnology)
?Uncertain
Biochemicals, natural medicines,
pharmaceuticals
?Mangroves not only supply a rich and diverse habitat for wildlife, but indigenous
peoples have relied upon mangroves for thousands of years to sustainably
provide resources including natural medicines (ZSL). Mangroves and other
plants in mangrove systems have a very wide range of medical applications
ranging from diarrhoeal to blood pressure, leprosy and epilepsy, arthritis and
wound healing, and other uses including treatments for AIDS (Kathiresan, 2000;
Thaman and Thaman, 2001).
Ornamental resources (e.g. shells,
flowers, etc.)
+Local people collect shells and other ornamental resources that are also sold in markets
Addendum service: aggregate and shell–
based construction materials
+Sand extraction and harvesting of shells for mixing with aggregates occurs widely
in the mangrove systems. However, despite its widespread reported occurrence,
this benefit is not valued here as, under the Bombay High Court’s 2005 Order,
sand extraction is disallowed as absolutely no ’non-forest’activity is permitted in
and around mangroves.
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Table 3. Regulatory services provided by Mumbai’s mangroves
Regulatory services
Ecosystem service Likely significance Description of service and, where possible, indicative value
Air quality regulation ++ Mangrove forests can a make a significant contribution to the removal of air pollutants (Nghia, 2004).
Climate regulation (local
temperature/precipitation,
GHG* sequestration, etc.)
++ Mangroves absorb carbon dioxide, storing carbon in their sediments and therefore lessening the impact
of global warming (ZSL, n.d.). Mangroves also have a role in mitigating some of the impacts of sea
level rise (Thaman and Thaman, 2001). Emerton and Kekulandala (2003) estimated that Muthurajawela
Marsh, 3068 ha north of Colombo in Sri Lanka, has a carbon sequestration value of 0.78 million SRRs yr
-1
(= 0.56 million INR yr
-1
corrected). Pendleton et al. (2012) review how observed high rates of annual
carbon sequestration in vegetated coastal ecosystems, including mangroves, may be lost with habitat
conversion releasing very large pools of previously sequestered ‘blue carbon’. They estimate this loss of
‘blue carbon’at 0.15–1.02 Pg of carbon dioxide annually, several times higher than previous estimates
accounting only for lost sequestration and amounting to 3–19% of those from deforestation globally
with an associated economic damage of $US 6–42 billion annually. However, the wider literature is
equivocal about the extent of carbon released on mangrove conversion, dependent as it is upon the
habitat that replaces mangrove. Purvaja and Ramesh (2000) found that annual average CH
4
emissions
of 5.02–15.4 mg m
2
h
1
from the sediment–water interface of wetlands on the Indian sub-continent,
contributing to overall climate forcing loads, and that these levels were exacerbated by organic pollution.
Mangroves are considered to be a minor source of both CH
4
and N
2
O in pristine environmental
condition, though anthropogenic activities can lead to a pronounced increase in greenhouse gas
emissions (Chauhan et al., 2008). Additional values associated with water temperature control
and incident UV and other radiation may be significant but have not thus far been assessed.
Water regulation
(timing and scale of run–off, flooding, etc.)
++ Mangroves make significant contributions to smoothing of hydrology. ‘Had Mumbai’sMithiriverand
Mahim creek mangroves not been destroyed by builders, fewer people would have died and the
property damage would have been dramatically less’(Soonabai Pirojsha Godrej Marine Ecology Centre, 2013).
Emerton and Kekulandala (2003) estimated that Muthurajawela Marsh, 3068 ha north of Colombo
in Sri Lanka, has a flood control value of 485.51 million SRRs yr
-1
(= 348.40 million INR yr
-1
corrected).
Natural hazard regulation
(i.e. storm protection)
++ Depending on their location, as well as their health and maturity, at least 70–90% of the energy of
wind-generated waves is absorbed by mangroves, which also provide a buffering capacity to tsunamis (ZSL).
The value of mangroves for storm protection, most graphically demonstrated by the tsunami, is
nevertheless widely recognized in other studies and reviews (for example, Nghia, 2004). Wave energy
may be reduced by 75% in the wave’s passage through 200 metres of mangrove (Massel, 1999),
and also reduce the velocity of water passing through the root barrier (Mazda et al., 1997). The magnitude
of energy absorption strongly depends on tree density, stem and root diameter, shore slope, bathymetry,
spectral characteristics of incident waves, and tidal stage upon entering the forest (Alongi, 2008).
