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The benefits of fringing mangrove systems to Mumbai

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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.
Everard, M., Jha, R.R.S. and Russell, S. (2014). The benefits of fringing mangrove systems
to Mumbai. Aquatic Conservation: Marine and Freshwater Ecosystems, 24, pp.256–274.
The benefits of fringing mangrove systems to Mumbai
EVERARD, M., JHA, R.R.S. and RUSSELL, S.
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.
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 (CRZ) was notified across India, initially in 1991 but substantially
Everard, M., Jha, R.R.S. and Russell, S. (2014). The benefits of fringing mangrove systems
to Mumbai. Aquatic Conservation: Marine and Freshwater Ecosystems, 24, pp.256–274.
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 50m 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)1.
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
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 INRm–2 for land
(Business Standard,
2010). (81.8 million INR ha–1 equates approximately to $US 1.56 million or £0.96 million at April 2012 exchange
rates).
Everard, M., Jha, R.R.S. and Russell, S. (2014). The benefits of fringing mangrove systems
to Mumbai. Aquatic Conservation: Marine and Freshwater Ecosystems, 24, pp.256–274.
including protection from natural hazards such as storm surges and tsunamis.
Indeed, Danielsen etal. (2005) found ‘markedly less’ damage to areas inland from
the coast shielded from the impacts of the 2004 Indian Ocean Tsunami by coastal
tree vegetation. This was among the most devastating natural disasters in recent
history killing 229 866 people and causing billions of US$ in damage (United
Nations, 2007), with mangroves constituting the most important protective coastal
tree vegetation in the area. Villag es 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 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 et al., 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 1 ha 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
Everard, M., Jha, R.R.S. and Russell, S. (2014). The benefits of fringing mangrove systems
to Mumbai. Aquatic Conservation: Marine and Freshwater Ecosystems, 24, pp.256–274.
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
km2 (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 km2 (2220 ha). However, Table 1 provides
survey data published by Vijay et al. (2005) suggesting 56.4 km2 (5640 ha) of extant
mangroves including both ‘dense’ and ‘sparse’ stands. Time series data reproduced
from Vijay et al. (2005) in Table 1 substantiates perceptions about a sharp decline of
mangrove extent throughout the last decade of the 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 km2 of mangroves in
Mumbai and its neighbouring areas, of which more than 5800 hectares (58 km2) was
protected forests (Vijayaraghavan, 2011). Recent satellite data indicates that
Mumbai and its adjoining areas have, at present, 61.7 km2 (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
Everard, M., Jha, R.R.S. and Russell, S. (2014). The benefits of fringing mangrove systems
to Mumbai. Aquatic Conservation: Marine and Freshwater Ecosystems, 24, pp.256–274.
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 km2) 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 km2 to 6.2 km2). 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 km2 (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.
Table 1: Area under mangrove in Mumbai (from Vijay et al., 2005)
Year Mangrove classes (km2)
Sparse mangroves Dense mangroves Total area (km2)
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%)
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 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
Everard, M., Jha, R.R.S. and Russell, S. (2014). The benefits of fringing mangrove systems
to Mumbai. Aquatic Conservation: Marine and Freshwater Ecosystems, 24, pp.256–274.
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 for present-day values as such a
correction was 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
‘0’ Neutral
‘-‘ Negative
Everard, M., Jha, R.R.S. and Russell, S. (2014). The benefits of fringing mangrove systems
to Mumbai. Aquatic Conservation: Marine and Freshwater Ecosystems, 24, pp.256–274.
‘- -‘ 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.
Table 2. Provisioning services provided by Mumbai’s mangroves
Provisioning services
Ecosystem
service
Likely
significanc
e
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
Everard, M., Jha, R.R.S. and Russell, S. (2014). The benefits of fringing mangrove systems
to Mumbai. Aquatic Conservation: Marine and Freshwater Ecosystems, 24, pp.256–274.
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.
Table 3. Regulatory services provided by Mumbai’s mangroves
Regulatory services
Ecosystem service Likely
significanc
e
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/precipitatio
n, 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
Everard, M., Jha, R.R.S. and Russell, S. (2014). The benefits of fringing mangrove systems
to Mumbai. Aquatic Conservation: Marine and Freshwater Ecosystems, 24, pp.256–274.
