Growth Performance of Planted Mangroves in the Philippines: Revisiting Forest Management Strategies

Abstract

The effort toward restoring lost mangroves in the Philippines has been commendably immense, specifically during the past two decades. In light of such, it is important to evaluate outcomes and, where appropriate, apply the lessons learned to the current strategies in mangrove forest management. This article synthesizes the results from several research projects assessing the performance of planted mangroves across the country. Overall, there is a widespread tendency to plant mangroves in areas that are not the natural habitat of mangroves, converting mudflats, sandflats, and seagrass meadows into often monospecific Rhizophora mangrove forests. In these nonmangrove areas, the Rhizophora seedlings experienced high mortality. Of the few that survived (often through persistent and redundant replanting), the young Rhizophora individuals planted in these nonmangrove and often low intertidal zones had dismally stunted growth relative to the corresponding growth performance of individuals thriving at the high intertidal position and natural mangrove sites. From this evidence, this article argues that a more rational focus of the restoration effort should be the replanting of mangroves in the brackish-water aquaculture pond environments, the original habitat of mangroves. For such, a number of management options can be explored, the implementation of which will ultimately depend on the political will of local and national governments.

Full text

Article Maricar S. Samson and Rene N. Rollon
Growth Performance of Planted Mangroves
in the Philippines: Revisiting Forest
Management Strategies
The effort toward restoring lost mangroves in the
Philippines has been commendably immense, specifically
during the past two decades. In light of such, it is
important to evaluate outcomes and, where appropriate,
apply the lessons learned to the current strategies in
mangrove forest management. This article synthesizes
the results from several research projects assessing the
performance of planted mangroves across the country.
Overall, there is a widespread tendency to plant man-
groves in areas that are not the natural habitat of
mangroves, converting mudflats, sandflats, and seagrass
meadows into often monospecific Rhizophora mangrove
forests. In these nonmangrove areas, the Rhizophora
seedlings experienced high mortality. Of the few that
survived (often through persistent and redundant replant-
ing), the young Rhizophora individuals planted in these
nonmangrove and often low intertidal zones had dismally
stunted growth relative to the corresponding growth
performance of individuals thriving at the high intertidal
position and natural mangrove sites. From this evidence,
this article argues that a more rational focus of the
restoration effort should be the replanting of mangroves
in the brackish-water aquaculture pond environments, the
original habitat of mangroves. For such, a number of
management options can be explored, the implementa-
tion of which will ultimately depend on the political will of
local and national governments.
INTRODUCTION
During the past three quarters of the century, the deforestation
of Philippine mangroves has been massive (1–8). Some 337 000
hectares (75%) of mangrove habitats have been lost, the bulk
(278 657 ha; 66%) of which occurred between 1950–1990 (2, 3).
Such forest loss has been largely attributed to its conversion
into brackish-water fishponds (230 000 ha; ;60%) (2), as well as
timber harvesting for building materials, firewood, charcoal,
and coastal development. Realizing this immense decline in
mangrove habitats, several mitigating efforts were implemented,
the earliest (e.g., in Bais Bay in the 1930s and Banacon, Bohol,
in the 1950s; 2–4; Table 1) of which were intended primarily for
wood supply and coastal protection against winds and typhoons
(2–4). However, these and most subsequent actions have been
mainly vast afforestation (i.e., establishing mangroves on areas
not previously forested) (4–7), although some of the more ideal
reforestation and enhancement of existing forests can be
mentioned (e.g., 8, 9).
During the past 2 decades, more than 44 000 hectares (10)
(see also Table 1), mostly nonmangrove mudflats, sandflats,
and seagrass beds had been planted with mangroves, using
almost exclusively the genus Rhizophora (4–7, 11, 12). Relative
to other mangrove genera, the large and long propagules of
Rhizophora can be handled much more conveniently and may
not require nursery culture before planting in frequently flooded
(i.e., mid to low intertidal) areas. The estimated cost of such
planting effort is at least PhP 880 million (USD 17.6 million),
assuming a conservative cost estimate of PhP 20 000 (USD 400)
per hectare (17) using 440 million Rhizophora propagules at a
planting density of 1 per square meter (18). Given this seemingly
immense effort, it is important to evaluate the outcomes and,
where appropriate, apply what we learn to ongoing forest
management (10).