Harada et al. (2002) determined through modelling that, compared with a range of other permeable
coastal structures, mangroves are highly effective at absorbing tsunamis and averting damage to property.
Mazda et al. (l997) report that 6 year old mangrove forests of 1.5 km width reduce the height of
sea waves from 1 m high at the open sea to 0.05 m at the coast. Hiraishi and Harada (2003) deduce
from modelling that 30 trees from 10 m
2
in a 100 m wide belt may reduce the maximum
tsunami flow pressure by more than 90% where wave height is less than 45 m.
Pest regulation ?Uncertain. While mangroves may harbour the predators of crop pests, contributing positively
to pest regulation. However, the overwhelming bulk of literature dealing with pests and mangroves
refers to pest of mangroves rather than promulgated by them (for example Li et al., 2012).
Disease regulation ++ The role of mangrove systems in purification of waste water makes a significant contribution to the
control of disease transmission (ZSL, n.d.). Mosquitoes are common perceived as a potential
problem associated with mangroves, but in reality the saline conditions means that their populations
are limited to the fresher ‘high marsh’region. In one of a series of papers addressing the mosquitoes
(Continues)
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Table 3. (Continued)
Regulatory services
of Indian mangrove systems, Rajavel et al. (2007) found 12 species of mosquito in the mangroves
of Vikhroli, Maharashtra, though nuisance and disease transmission impacts on humans were not
determined. The overall contribution to disease reduction is significant, hence the ‘++’rating,
though the unconfirmed potential of mangroves as a source of disease vectors creates some uncertainty.
Erosion regulation ++ Littoral and swamp forests are marginal in comparative extent in Maharashtra State, but are noted
as important for protection of seacoast and marine life with a significant contribution to Ecologically
Important Areas in Maharashtra (State of Environment Report for Maharashtra, 2007). Mangroves not
only help to preventing soil erosion but can also act as catalysts in reclaiming land from seas
(Chavan et al., 2011). Mangrove forests thereby help to limit coastal erosion (Nghia, 2004).
Saenger (2002) found that mangrove-vegetated shorelines are far less likely to erode than unvegetated shorelines.
In fact, rows of mangroves were planted to stabilize the coast by early generations of Maoris in
New Zealand (Vannucci, 1997). McIvor et al. (2013) explored the capacity of mangrove soil surfaces
to increase in elevation in response to local rises in sea-level, finding from historical evidence that
mangrove surface elevation through sediment trapping have kept pace with sea-level rise over
thousands of years in a number of study sites in central America. This suggests that mangroves
have the capacity to keep pace with sea-level rise contributing to coastal protection if protected from
degradation and given space to enable them to colonize landward areas. Alongi (2008) observes that
mangroves have demonstrated considerable resilience over timescales commensurate with shoreline
evolution, supported by evidence that soil accretion rates in mangrove forests are currently keeping pace
with mean sea-level rise. Mumbai’s mangrove systems were found to maintain the integrity of Mumbai’s
shoreline by trapping silt, providing a vital service to the city of Mumbai which is very prone to erosion
having been built on reclaimed land that is potentially eroded by the sea on all three sides. Reportedly,
‘Had Mumbai’s Mithi river and Mahim creek mangroves not been destroyed by builders, fewer people
would have died and the property damage would have been dramatically less’(http://www.mangroves.
godrej.com/MangrovesinMumbai.htm). This service is therefore very significant in Mumbai, and
particularly as the provision of the service is unequally distributed with the most intact mangroves
occurring along the eastern and southern edges of the city with mangroves on the western edge
having the greatest level of degradation.
Water purification and waste treatment ++ The benefits of this service are substantial. Some are captured under the provisioning service of ‘Fresh water’
and the regulatory service of ‘Disease regulation’above though, given the scale of industrial and
commercial activity as well as lack of treatment of a great deal of domestic waste, the residual treatment of
these wastewater streams is of substantial additional value. Emerton and Kekulandala (2003) estimated
that Muthurajawela Marsh, 3068 ha north of Colombo in Sri Lanka, has an industrial wastewater
treatment value of 162.31 million SRRs yr
-1
and a domestic sewage treatment value of 4.32 million
SRRs yr
-1
. This cumulative value of industrial and domestic wastewater treatment value of 166.63 million
SRRs yr
-1
equates to 119.57 million INR yr
-1
(corrected as noted above). However, given the level of industrial activity
and population size in the mega-city of Mumbai, this value is likely to be highly conservative. There are
wider values associated with this service that are not captured in these values, including offshore water
quality benefits of mangrove ecosystems (Allen, 1998), which are likely to affect a broad range of
marine ecosystem services. Furthermore, mangrove sediments also have the ability to sequester heavy
metals, radioactive isotopes and other poisonous chemicals in their anaerobic muds (Lugo and Brinson,
1978; Saenger and McConchie, 1990)
Pollination +A significant number of studies have been carried out on the diverse ways in which mangroves are
pollinated, though rather less on the wider pollination services to which they contribute.