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 CH4 emissions of 5.02–
15.4mgm_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 CH4 and N2O 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’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’ (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 1m high at the open sea to 0.05m at the
coast. Hiraishi and Harada (2003) deduce from modelling
that 30 trees from 10m2 in a 100m wide belt may reduce
the maximum tsunami flow pressure by more than 90%
Everard, M., Jha, R.R.S. and Russell, S. (2014). The benefits of fringing mangrove systems
to Mumbai. Aquatic Conservation: Marine and Freshwater Ecosystems, 24, pp.256–274.
where wave height is less than 45m.
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 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.ht
m). This service is therefore very significant in Mumbai,
Everard, M., Jha, R.R.S. and Russell, S. (2014). The benefits of fringing mangrove systems
to Mumbai. Aquatic Conservation: Marine and Freshwater Ecosystems, 24, pp.256–274.
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.
Table 4. Cultural services provided by Mumbai’s mangroves
Regulatory services
Ecosystem
service
Likely
significanc
e
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, 3068 ha 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
Everard, M., Jha, R.R.S. and Russell, S. (2014). The benefits of fringing mangrove systems
to Mumbai. Aquatic Conservation: Marine and Freshwater Ecosystems, 24, pp.256–274.
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.
Table 5. Supporting services provided by Mumbai’s mangroves
Regulatory services
Ecosystem
service
Likely
significanc
e
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
Everard, M., Jha, R.R.S. and Russell, S. (2014). The benefits of fringing mangrove systems
to Mumbai. Aquatic Conservation: Marine and Freshwater Ecosystems, 24, pp.256–274.
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).
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’ is not used to
assess overall 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
Everard, M., Jha, R.R.S. and Russell, S. (2014). The benefits of fringing mangrove systems
to Mumbai. Aquatic Conservation: Marine and Freshwater Ecosystems, 24, pp.256–274.
‘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’, which may be a
significant, as well as a significantly 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 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
Everard, M., Jha, R.R.S. and Russell, S. (2014). The benefits of fringing mangrove systems
to Mumbai. Aquatic Conservation: Marine and Freshwater Ecosystems, 24, pp.256–274.
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 000km–2 yr–1 (US$1000 ha–1 yr–1
or 0.051 million INR ha–1 yr–1) in American Samoa, 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 400 km2 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’, valued at 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 based on the Brander et 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 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
Everard, M., Jha, R.R.S. and Russell, S. (2014). The benefits of fringing mangrove systems
to Mumbai. Aquatic Conservation: Marine and Freshwater Ecosystems, 24, pp.256–274.
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’ benefit of
mangroves far more 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
277 ha 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.
Everard, M., Jha, R.R.S. and Russell, S. (2014). The benefits of fringing mangrove systems
to Mumbai. Aquatic Conservation: Marine and Freshwater Ecosystems, 24, pp.256–274.
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
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
Everard, M., Jha, R.R.S. and Russell, S. (2014). The benefits of fringing mangrove systems
to Mumbai. Aquatic Conservation: Marine and Freshwater Ecosystems, 24, pp.256–274.
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 ‘piggybacking’ (one or a few services are sold as an ‘umbrella’ and other
services ‘free ride’) (Smith et 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 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).
Everard, M., Jha, R.R.S. and Russell, S. (2014). The benefits of fringing mangrove systems
to Mumbai. Aquatic Conservation: Marine and Freshwater Ecosystems, 24, pp.256–274.
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’, tabling a 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 CO2. (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.
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.
Everard, M., Jha, R.R.S. and Russell, S. (2014). The benefits of fringing mangrove systems
to Mumbai. Aquatic Conservation: Marine and Freshwater Ecosystems, 24, pp.256–274.
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 subtropical 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
Everard, M., Jha, R.R.S. and Russell, S. (2014). The benefits of fringing mangrove systems
to Mumbai. Aquatic Conservation: Marine and Freshwater Ecosystems, 24, pp.256–274.
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 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.