In this study, we synthesize the findings of a number of
research projects (11, 12, 16, 19–21), aimed at assessing a
number of mangrove forest management locations in the
Philippines (Pangasinan, Calauag and Tayabas Bays, Palawan,
Bohol, Surigao, and Tawi-Tawi; Fig. 1) several years after the
initiation of such efforts. Aside from determining mangrove
community structure in these areas using the transect-plot
method (i.e., species composition, stem density, size class,
height, crown, etc.) (22), we focus our observations on those
factors affecting the survival and growth performance of
developing trees. More specifically, we assessed the differences
in the vertical growth of young Rhizophora (the most commonly
Figure 1. Mangrove locations surveyed () in a number of intensive
field campaigns, covering .70 sites across the Philippines. These
areas, particularly Tayabas and Calauag Bays, Palawan and Bohol,
are among those where considerable amounts of mangrove forests
still exist and where substantial planting efforts had been carried out.
234 Ambio Vol. 37, No. 4, June 2008ÓRoyal Swedish Academy of Sciences 2008
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planted genus) at these sites, comparing, as much as possible,
natural, reforested, and afforested vegetations. Vertical growth
was derived by applying mainly age-reconstruction techniques
(23, 24), corrected appropriately for plastochron intervals
determined at selected sites (25).
PLANTING RHIZOPHORA IN NONMANGROVE AREAS
In the Philippines, the operations of brackish-water fishponds
are governed by foreshore lease agreements ([FLAs] 25-year
duration and renewable) between the operators and the state.
Such FLAs helped facilitate the massive mangrove forest
clearing in the mid- to late-1900s, although now such clearing
for fishponds is completely outlawed (26). Ideally, mangrove
reforestation should take back some of the 230 000 hectares of
cleared mangrove areas. In recent years, the pressure from
various sectors (nongovernmental organizations, scientific
community, etc.) to revert some of the idle and/or abandoned
aquaculture ponds into mangrove forests again has been
mounting, but the legal process and mechanics to realize such
advocacy have been extremely difficult until now (e.g., 27).
Virtually no FLA certificate holders are willing to yield some of
these areas for revegetation. Most want to hold on to their
active FLAs and have those expiring and/or expired certificates
renewed. Meanwhile, the clamor and financial support from
both national and international sources for various mangrove
restoration projects is increasing. As a consequence, the
planting of mangroves has become a standard practice in
coastal resource management (CRM) in recent years. The
design and implementation of CRM plans often involves
lengthy consultation, planning, and political consensus building
on which certain zones of the coastal environment are
delineated for mangrove planting. Typically, these zones were
located in areas least likely to conflict with existing resource
uses and interests (i.e., available intertidal sandflats mudflats,
and/or seagrass beds) instead of the more desirable aquaculture
ponds. Furthermore, the handy, large, and long propagules of
Rhizophora were widely used as planting materials irrespective
of where these zones were positioned in relation to the range
where Rhizophora occurs in a natural zonation of mangroves (4,
6, 16).
Although this may seem sound from the perspective of
coastal management, the practice has two major ecological
problems: i) mangrove species-site incompatibility and ii) the
conversion of other habitats (particularly mudflat, sandflats,
and seagrass beds) into mono-specific Rhizophora plantations.
These mudflat, sandflats, and seagrass beds are usually located
at seafronts (and thus exposed to stronger mechanical wind
stress and wave action) and are frequently within the low
intertidal zone. Rhizophora species are broad-leafed and occur
naturally in the mid-forest, middle intertidal zone, so being
planted at the seafronts may pose serious survival problems (28,
29). Wind and wave stress damage planted seedlings directly
and carry debris (macroalgae, trash, logs; Fig. 2b,e). In many
cases, the anchoring architecture of young Rhizophora (in
contrast to those of Sonneratia and/or Avicennia occurring more
commonly at the seafronts) cannot withstand the eroding power
of direct wave action (Fig. 2d, h). In cases where such
plantations are already at the low intertidal zone, drowning of
the seedlings may occur during periods of the year when the
mean tide level is high and young plants are submerged over an
extended period (Fig. 2a) (see also 30, 31). Adding to this stress
of prolonged immersion, the stems of seedlings have also been
found to serve as desirable substrates for colonizing oysters and
barnacles (Fig. 2f), hastening the mass mortalities of Rhizo-
phora seedlings in some sites (16, pers. obs.).