Nevertheless, mangroves are known to attract bees and to be significant in some regions
in honey production (Krishnamurthy, 1990), with implications for the wider role of these
insects in pollinating crops and other flora.
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Table 4. Cultural services provided by Mumbai’s mangroves
Cultural services
Ecosystem service Likely significance Description of service and, where possible, indicative value
Cultural heritage +The cultural contribution of the mangroves of Mumbai are summarised as representing ‘…
the spirit of Mumbai –they are plucky survivors…’ (Soonabai Pirojsha Godrej Marine
Ecology Centre, 2013).
Recreation and tourism ++ Emerton and Kekulandala (2003) estimated that Muthurajawela Marsh, 3068ha north of Colombo
in Sri Lanka, has a recreation value of 5.28 million SRRs yr
-1
(= 3.79 million INR yr
-1
). A large
number of ‘hits’on internet searches reveal thriving angling interests in and around the mangroves
particularly for barramundi (Lates calcarifer), also known as the ‘Asian seabass’. Lack of awareness
of mangroves means that potential ecotourism opportunities have not to date been exploited.
Consumer surplus values for tourism to marine parks in the Seychelles by Mathieu et al.
(2003) and meta-analysis values for recreational values determined by Brander et al.
(2007) suggest an annual US$88 000 total (= 4.46 million INR), which is broadly comparable
with the value deduced above.
Aesthetic value +Mangroves add to the green spaces in cities (Vijayaraghavan, 2011) including, as cited previously,
the character and history of the island/coastal city of Mumbai.
Spiritual and religious value +The spiritual value of mangroves around Mumbai is uncertain, though elsewhere they are implicated
in significant spiritual values. For example, the Caribbean Regional Research Plan (2013) notes that, in
the Caribbean, the mangrove is a place of important cultural and spiritual meanings, associated with
maroon societies, deities and religious practices of African descent and heritage. The Caribbean
Regional Research Plan (2013) also highlights that mangroves are also a living metaphor of freedom,
culture and resistance in the post-colonial literature of the region.
Inspiration of art, folklore, architecture,
etc.
?Uncertain.
Social relations (e.g. fishing, grazing or
cropping communities)
+/Fishing communities and food businesses are associated with the productivity of seafood (ZSL, n.d.),
both formally and informally. However, Vijayaraghavan (2011) reports that the Bombay
Environmental Action Group (BEAG) played an instrumental role in protecting urban
mangroves, filing a public interest litigation suit in the high court to protect them. Furthermore,
there is a Mumbai chapter of the Mangrove Society of India (http://mumbaimangroves.
wordpress.com/) which is active in voluntary monitoring, conservation, and campaigning about
Mumbai’s mangrove resource. This cumulatively indicates significant public mobilization about the
value of the mangroves of Mumbai. Conversely, many industries and residents in Mumbai
regard mangroves as places to dispose of waste, suggesting that this social value remains
far from ubiquitous.
Addendum service: Educational resources ?There is a large body of interest in mangrove research around the world, in addition to potential for
mangroves to provide an education resource for local schools, people, and researchers. This resource seems to be
substantially underexploited at present in the Mumbai area.
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Table 5. Supporting services provided by Mumbai’s mangroves
Supporting services
Ecosystem service Likely significance Description of service and, where possible, indicative value
Soil formation +Soil formation is noted as a significant service provided by mangrove systems (ZSL).
Mangroves not only help to preventing soil erosion but also act as catalysts
in reclaiming land from seas (Chavan et al., 2011).
Primary production ++ Mangroves amongst the world’s most productive ecosystems per unit area (Harrison, 1967),
contributing significantly to primary production locally though they only represent
some 0.7% of tropical forest area so the net global contribution may be small.
Nutrient cycling ++ The habitat diversity of mangrove systems, including juxtapositions of aerobic and
anaerobic regions, enables mangrove systems to recycle nutrients efficiently. Mangroves also
serve as a sink for high nitrate and phosphate levels coming off the land (Ellison, 2001).