Everard, M., Jha, R.R.S. and Russell, S. (2014). The benefits of fringing mangrove systems
to Mumbai. Aquatic Conservation: Marine and Freshwater Ecosystems, 24, pp.256–274.
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... Given the continued trend of urban expansion in the tropics (Neumann et al., 2015), such developmental pressures are likely to continue to threaten mangroves in the future. The survival of mangroves and the ecosystem services they provide to urban communities are thus being increasingly appreciated (Branoff, 2017;Everard et al., 2014). ...
... Disturbed mangroves in urban landscapes such as in Kenya and Mumbai often experience fragmentation, thinning, and low vegetation density due to continual unmanaged exploitation, pollution, and development within and around mangrove forests (Everard et al., 2014;Mohamed et al., 2009). Such small patches can still provide ecosystem services (Curnick et al., 2019), but degradation may reduce the ability of mangroves to attenuate waves, and protect coasts (McIvor et al., 2012). ...
Article
Mangroves are able to protect coastal communities through their ability to attenuate incoming long and short wave energy. Evidence of wave attenuation function and the factors contributing to wave attenuation by mangroves are now well established, especially for undisturbed mangrove stands. However, as tropical coastlines continue to urbanize rapidly, there is interest in understanding the ability of mangroves in wave attenuation along such disturbed coastlines. This study models the potential wave attenuation capacity of disturbed mangroves along the urban coastline of Singapore. Short wave attenuation is estimated under both average and storm (elevated water level) conditions. The percentage of wave height reduction is higher under storm events compared to average conditions. Vegetation drag is the main mechanism of wave energy dissipation under both average and storm conditions, with additional wave dissipation caused by wave breaking under the latter. Mangrove density and width were found to be positively correlated to the percentage of wave height reduction during a storm event. Compared to trunks and canopies, mangrove roots contributed to a larger percentage of wave height reduction. No statistical differences in wave height reduction extent were found between mangrove types, incident wave heights, and water levels respectively. This study has illustrated the potential for the attenuation of short waves by disturbed mangroves, especially during elevated water levels associated with storm events. The findings imply the potential of disturbed mangroves in wave attenuation, and should encourage the stronger incorporation of mangroves into coastal management strategies designed to protect communities against coastal hazards.
... Mangroves in Mumbai store 2,38,417 tonnes of carbon, primarily from pollutants released into the atmosphere by human activities (Hindustan Times 13 th July, 2015), thereby sinking the atmospheric pollution and keeping better air quality compared with other metro cities like Delhi (WHO, 2014). Mumbai has probably lost 40% of all its mangroves in the past decade or so, mainly due to growing population pressure, construction and development activities, conversion to agricultural land and fish farms, besides the effect of industrial effluents (Everard et al., 2014). Mangrove cover in Maharashtra over three decades by the FSI showed a considerable increase since 1999 (approximately 108 km 2 in 1999 to 304 km 2 in 2017) ( Supplementary Fig. 3 J o u r n a l P r e -p r o o f ...
Article
Mangroves are one of the world threatened ecosystems, which is protected and categorised under CRZ-I according to the Coastal Regulation Zone (CRZ) notification. The present study marked the decadal (1990–2017, Landsat series) change of mangroves and mapped the species distribution (2017, Sentinel-2) around Thane creek, Mumbai using SMLC with QGIS-SCP software. ADCIRC model was used to simulate the tidal flooding/ebbing towards mangroves, and the model was validated with the in-situ observation of tides and currents. From 1990 to 2017, the mangrove area increased from 79.14 km² to 154.5 km² and expanded towards landward and seaward regions. Between 2010 and 2017, there was a fluctuation in the mangrove area with ups and downs in their distribution caused by different climatic conditions and anthropogenic activities. The increase in built-up area was two times than mangrove area increase. The dominance of Avicennia marina species confirms the increased anthropogenic activity along the landward side. To understand the response of mangroves to the tidal dynamics, the model was simulated with two scenarios; with mangroves and without mangroves. In the absence of mangroves (without mangroves), Thane Creek demonstrated a perfect funnelling effect by increased tidal amplification with strong flood currents, resulting in severe coastal inundation and erosion. While with mangroves, tidal currents attenuated 80% of its magnitude and favoured the sediment deposition in mangrove areas, which further enhanced mangrove growth, thereby stabilising the coast. The present study has found that the mangroves in the Thane creek are in the saturation stage and reached the maximum growth towards the landward. The study envisages that the stakeholders should adopt a proper management plan for the restoration of mangroves. The highlight of the present study is the combination of satellite imagery and hydrodynamic modelling. Satellite imagery provides the estimated extent of the mangroves, and this information will be used when simulating the model, which provides maximum inundation and attenuation. The utilisation of LULC classification and ADCIRC model results would be helpful to examine the threatening built-up area due to the tidal inundation. The combination of satellite classification and hydrodynamic model findings will be decisive for management authorities towards the conservation and regeneration activities for a balanced mangrove-creek ecosystem.