Even granting that some mangroves planted in these
apparently inappropriate environments survive and flourish
(e.g., NE Bohol mangrove plantations), the habitat gains may
be offset by the corresponding loss of mudflats and sandflats
(which, at low and high tides, may be used as feeding grounds
for shorebirds and some species of fish, respectively) and
productive seagrass meadows may just offset whatever modest
gains we may have in converting these zones into mangrove
habitats (see also 7).
Table 1. Some of the better-documented mangrove management initiatives in the Philippines over several decades now. Several other similar
initiatives elsewhere (e.g., Calauag, Sorsogon, Samar, Eastern Mindanao, etc.) had not been formally reported in accessible forms.
Location Area (ha) Year Notes
Daco Is., Bais, Negros Oriental 1930s–1940s Backyard planting (4, 6)
Bais Bay, Negros Oriental 1940s–1950s ‘‘Hacienda’’ (along edges) planting (3, 4, 6)
Banacon Is., Jetafe, Bohol 400 1957–1958, 1964–1970 Community participation; included harvesting and
selling of propagules, partial thinning operations for
firewood, charcoal, piles, posts, and deployment of
fish aggregating device within mangrove forests
(3, 4, 6, 13)
Pagangan Is., Calape, Bohol along a 4.8 km causeway 1968 School initiated (3)
Marungas, Sulu 150 1981 First large-scale government-initiated project (3)
Basilan, Sulu 50 1985 Bureau of Forestry Development (3)
5 sites in Bohol, Cebu, Negros Oriental 650 1984 Central Visayas Regional Project; World Bank-funded,
USD 3.5 million; stewardship contracts (3)
Negros Oriental 14 As of 1986 Community-based (57 planters, two towns) (3)
Cebu 365 As of 1986 Community-based (384 planters, five towns) (3)
Bohol 562 As of 1986 Community-based (870 planters, 10 towns) (3)
Hunan, Buenavista, Bohol 4 1990–1995 Aquasilvipasture in an abandoned fishpond (13)
Catanauan, Quezon 0.8 — Aquasilviculture (13)
11 regions under the Fisheries
Resource Management Project
;1900 As of 2003 Project implemented by the Department of
Agriculture–Bureau of Fisheries and Aquatic
Resources with loan funding from Asian
Development Bank and Japan Bank for International
Cooperation (15)
Lucena City, Quezon 160 000 propagules planted As of 2005 Local government unit (LGU) initiated project (16)
Pagbilao, Quezon 35 As of 2005 Partnership of LGU and Mirant–Pagbilao (16)
Unisan, Quezon 2 As of 2005 LGU-initiated (16)
Macalelon, Quezon 10 As of 2005 LGU-initiated (16)
Catanauan, Quezon 20 As of 2005 LGU-initiated (16)
Mulanay, Quezon 2 As of 2005 LGU-initiated (16)
Main sources: Primavera (3), Melana et al. (13, 14), Roldan (15), and MERF (11).
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GROWTH PERFORMANCE OF THE SURVIVING
TREES
Although the stem density and canopy cover of reforested and/
or afforested mangroves did not significantly differ from those
of existing natural stands (Table 2), these mainly afforestation
efforts (if able to overcome high seedling mortalities through
redundancies [18] and persistent replanting [pers. obs.])
drastically altered the natural species assemblage pattern,
transforming the Avicennia–Sonneratia dominated seafronts
into monospecific Rhizophora zones (Fig. 3). Inferring from
the growth patterns of young individuals, the surviving
Rhizophora trees at the seafronts performed dismally relative
to their counterparts at the high intertidal zones. For example,
the internodal lengths along the main stem of Rhizophora
surviving in the coarse, sandy, low intertidal zone in NE Bohol
were ,5 cm during 12 years of existence (1992–2004) and were
,3 cm during the initial 10-y period (Fig. 4). This was in strong
contrast to the growth performance of the same species growing
in the corresponding high intertidal area, showing much longer
internodes (average length: ca. 10 cm) and reflecting much
clearer seasonal and interannual variability (range: 3–14 cm).