Water recycling ++ Water recapture within the complex vegetation structure of mangroves makes them
highly efficient in short-scale water recycling.
Photosynthesis
(production of atmospheric oxygen)
++ Mangroves are among the world’s most productive ecosystems (Harrison, 1967),
contributing significantly to photosynthesis and the generation of oxygen.
Provision of habitat ++ Mangrove systems provide a wide range of habitat for a range of organisms.
This includes many animal species. These include commercially important fish,
prawns and crabs, which spend a part of their lives sheltering and feeding in the
complex network of mangrove roots or nesting and hunting on the substrates formed
by the mangroves, supplying coastal communities with a sustainable food source (ZSL).
Littoral and swamp forests are marginal in comparative extent in Maharashtra State,
but are noted as important for protection of seacoast and marine life with a
significant contribution to Ecologically Important Areas in Maharashtra (State of
Environment Report for Maharashtra 2007). The mangroves of Mumbai were
reported to attract nearly 206 species of birds, 35–40 reptiles, 16 crabs, at least three
types of prawns and several fish species, while transition forests also serve as
habitat for mammals, including jackals, mongoose, wild boars, feral boars (a hybrid)
and panthers in some regions (Mangrove Action Project, 2008). Mangrove forest
are also recognized as important ecosystems in tropical coastal areas providing habitats
for various species, nursery areas of fish species, for water birds, and for migrating birds (Nghia, 2004).
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cumulative socio-economic value of non-monetized
services may potentially dwarf that of monetized
services. Lack of capacity to value the full range of
benefits may weaken the case for conservation and
the protection of longer-term human interest; Lal
(2003) suggests that, for advocacy purposes
and particularly when large areas are involved,
communicating the total economic value of
mangroves is influential.
In addition, it is important to recognize that
mangroves do not exist in isolation, but are an
ecotone between marine/estuarine and terrestrial
habitats. In particular, closely connected extensive
mudflats support additional biodiversity including
migratory birds and food for fish of value to people,
as well as providing a range of associated services of
benefit to humanity. Valuation of closely linked
habitat types was not explicitly included in the
present analysis, although implicitly some will have
been in transferring values from the Emerton and
Kekulandala (2003) study which took account of a
range of coastal habitat types. Neither are the values
of periodically inundated areas to the landward side
of the mangroves, nor of nullahs (drains or streams)
that flow through these systems, considered despite
their close linkages and likelihood to provide many
related services. Further source studies addressing
the functional links and associated services between
mangroves and adjacent habitats, apparently
lacking at present in the literature, would add
significant value to the system as a whole.
Taking account of both the many non-monetized
benefits and considering the additional value of
intimately connected habitats, the cumulative
value of Mumbai’s mangroves is likely to be an
order, or perhaps orders, of magnitude greater
than the cumulative total of the six services that
have been partially monetized.
Aggregated ecosystem services values for various
habitat types, though widely used, are fraught with
difficulties including context-dependence and
coverage across ecosystem service categories. Some
other studies have sought to derive cumulative
values for the ecosystem services provided
specifically by mangroves. For example, a report by
UNEP–WCMC (2006) estimates that the value of
ecosystem services provided by mangrove forests
exceeds US$100 000 km
–2
yr
–1
(US$1000 ha
–1
yr
–1
or
0.051 million INR ha
–1
yr
–1
)inAmericanSamoa,
and US$3.5 million km
–2
yr
–1
(US$35 000 ha
–1
yr
–1
or 1.77 million INR ha
–1
yr
–1
) in Thailand, while in
Matang, Malaysia, a 400km
2
managed mangrove
forest was found to support a fishery worth US$100
million a year with further income from forestry
products of US$10 million a year. Vijayaraghavan
(2011) records that the ecosystem services that
mangroves provide are ‘tremendous’,valuedat
anywhere between $2000 and $9000 ha
–1
annually in
terms of their roles in tidal and waves protection and
as carbon sinks. Vijayaraghavan (2011) cites an
indicative annual value estimate of cost savings by
the city of Mumbai US$52 million, though no source
is cited for the underlying analysis. And, as deduced
earlier in this paper, simplistic extrapolation of
meta-analytic data values suggests annual service
benefits to the Mumbai city-region from its
mangroves of US$23.6 million (1204 million INR
basedontheBranderet al. (2012) (mean value), US
$1.3 million (66.3 million INR based on the Brander
et al. (2012) median value) and US$69.9 million (3550
INR extrapolated from the Barbier (2007) estimate).