... However, mangrove ecosystem services have been specifically studied only in a select number of coastal cities. For example, for Mumbai, India, Everard et al. (2014) assessed 23 provisioning, regulating and cultural services of mangroves, several of which overlap with ecosystem services quantified in this study. However, these ecosystem services were assessed in an often semi-quantitative manner from previous literature or reports, and importantly, they were considered in relative isolation, with little discussion of overlaps or synergies between individual ecosystem services. ...
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As urbanisation pressures on ecosystems are set to increase, trade-offs between ecosystem service are also likely to increase. Management strategies that minimise trade-offs and promote sustainable development to optimise ecosystem multi-functionality are therefore needed. Many coastal cities may however struggle to find the resources and capacity to operationalise ecosystem service agendas. Therefore, the objective of this study is to propose and test the suitability of a multi-functional landscape approach to ecosystem service assessments using the case study of Singapore, with focus on five ecosystem services: water and air pollution control, global climate, local temperature and recreational potential services. Our results show clear heterogeneity in the capacity of mangroves to supply different ecosystem services, with a general tendency for greater amounts of supply in larger mangrove patches, and for ecosystem services to aggregate producing hotspots of supply. Overall, a 24% of the mangrove landscape supported aggregations of at least one, two or three ecosystem services, but only <1% of the mangrove landscape supporting overlapping aggregations of all five services. Ecosystem services also co-varied to produce trade-offs and synergies, with ecosystem service bundling largely driven by regulating services. Areas of ecosystem service synergy and hotsport overlap represent possible priority areas of future conservation or management, and highlight what might be lost if significant degradation were allowed to occur. Further, the large spatial mismatch among ecosystem service hotspots also highlights the difficulty in identifying single areas capable of delivering substantial amounts of multiple ecosystem services. We conclude that this framework provides a basis to look at ecosystem services in combination, as well as individually, and to do so in a spatially explicit manner than can be overlaid with maps of land use or other development planning.
... Other large coastal cities, such as Mumbai, Singapore and Hong Kong, have substantial mangroves. Maintaining mangroves within urban landscapes has multiple benefits, including coastal protection, flood control, nutrient processing, carbon storage and cultural services ( Everard et al. 2014, Friess et al. 2016b). However, degraded coastal wetlands within city landscapes can also be sources of contaminated seafood ( Dsikowitzky et al. 2011) and habitats for mosquitoes (Claflin and Webb 2017), which may reduce their amenity within urban landscapes. ...
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The SDG14 targets cover more than 70 per cent of the planet, including the coastal zone, where a range of forest resources are located. In this chapter we investigate the potential negative consequences of SDG14 on forest resources, using the example of coastal mangrove forests. SDG14 is likely to have negative impacts on forest resources because it focuses primarily on fisheries, potentially excluding other coastal natural resources. Many SDG14 targets are also more appropriate for oceanic areas, rather than the complex governance arrangements found in the coastal zone. This means that coastal forests such as mangroves may be forgotten, inadvertently impacted or fall through the ‘policy gap’ between terrestrial and marine legislation or between different levels of governance. This also has impacts on the human populations that rely on the ecosystem services provided by mangrove forests, and has implications for environmental justice. To minimise the impacts of SDG14 on mangrove forests and associated coastal communities, we recommend that SDG14 indicators should be broadened to encompass other coastal and oceanic natural resources, decentralisation of coastal zone governance should continue to be encouraged, and management regimes should include coastal communities and enshrine principles of environmental justice.