One internode is equivalent to a vertical elongation over about
40 days (23–25, 32). In a broader perspective, such poorer
growth performance of young Rhizophora at the seafronts in
NE Bohol (Fig. 4) was also shown clearly in all of the other
mangrove study areas across the country (Fig. 5), demonstrat-
ing that Rhizophora individuals surviving at the low intertidal
zone (seafronts) would barely attain 3 m in height during the
first 10 years, whereas the corresponding vertical growth of
Rhizophora trees at the high intertidal zone would be 2–3 times
as much.
Furthermore, the prop-root architecture of Rhizophora trees
at the seafront, although also able to trap sediments, would be
likely less efficient in maintaining sediment elevation as
compared with the complex pneumatophore system of the
Figure 2. Some examples of the less successful mangrove enhancement initiatives in the Philippines, mainly planting Rhizophora at the
seafronts: (a) under a prolonged period of immersion, Rhizophora seedlings planted at the lower intertidal zone may ‘‘drown,’’ causing
massive mortalities in Tayabas Bay (16, pers. obs.); (b and e) macroalgae and other debris may cause defoliation of the broad-leafed
Rhizophora; (c and g) planting between pneumatophores (c) of Sonneratia and aided by bamboo stakes (g) did not prevent many Rhizophora
seedlings from dying (g; i.e., ,50 of the ;1000 seedlings planted survived; Agdangan, Quezon); (d and h) part of 10-ha mangrove plantation
(carbon-sink) effort in which Rhizophora seedlings mostly (i.e., .95%of the seedlings within sampling plots) died after only about 9 months,
apparently because of the mechanical stress of wave action and substrate erosion; and (f) seedling stems serving as substrates for oyster
colonization.
Table 2. Canopy index (i.e., total crown area relative to the area of substrate surveyed) and stem density (i.e., number of trees per 100 m
2
)of
various mangrove forest types (natural, reforested, and afforested) across different locations in the Philippines. Reforested and afforested
types were mostly situated at the low intertidal positions. Numbers in parenthesis indicate the number of sites sampled within locations
(Fig. 1). Error terms are standard deviations.
Location Parameter Natural Reforested Afforested Overall
Calauag Canopy 2.432 62.275 (5) 2.785 61.431 (10) 3.220 62.616 (2) 2.732 61.713 (17)
Stem density 30.2 618.2 (5) 40.7 615.2 (10) 43.0 619.8 (2) 37.9 616.3 (17)
Tayabas Canopy 3.506 63.098 (22) 3.288 61.155 (5) — 3.465 62.822 (27)
Stem density 42.0 626.3 (22) 67.2 639.8 (6) 100.0 60.0 (3) 52.5 633.1 (31)
Palawan Canopy 2.384 61.389 (10) 4.950 60.000 (1) 1.570 60.919 (2) 2.456 61.473 (13)
Stem density 21.7 614.6 (10) 36.0 60.0 (1) 66.5 641.7 (2) 29.7 624.2 (13)
Bohol Canopy 2.215 61.435 (2) 1.410 60.000 (1) 2.270 60.000 (1) 1.129 61.029 (7)
Stem density 26.0 69.9 (2) 27.0 60.0 (1) 92.5 660.8 (4) 64.1 655.8 (7)
Surigao Canopy 3.925 61.096 (2) — 2.270 60.000 (1) 3.373 61.230 (3)
Stem density 53.5 629.0 (2) — 55.0 60.0 (1) 54.0 620.5 (3)
Tawi—Tawi Canopy 1.286 60.191 (2) 1.640 60.000 (1) — 1.403 60.245 (3)
Stem density 30.0 622.6 (2) 16.0 60.0 (1) — 25.3 617.9 (3)
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naturally-seafront taxa Avicennia and/or Sonneratia (33, 34). If
one of the objectives of mangrove forest enhancement is the
mitigation of upland-derived sedimentation on more seaward
habitats (e.g., seagrass beds and coral communities), such
sediment trapping and retention capacity of various mangrove
species should be seriously considered as well.