All of these attempts to derive aggregated
mangrove values, in the order of US$ tens of
million annually, are not substantially adrift from
indicative values for Mumbai’s mangroves. The
0.051 million INR ha
–1
yr
–1
value for American
Samoa and the 1.77 million INR ha
–1
yr
–1
value
for Thailand equate to total benefits of 288 million
INR yr
–1
and 9983 million INR yr
–1
respectively
when multiplied by the area of Mumbai’s
mangroves. This is comparable with the
Vijayaraghavan (2011) value of 2700 million INR
yr
–1
. It is also proportionate with the 515.62 million
INR yr
–1
value for services that could be monetized
as calculated from this study, although of course this
sum addresses only the more readily-valued
ecosystem services associated with Mumbai’s
mangroves. Of the 29 ecosystem services assessed on
a semi-quantitative basis, 15 (52%) were considered
to be ‘significantly positive’, 9 (31%) were assessed as
‘positive’and 7 (24%) as ‘unknown/uncertain’,with
none found to be ‘neutral’,‘negative’or ‘significantly
negative’. It was not possible to monetize many of
these beneficial services, and they have also generally
been omitted in earlier economic analyses. All of
these monetization studies are therefore necessarily
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highly conservative representing as they do a
substantial underestimation of the likely cumulative
value of mangrove systems, due largely to a lack of
prior valuation studies or knowledge gaps about how
all services are produced, both of which therefore
represent significant research needs if mangroves are
to be appropriately valued and protected.
Having acknowledged considerable uncertainties,
the conservative aggregate value of 515.62 million
INR yr
–1
calculated in this study serves for
illustrative purposes the magnitude of value provided
to the Mumbai city-region by its fringing mangroves.
It represents a value of 0.09 million INR yr
–1
(US$
135 yr
–1
) for every hectare of existing mangrove.
Even assuming an unrealistically short lifetime value
of 25 years, with a discount rate of 3.5%, the
cumulative value of Mumbai’s mangroves equals in
the order of 8.7 billion INR (US$ 0.13 billion), or
nearly 1.54 million INR ha
–1
(£UK 23 000 ha
–1
). In
reality, this too is a highly conservative figure as not
only is the ‘lifetime’benefitofmangrovesfarmore
long-lasting, and may in fact increase in value rather
than be discounted, as emerging challenges such as
climate change and food security amplify a number
of benefits including buffering against sea level rise,
the likelihood of increasing storms and potentially
tsunamis, and local food provision.
Another factor influencing the value of mangroves
to the Mumbai city-region is their distribution. The
distribution of ‘Reserved’mangroves in the Greater
Mumbai area, noted previously as reported in the
Times of India (2013), includes 277 ha in the island
city, 3720 ha in the suburbs and 1471 ha in Navi
Mumbai. It is notable that the 277ha of mangroves
in the island city surround not merely the densest
centre of population and built infrastructure but
also the highest real estate values, so historical loss
and current paucity may significantly amplify the
value of extant and restored mangroves. It is not
possible to quantify this distributional impact based
on currently available data, so this may constitute a
significant research priority.
Mangroves and future development of the
Mumbai City
Although comparing the 2010 development land
value of 81.8 million INR ha
–1
(US$ 1.23 ha
–1
)
with a conservative mangrove ecosystem service
value of 1.54 million INR ha
–1
(£UK 23 000 ha
–1
)
has no objective scientific basis, it nevertheless
serves to emphasize the magnitude of the
contribution of Mumbai’s mangrove ‘natural
infrastructure’(sensu Everard, 2013) and the
‘insurance’that it provides for the built
environment of Mumbai. This also demonstrates
the continuing value of mangrove conservation
and the importance of not releasing further land
for development. Conversely, if these ecosystem
service values are lost through unsympathetic
development of mangroves, they are likely to be
paid as a ‘tax’on urban health, damage to life and
property, loss of fishery and other economic
opportunity, etc., with disproportionate costs
incurred by future generations. The implications of
observed losses may be significant; Brander et al.
(2012) found that, under a baseline scenario of
mangrove loss for the period 2000–2050, annual
benefits foregone in 2050 are between US$ 1.6 and
2.8 billion in south-east Asia. A progressive
pattern of loss, notwithstanding recent attempts to
halt the decline, may mean that Mumbai’s
remaining mangroves are disproportionately more
valuable, though clearly the relationship will be far
from linear with some services degrading quicker
than others as critical minima of habitat extent
and distribution are reached.