... Over two thirds of the studies (106, 68%) examined the insurance concepts associated with an increase in extent/quality of an ecosystem, 21 studies (14%) looked at insurance in the context of a decrease in extent/quality, and 18 studies (12%) involved changes to both directions: e.g. the loss and restoration of mangroves (Everard et al., 2014). The remaining studies did not specify, or were not explicitly concerned with, changes per se. ...
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Ecosystems can buffer against adverse events and, by so doing, reduce the costs of risk-bearing to society; benefits which have been termed 'insurance value'. Although the terminology is recent, the concept is older and has its roots in ecological resilience. However, a synthesis of studies through the lens of the insurance value concept is lacking. Here we fill this important knowledge gap by conducting a rapid evidence assessment on how, where and why the insurance value of ecosystems has been measured. The review highlighted the often substantial positive values that were associated with restoration, rehabilitation or avoidance of loss of natural ecosystems. However, many regions, ecosystems and hazards are not widely researched. Most studies focused on forests, agriculture and wetlands, often with an emphasis on habitat restoration to reduce flood risks. Over half the studies provided non-monetary or monetary estimates of value, reporting, for example, improved ecological function, achieved/achievable cost reductions or willingness-to-pay. Nevertheless, the evidence-base remains fragmentary and is characterised by inconsistent reporting of valuation methodologies. This precludes drawing general conclusions. We recommend that future studies of insurance value adopt a common approach to facilitate the development of a more robust evidence-base.
... The critical services and benefits that mangroves provide are broadly recognized [29,30] however, mangroves are also under threat globally [31], and especially so in coastal urban areas where they continue to be cleared for both urban expansion, and infrastructure development, principally port and shipping facilities. In coastal urban areas, maintaining and increasing mangrove cover is understood to be an important component of combating the adverse impacts of climate change for urban populations (see for example [32]), but with the notable exception of recent efforts to steer away from so called grey infrastructure (encompassing engineered structures) and toward green infrastructure for coastal defence [33,34], mangroves are not often identified explicitly as green infrastructure [35]. ...
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Darwin’s mangrove ecosystems, some of the most extensive and biodiverse in the world, are part of the urban fabric in the tropical north of Australia but they are also clearly at risk from the current scale and pace of development. Climate motivated market-based responses, the so-called ‘new-carbon economies’, are one prominent approach to thinking differently about the value of living infrastructure and how it might provide for and improve liveability. In the Australian context, there are recent efforts to promote mangrove ecosystems as blue infrastructure, specifically as blue carbon, but also little recognition or valuation of them as green or urban infrastructure. Drawing on observational and qualitative analysis of semi-structured interviews, this study examines how key stakeholders in Darwin frame and understand mangroves in relation to the urban, and how they are anticipating and responding to governance efforts to frame mangroves and pay for their carbon sequestration and storage services as blue carbon. The push for large infrastructure development and an expanding urban footprint, present serious challenges for mangrove protection, and the study evidences both denial and complacency in this regard. However, although the concept of blue carbon is already taking effect in some circles, it was not viewed as straightforward or as appropriate by all study participants and may very well work in practice to exclude groups within the community. Both clear governance problems, as well as unrecognized and vernacular community connections to mangroves in Darwin, indicate that there are ongoing conceptual and empirical challenges to be considered in recognizing and valuing mangroves as part of urban life.
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Oil spills are a significant stressor to coastal and maritime environments worldwide. The growth responses of Batis maritima and Avicennia germinans seedlings to weathered Deepwater Horizon oiling were assessed through a mesocosm study using a factorial arrangement of 4 soil oiling levels (0 L m⁻², 1 L m⁻², 2 L m⁻², 4 L ⁻m⁻²) × 3 tissue oiling levels (0% of stem height, 50% of stem height, 100% of stem height). Overall, growth metrics of B. maritima displayed much greater sensitivity to both tissue and soil oiling than A. germinans, which exhibited a relatively high tolerance to both routes of oiling exposure. Batis maritima in the 4 L m⁻² soil oiling treatment demonstrated significant reductions in cumulative stem height and leaf number, whereas no significant effects of soil oiling on A. germinans were detected. This was reflected in the end of the study biomass partitioning, where total aboveground and live aboveground biomass were significantly reduced for B. maritima with 4 L m⁻² soil oiling, but no impacts to A. germinans were found. Tissue oiling of 100% did appear to reduce B. maritima stem diameter, but no effect of tissue oiling was discerned on biomass partitioning, suggesting that there were no impacts to integrated growth. These findings suggest that B. maritima would be more severely affected by moderate soil oiling than A. germinans.