ACTION POINT: REVISIT CURRENT PRACTICES AND
REVERT SOME AQUACULTURE PONDS INTO
MANGROVE FORESTS
The circumstances (ecological, socio-institutional, and econom-
ic; see also Table 3) surrounding the management of a particular
coastal area can be very complex. However, the widespread
practice of converting the ‘‘available’’ mudflats, sandflats, and
seagrass beds into often monospecific Rhizophora forests should
be reconsidered. Such expensive and labor-intensive efforts
offer little ecological gains. It would be far more appropriate to
reforest some of the former (natural) mangrove areas, which are
Figure 3. Afforesting the seafront: tree density, basal area, and canopy cover of mangrove trees in Lagay (Calauag), traversing across an
intertidal regime (i.e., high, mid, and low intertidal; xrange indicates elevation relative to the mean low tide level [zero datum]). Values for
different tree classes (DBH range) are also shown.
Figure 4. Temporal variation in the length of internodes along the
main stem of young planted Rhizophora apiculata growing in
Cataban (coarse sand, low intertidal zone) and San Francisco
(muddy, high intertidal zone) in Talibon NE Bohol. For clarity, error
bars were omitted.
Figure 5. Estimated mean annual rates of vertical growth (i.e.,
internodal increments along the main stem) of young Rhizophora
spp. trees growing in different intertidal regime (i.e, high, mid, and
low intertidal zones) in six mangrove locations in the Philippines,
with various number of sites per location. Numbers in parentheses
inside bars indicate the total number of young mostly-planted trees
sampled corresponding to the tidal regime. Different letters attached
to bars indicate significant differences (p ,0.05; Tukey test) across
tidal regime within sites.
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currently utilized as brackish-water fishponds. The legal,
institutional, and economic challenges of doing so are
overwhelming. The issue of food security also merits consider-
ation. By producing fish and fishery products through
aquaculture rather than harvesting from overexploited wild
stocks, an important protein source for the booming human
population is provided. But as has long been argued, a balance
between aquaculture food production and the conservation of
mangrove habitats must be achieved given the many and diverse
values offered by mangroves, including diverse seafood, wood
products, storm protection, etc. (4, 8, 9, 36–38). Often, when
taken together, such values may far exceed the benefit of
producing fish in the ponds.
Preliminary Questions
In the Philippine context, determining the management options
for idle and active brackish-water aquaculture ponds might be
pursued by first addressing some prejudicial questions on
whether i) the ponds are covered with existing and valid FLAs;
ii) the fish production from these ponds would be necessary in a
broader fisheries perspective, perhaps as evaluated using
bioeconomic analysis tools that compare costs and benefits of
various management actions (e.g., Grasso [39] and other
broader-scale models [40–42]); iii) these ponds are operating
at optimal levels (e.g., various systems of prawn culture [1]), and
iv) these ponds, if indeed reverted, could be revegetated by
natural recruitment of mangrove propagules. Depending on the
answers to these questions, a decision tree might be constructed
(Fig. 6), leading to a number of management options.
Management Options
Option 1. For ponds with valid FLAs and optimal
operation, the only option would be to leave those ponds as
they are now. These legal rights make questions 2 and 4
irrelevant.
Option 2. For ponds with valid FLAs but operating at a
suboptimal level, measures to increase fish yield per unit pond
area should be pursued (for instance, see Primavera [1]). By
doing so, some portions of the existing pond area may no longer
be necessary. For such excess area, FLA holders should then be
encouraged to terminate the FLA covering the portion of the
existing ponds, and revegetation must be pursued following
either Option 4 or 5. To make this option more amenable to
FLA holders, economic incentives (e.g., tax holidays, ecolabel-
ing, technical support to optimizing operation, disease control,
etc. [43]) may be explored.