The implications are clear that the conservation
of mangroves is a wise investment in the future
security of the city, including its health and
economy, providing ’headroom’for future security
and growth. Indeed, taking account of these highly
conservative ecosystem service benefits, Mumbai’s
remaining mangroves may be among the most
valuable real estate in the city region taking
account of the protection and other values they
afford. This observation warrants the increasing
levels of protection of the mangrove systems of
Mumbai and its environs, and the need for further
research to focus and cost-justify continued
conservation efforts.
Restoration of degraded systems, including habitat
lost to illegal encroachment, may be a wise means to
invest in the natural capital underpinning future
human wellbeing and opportunity. There have been
instances of mangrove system restoration, for
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example in Singapore as part of mitigation for
development (Tatani et al., 2001), but further study
of value realization from restoration is required. This
value to the city is tangible and needs to be
understood and appreciated, unlike many more rural
locations. Averting continuing loss is an absolute
priority as even if the multiple benefits provided by
mangroves could be replaced, restoration costs
would be likely to outstrip the resources for most
Pacific island rural and urban communities (Thaman
and Thaman, 2001). However, it is essential that
mangrove restoration is sited appropriately and that
mitigation measures are realistic, and that mitigation
for damage from development is genuinely
compensatory based on ecological logic and not,
for example, planting non-mangrove species as
mitigation for loss of mangroves (Chavan et al.,
2011). Kaujalgi (2010) proposes a process for
the development of a mangrove mitigation plan for
the city of Mumbai, assessing the potential
mangrove stand which may be restored and why this
is necessary; this thesis recommends mangrove
conservation and restoration policies for Mumbai
based on the multiple benefits these ecosystems
provide, informed by studies in other countries.
In addition to the compelling case for the
protection and rehabilitation of mangroves, it may
also be important to invest in space for mangrove
migration and regeneration where mangroves are
not currently present. Sea-level rise and other
impacts associated with climate change, as well as
natural geomorphological processes, mean that it
is important to provide mangrove systems with
space to move. Current climate change trends may
lead to a maximum global loss of 10–15% of
mangrove forest, although this is of secondary
importance compared with current average annual
rates of 1–2% deforestation (Alongi, 2008).
An economic basis for mangrove protection
and restoration
Beyond clear and cross-disciplinary ‘likelihood of
impact’benefits stemming from mangrove
protection addressed by this paper, there also
appears to be a substantial economic case for the
regeneration or reinstatement of lost mangroves.
As observed, the current distribution of mangroves
appears inversely proportional to the density
and value of built infrastructure, and this is
particularly so towards the seaward (western)
shore of Mumbai where the greatest value would
be accrued from protection. Means to restore
mangroves might include direct action by the
municipality of Mumbai or by influential
environmental NGOs, by developers recognizing
and wishing to accrue some of the benefits of
ecosystem services such as storm protection, access
to green spaces and treatment of poor water
quality entering the coastal zone via nullahs
(streams that have been treated as open sewers), or
as ‘planning gain’representing a partnership
between development and planning sectors.
Innovative ‘payment for ecosystem services’
(PES) markets offer an emerging means, now
widespread across the world and addressing many
focal ecosystem services, to internalize the value of
the services of ecosystems into mainstream
economic systems (OECD, 2010). The prime PES
‘market’opportunity for Mumbai’s mangrove
systems would appear to be for storm protection
of built infrastructure, and there may be direct
‘buyers’of these services including municipalities
and developers. However, additional services and
buyers could be packaged into emerging PES
markets whether through ‘bundling’(where a single
buyer or consortium pays for a package of
ecosystem services), ‘layering’(multiple buyers pay
for separate ecosystem services arising from
management of the same resource) or ‘piggy-
backing’(one or a few services are sold as an
‘umbrella’and other services ‘free ride’)(Smithet al.,
2013). Further exploration of opportunities for
regeneration of lost or degraded natural capital,
particularly in the regions of greatest historic
mangrove loss, are beyond the scope of this paper
but represent important research needs that may be
crucial for better protection of the long-term interests
of Mumbai municipality and its built environment.