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Society is already seeing the ecological and economic benefits from restoration projects. However, the challenge is much bigger than the current efforts from ecologists and economists around the world. The Economics of Restoration is the interdisciplinary research field that is believed to have the necessary tools and instruments to solve this restoration gap, yet a better use and understanding of economic aspects and concepts are still needed. A bibliometric analysis of the field of economics of restoration was done in this study. Bibliometrics can offer insights on the intellectual structure of a discipline and thus indicate future paths for research development. The goal of this study was to identify important and influential economics of restoration research themes and key topics that will strengthen decision-making processes for restoration actions if better addressed in the future. The analysis reveals that few studies go beyond costs, lacking a full estimation of benefits. Economic concepts of uncertainty, public goods and specificity of natural capital are not well incorporated yet, and the relationship between governments and markets, as well as the one between communities and investments, require more attention to scale-up restoration worldwide. This study is believed to be the first one using bibliometrics to guide a discussion around economics of restoration and can be subsequentially replicated in other disciplines.
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Forestry cannot be thought of in isolation from its relations with other sectors and other parts of people’s lives – for both the health of the forests and the well-being of forest peoples. • Forest governance and everyday management are upheld by a superstructure of gendered forest relations – invisible to mainstream forestry – that often disadvantages women as a social group. • Well-intentioned gender programmes can backfire, causing adverse effects on forests and forest peoples, if the efforts are not cognisant of context and power relations. • Constant awareness of differences among various social groups – men, women, different classes, ethnicities – and how their interests intersect differently in various forest contexts is needed for everyone’s energy, creativity and motivation to contribute to sustainable forest management. • Research suggests that greater democratic governance of forests leads to better environmental outcomes. • The gender-neutral framing of some SDG goals undermines efforts towards achieving the outcomes called for in SDG 5.
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Prioritising investments to minimise or mitigate natural hazards such as wildfires and storms is of increasing importance to hazard managers. Prioritisation of this type can be strengthened by considering benefit and cost impacts. To evaluate benefits and costs, managers require an understanding of both the tangible economic benefits and costs of mitigation decisions, and the often intangible values associated with environmental, social and health-related outcomes. We review the state of non-market valuation studies that provide monetary equivalent estimates for the intangible benefits and costs that can be affected by natural hazard events or their mitigation. We discuss whether managers can usefully call upon these available estimates, with a view to using the benefit transfer approach to include non-market values in economic decision frameworks. Additional context-specific non-market valuation studies are required to provide a more accurate selection of value estimates for natural hazard decision making. Decision making would benefit from considering these values explicitly in prioritising natural hazard investments.
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Mangrove forests are one of the world's most threatened tropical ecosystems with global loss exceeding 35% (ref. 1). Juvenile coral reef fish often inhabit mangroves, but the importance of these nurseries to reef fish population dynamics has not been quantified. Indeed, mangroves might be expected to have negligible influence on reef fish communities: juvenile fish can inhabit alternative habitats and fish populations may be regulated by other limiting factors such as larval supply or fishing. Here we show that mangroves are unexpectedly important, serving as an intermediate nursery habitat that may increase the survivorship of young fish. Mangroves in the Caribbean strongly influence the community structure of fish on neighbouring coral reefs. In addition, the biomass of several commercially important species is more than doubled when adult habitat is connected to mangroves. The largest herbivorous fish in the Atlantic, Scarus guacamaia, has a functional dependency on mangroves and has suffered local extinction after mangrove removal. Current rates of mangrove deforestation are likely to have severe deleterious consequences for the ecosystem function, fisheries productivity and resilience of reefs. Conservation efforts should protect connected corridors of mangroves, seagrass beds and coral reefs.