Option 3. For ponds without valid FLAs (i.e., terminated,
expired, or otherwise illegal ever since), question 2 should be
asked to evaluate whether retaining the use of the area (either in
its entirety or just some part thereof) as aquaculture ponds
would still be desirable. If that is the case, an FLA may be
sought. Among others, the bioeconomic analysis (39–42) may
consider the supply (including wild stocks) and demand of fish
in both a local and a much broader fisheries perspective.
Option 4. For ponds without valid FLAs and where existing
conditions (mainly physico-chemical characteristics and the
dispersal possibilities of propagules from nearby areas) permit
natural revegetation, the pond dikes may be removed. The
resulting reinstallation of the natural tidal flooding regime
should permit natural recolonization of mangroves (see also 7).
Option 5. In many cases, aquaculture operations will have
significantly altered the sediment conditions of sites. The
possibility of natural colonization may be low as well in cases
where nearby mangroves have been cleared or highly fragment-
ed. Taking site-specific conditions into account, a full-scale
restoration may then proceed carefully, with consideration of
the suitability of species and the principles of community
succession.
Indeed, focusing our effort on reverting brackish-water
ponds into mangrove forests again will yield much more
substantial results. To illustrate, there are 230 and 480 hectares
Table 3. Ecological, social/institutional, and economic circumstances surrounding mangrove management initiatives in the Philippines.
Ecological Social/ institutional Economic
Lack of baseline ecological assessment of the
target areas prior to mangrove rehabilitation (11)
Site and species unsuitability (11, 13)
Monospecific forest (Rhizophora spp.) (11)
Poor growth performance (11)
Infestations by barnacles and other pests (11, 13)
Natural calamities (11, 13)
Domestic and agricultural pollution (13)
Animal grazing (11, 13)
Sand accretion (11)
Lack of clearly defined goals
of mangrove management (10)
Lack of sustainability mechanisms such as
monitoring and evaluation system,
maintenance, and financing support (11)
Aquaculture as a development strategy (3)
Lack of coordination among concerned
agencies (3)
Weak law enforcement, especially on the
moratorium on fishpond development and
cutting of mangroves (3)
Lack of interest by the local community (13)
Conflicting interests of various users (3)
Reforestation contracts benefited only
a few (13)
Food security
Low perceived economic values of mangrove
habitats and hence aquaculture development was
favored (3)
Lack of funding for sustainability of projects (11)
Long waiting time for economic returns (3)
Mismanagement of funds (3)
Figure 6. A possible decision-tree of options for idle and active
brackish-water fishponds in the Philippines: (1) Status quo; (2)
Optimize fish yield and reduce pond size as small as possible; (3) If
pond existence is necessary based on a bioeconomic analysis,
reapply for FLA; go to Question 3; (4) Restore the natural tidal
flooding regime by removing pond dikes to enable natural
revegetation, and (5) Determine physico-chemical conditions, may
need to restore substrate elevation (7, 41), study species appropri-
ateness, reforest applying species suitability and community
succession principles.
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of idle and active aquaculture ponds, respectively, in Calauag
(44). Revegetating most of these existing idle ponds (see also 7,
45) will have far greater impact than converting a number of
inappropriate sites (i.e., 1–2 hectares of sandflats, mudflats, and
seagrass beds) as commonly practiced over the last decade. This
will increase the present mangrove cover (930 ha [44]) by 25%.A
parallel argument could be put forward for Tayabas Bay, which
lost about 70%of its historical mangrove cover (Table 4) to
mostly aquaculture development.
Other essential pursuits: lessons learned from field
observations. Synthesizing the findings from our research
activities (11, 12, 19–21), management efforts need not be
limited to revegetating former mangrove areas and/or creating
new mangrove plantations. Enhancing the productivity of
existing degraded and fragmented forests should also be
pursued by filling-in forest openings. It may be desirable to
pursue mangrove planting along the seaward edge because of
competing land uses. In such case, it would be better if
pneumatophore-producing taxa and those better adapted to
seafront conditions (e.g., Avicennia,Sonneratia, etc.) were
planted before other species. With the pneumatophores,
sediment trapping and substrate conditions modification are
facilitated, which may enhance natural recruitment by trapping
more mangrove propagules. To increase the success rate in such
areas, seedlings should be protected against strong waves,
wastes, and debris (e.g. stakes, fence, protective nets, etc.). In
any case, mangrove nurseries may need to be established.