Economic valuation, even in outline terms, can
be persuasive. For example, in Fiji, a rough
estimate of the economic value of mangrove
resources was reported to be the single most
powerful piece of information convincing the
minister responsible for land development to place
a moratorium on the large-scale reclamation of
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mangroves in 1983 (Lal, 2001). However, as
illustrated by the highly conservative and partial
nature of monetization in this study, these
economic assessments should not be taken as of
absolute value, but rather as indicators of the scale
of likely impacts. This is further reinforced by the
fact that a unit increase in mangrove habitat area
cannot be assumed to produce a linear increase in
the value of services such as storm protection
owing to non-linearities in wave attenuation,
thus introducing uncertainties if simplistic linear
assumptions about value are applied (Barbier
et al., 2008). Furthermore, it has not been possible
to determine values for all mangrove services in
this assessment, and appreciation of the value of
many services associated with coastal habitats may
change over time (Everard et al., 2010). Neither
can generalizations be safely made about
permissible percentages of habitat conversion, as
current service loss may already be close to an
unforeseeable tipping point (Barbier et al., 2008).
Additional opportunities for realizing the societal
value of mangroves in urban contexts, including
in the Mumbai city-region, may stem from
development of non-destructive ecotourism and
educational potential, including wider public
understanding of the values that they provide. There
is already some progress being made here, including
for example a reported recent increase in the
awareness of the people in Mumbai about
potentially far-reaching effects that may stem from
the trend of mangrove loss, with local NGOs active
in highlighting issues such as land reclamation,
coastal regulation zone notification and illegal
destruction of the mangrove areas (http://www.
mangroves.godrej.com/MangrovesinMumbai.htm).
Continuing threats from development pressures
for values associated with various ecosystem services
are beginning to be better appreciated and prioritized
by city planning authorities. This includes, for
example, the Brihanmumbai Municipal Corporation
(BMC), which is making an amendment to its civic
budget to introduce ’Open Space Mumbai’,tablinga
proposal for a 5-year programme to recognize and
invest in natural assets, explicitly including
mangroves and creeks, and to inspire greater public
appreciation of natural assets as Mumbai’s‘prized
possessions’(Baliga, 2012).
Siikamäki et al. (2012) recognize the global
economic potential for protecting mangroves based
exclusively on carbon sequestration, which could be
realized for less than US$10 ton
–1
CO
2
. (This is
higher than the value current at the time of writing
of around US$6 ton
–1
.) Siikamäki et al. (2012)
suggest that a US$10 value would makes this
strategy economically viable, though a narrow focus
on carbon conservation does not automatically
target areas most valuable for biodiversity.
Warren-Rhodes et al. (2011) also highlight the
potential for protection and restoration of
mangroves through payments for ecosystem services
(PES) schemes that also contribute to improved
livelihoods, climate mitigation and adaptation.
However, both sets of authors also recognize
practical barriers to scheme development,
particularly in a developing-world context.
Taking account of disservices
Of course, not all ecosystem services impacts are
uniformly positive. For example, consideration of
disease regulation in Table 3 recognizes that,
alongside the known role of mangrove systems in
purification of waste water making a significant
positive contribution to controlling disease
transmission, the potential for hosting disease
vectors such as mosquitoes in the ‘high marsh’
region is acknowledged but unconfirmed in
the literature. Also, the potential for methane
and nitrous oxide generation is acknowledged
alongside significant rates of carbon sequestration,
albeit assumed with some uncertainty to be of low
importance (Table 3).
Furthermore, were the harvesting of mangroves for
subsistence and cash purposes not now to be banned
in the ‘Reserved’mangroves of Mumbai, harvesting
activities would potentially reverse the benefits of
some services such as erosion control and carbon
sequestration resulting in potentially significant
disservices. Table 3 also reviews literature suggesting
that organic pollution of mangroves can exacerbate
their potential to generate methane and nitrous
oxide. Mangrove management, including their
conservation, then constitutes an important
determinant of the overall balance of benefits that
these systems provide.
M. EVERARD ET AL.270
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Further research
Knowledge gaps limit the robust quantification and
valuation of the services provided by mangrove
systems, therefore representing priority research
needs to support conservation of mangroves and
their multiple benefits to society.
The most obvious research need is for more primary
valuation studies addressing mangrove systems. These
may be specifically germane to India, but are likely to
be of generic relevance across the tropical and sub-
tropical range where mangrove systems occur. While
meta-analyses of multiple services have some value,
the greatest insight and transferability will be
achieved where services are valued discretely.
Furthermore, far greater attention needs to be
devoted to valuation of services for which there is no
current market or no effective market proxies as it is
these services, generally supporting and regulatory
services as well as cultural services enjoyed by less
politically and economically influential communities.