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An earthquake of magnitude 9.0 occurred off the coast of Sumatra on 26 December 2004 at 00:58:50 (UTC)/ 06:28:50 AM (IST). The epicentre of the earthquake was located at 3.29°N and 95.94°E. The focal depth of the earthquake was 30 km. This earthquake generated huge tsunami waves which devastated the Andaman and Nicobar Islands, east coast of India, south Kerala in India and several other countries like Sri Lanka, Indonesia, Thailand and Somalia in the Indian Ocean. The tsunami claimed more than 250,000 human lives in these countries. The aftershocks of this earthquake, numbering more than 250 in the magnitude range 5 ≤ M < 7.3, were located for a length of 1300 km from Sumatra in the south to the Andaman and Nicobar islands in the north, till 30 January 2005. A tsunami run-up survey was conducted immediately after the event to study tsunami damages, inundation areas and to obtain estimates of tsunami heights from perishable evidences like watermarks on houses and ocean debris transported inland. This communication presents results on tsunami heights at different locations along the coastal areas of Tamil Nadu.
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In order to understand the tsunami reduction effect of the coastal permeable structures as the coastal forest and the artificial wave dissipating structure, the hydraulic experiment is carried out. The hydraulic experiment for the tsunami of two different amplitudes with five kinds of models; mangrove, coastal forest, wave dissipating block, rock breakwater, houses, with different structure and porosity was carried out in order to measure an effectiveness in reducing tsunami disaster. Wave height, the horizontal velocity, and wave pressure were measured for each model case. The measuring points are arranged by considering the impact of the tsunami due to the existence of permeable structure, and the change of tsunami at the front and rear side of a model, and the reduction effect by model conditions was compared. Comparing with the forest case and the artificial structure case, the quantity of reduction on the forest case is smaller than the artificial structure. Although there is the reduction effect by the forest existence and the coastal forest is effective in the damage mitigation by tsunami. Experimental results suggest that the tsunami reduction effect in the water level, the flow velocity and fluid force in the structure back by the permeable structures was fully expectable.
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Assessment of tsunami-inflicted damage to island ecosystems assumes great importance owing to the life-sustaining and livelihood support abilities of the ecosystems. Apart from damages caused to life and property, significant damages were caused to ecosystems, which will have long-lasting effects. The tsunami-induced damage to coastal ecosystems was studied in four Nicobar Islands, viz. Camorta, Katchal, Nancowry and Trinkat. The extent of damages assessed ranged from 51 to 100% for mangrove ecosystems, 41 to 100% for coral reef ecosystems and 6.5 to 27% for forest ecosystems. The severity of damages and their consequences suggest the need for a definite restoration ecology programme.
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Describes how mangroves are used for the gathering and/or husbandry of honey. -from Author
Prior to the early 1900s, there were no mangroves in the Hawaiian Archipelago. In 1902, Rhizophora mangle was introduced on the island of Molokai, primarily for the purpose of stabilizing coastal mud flats. This species is now well established in Hawaii, and is found on nearly all of the major islands. At least five other species of mangroves or associated species were introduced to Hawaii in the early 1900s, and while none has thrived to the degree of R. mangle, at least two have established self-maintaining populations (Bruguiera gymnorrhiza and Conocarpus erectus). Mangroves are highly regarded in most parts of the tropics for the ecosystem services they provide, but in Hawaii they also have important negative ecological and economic impacts. Known negative impacts include reduction in habitat quality for endangered waterbirds such as the Hawaiian stilt (Himantopus mexicanus knudseni), colonization of habitats to the detriment of native species (e.g. in anchialine pools), overgrowing native Hawaiian archaeological sites, and causing drainage and aesthetic problems. Positive impacts appear to be fewer, but include uses of local importance, such as harvesting B. gymnorrhiza flowers for lei-making, as well as some ecological services attributed to mangroves elsewhere, such as sediment retention and organic matter export. From a research perspective, possible benefits of the presence of mangroves in Hawaii include an unusual opportunity to evaluate their functional role in coastal ecosystems and the chance to examine unique or rare species interactions.