This includes not merely economic studies, but also
developing better understanding of how these
ecosystem service benefits are generated. These more
elusive services are most commonly overlooked in
decision-making and cost-benefit appraisals,
potentially perpetuating degradation of habitats and
their range of beneficial services.
More research is also evidently needed to address
linkages between mangroves and other adjacent
habitats, and the processes occurring through their
interactions (for example fish recruitment into the
coastal zone from high salt marshes and mangrove
systems) may be of significant but potentially
overlooked value.
More research is also required into the spatial
delivery of ecosystem services from mangrove
systems, and how this relates to observed mangrove
distribution. For example, it was noted that the
smallest area mangroves occurred closest to the
densest and highest-value built infrastructure,
potentially exposing the city-region to greater
vulnerability to storm surges, wave damage and
other threats exacerbated by loss of regulatory
services. More research is also required to address
critical thresholds of aerial extent for delivery of
different services, as well as internal diversification
of structure within mangrove and associated
mudflat and terrestrial systems. As observed in the
case of pollution and the regeneration and
movement in response to climate change and
geomorphological processes, more knowledge is
required to inform strategic and optimally beneficial
management of mangrove systems.
Research is also required to address synergies and
antagonisms between exploitation of ecosystem
services, and the consequent implications for
sustainability and the societal value of practices and
policies. For example, as discussed as a rationale for
excluding the deduced service of ‘fibre and fuel’
from valuation of Mumbai’s mangrove systems,
there is potential for interactions –synergistic as
well as antagonistic –between the appropriation of
different services, and hence a requirement for
informed consideration about sustainable options
and the safeguarding of critical services such as
erosion control and storm/hazard protection. These
multiple potential synergies and trade-offs are under-
researched at present in mangroves, as indeed in
many other ecosystems. Information relating
to ecological changes stemming from domestic
pollution indicates potentially significant interactions
between services in mangroves (Amaral et al., 2009).
Further research needs to take account of
distributional impacts of costs and benefits among
the diversity of beneficiaries, including spatial
variation in the delivery of services. This relates
particularly to differences on either side of the
Mumbai peninsula.
Such research should incorporate a Mumbai-
specific application of what are generically based
estimates of the indicative ecosystem service values
listed above and should, if possible, provide an
indication of trends in those services before the 1991
CRZ notification and subsequently in order to
deduce implications for human wellbeing.
Generic lessons
Many of the Mumbai-specific conclusions presented
in this paper are drawn from mangrove systems
across the tropical and sub-tropical range where
they occur as ecotones between coastal/estuarine
and terrestrial habitats. It is equally the case that
conclusions drawn in this paper have more generic
applicability to other mangrove systems.
THE BENEFITS OF FRINGING MANGROVE SYSTEMS TO MUMBAI 271
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The key generic lessons therefore include the need
for more effective valuation, in both monetary and
other terms, of the diverse benefits provided by
mangrove systems including their interdependencies
with adjacent habitats. Translation of these values
into policy-relevant terms can justify protective
policy responses currently in place, and also help
support and steer increasingly effective conservation
measures that safeguard and portray mangrove
systems as valuable ‘natural infrastructure’.This
value then needs to be factored into city
development, not merely as a perceived constraint of
future development but as internalization as value-
added natural infrastructure providing multiple
services beneficial to the city in terms, for example,
of amenity, food resources, storm and tidal
surge protection, visual and noise buffering,
microclimate and air quality regulation, aesthetics,
and natural drainage.
Policy then needs to evolve as not merely
representing a set of prohibitions, though this will
be essential where a critical minimum of habitat
warrants focused protection, but in terms of
‘mainstreaming’the value of natural systems such
as mangroves across policy areas. This may open
up opportunities for using emerging market-based
instruments, such as ‘payments for ecosystem
services’(PES), to incorporate these values into
future development.
Mangrove protection and value realization,
across the wide geographical range in which such
systems occur, would benefit from investment in
research to address how these systems function,
interact with adjacent habitats and produce
multiple services. This research should also be
helpful in expressing the value of services and
goods provide by mangrove systems, feeding back
into wise management policies for the optimal,
long-term benefit to all in society.
ACKNOWLEDGEMENTS
The authors are grateful to Tim Pagella, Charlie
Falzon and Shiva Chavan for contributing to the
assessment of likely impacts on ecosystem services
of mangrove systems in Mumbai, and to Tim
Pagella for drawing the GIS base map used to
develop Figure 1.
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