To further increase the collaboration of local communities,
the current honorarium-based incentive system might be
strengthened by, for example, i) granting permits and licenses
for aquasilviculture; ii) enhancing a market system for
permissible harvests (i.e., oysters, crabs); and iii) granting
tenurial instruments (i.e., community based forest management
agreement) (see also 4, 5). In an increasing number of successful
cases, ecotourism in mangrove areas (i.e., bird watching and
other nature-appreciation board walks with local guides) has
brought a supplemental livelihood to the local community and
thus may be pursued. Excellent models (also the more ideal
reforestation efforts) would include the Pagbilao Mangrove
Demonstration Site (Tayabas Bay), the Pangasinan Mangrove
Reserve (Bani, Pangasinan), Buswang Mangroves (Aklan), and
the Talabong Mangrove Forest Reserve (Bais Bay, Negros
Oriental).
Finally, the stronger role of the local government units
(LGUs) in coordination with the Department of Environment
and Natural Resources and the Bureau of Fisheries and Natural
Resources is crucial in the design, implementation, monitoring,
and evaluation of any mangrove enhancement project. Of
critical importance is the stronger involvement of the LGUs in
defining clearly the goals (coastal protection, fisheries and
productivity, ecotourism, etc.) and thus also formulating the
indicators of success. In making the role of LGUs stronger, the
sustainability of these efforts would be, to a large extent,
enhanced through appropriate local legislations, competent
management bodies, and corresponding local budget alloca-
tions rather than relying as they have on initiatives driven from
the national and international levels.
CONCLUSIONS
The massive deforestation of Philippine mangroves over the
past three quarters of the century has, in recent years, prompted
various efforts to increase mangrove coverage. These efforts
have mainly included afforestation of Rhizophora spp., con-
verting mudflats, sandflats, and seagrass meadows into often
monospecific mangrove forests, making the ecological gains of
such efforts highly uncertain. Worse, in these nonmangrove
areas, seedlings experienced high levels of mortality and, in the
few that survived (apparently through stubborn, expensive
replanting), have displayed dismally stunted growth relative to
the corresponding growth performance of individuals thriving
at the high intertidal position and natural mangrove sites.
Our evidence suggests that the current practices and
strategies on mangrove forest management in the Philippines
need to be reviewed. This article stresses that a more rational
focus of such efforts should be on the recovery of some of the
former mangrove areas that were lost to brackish-water
aquaculture. A number of prejudicial questions could be
evaluated that may lead us to constructing a decision tree and
hence aid in identifying a number of highly workable options.
In the end, however, implementation of these options may
depend on the political will of local and national governments.
References and Notes
1. Primavera, J.H. 1991. Intensive prawn farming in the Philippines: ecological, social, and
economic implications. Ambio. 20, 28–33.
2. Primavera, J.H. 1995. Mangroves and brackishwater pond culture in the Philippines.
Hydrobiologia 295, 303–309.
3. Primavera, J.H. 2000. Deve lopment and conservation of Phil ippine mangroves:
institutional issues. Ecol. Econ. 35, 91–106.
4. Walters, B.B. 2004. Local management of mangrove forests in the Philippines: successful
conservation or efficient resource exploitation? Hum. Ecol. 32, 177–193.
5. Primavera, J.H., Sadaba, R.B., Lebata, M.J.H.L. and Altamirano, J.P. 2004. Handbook
of Mangroves in the Philippines–Panay. SEAFDEC Aquaculture Department, Iloilo,
Philippines, 106 pp.
6. Walters, B.B. 2000. Local mangrove planting in the Philippines: are fisherfolk and
fishpond owners effective restorationists? Restor. Ecol. 8, 237–246.
7. Lewis, R.R. 2005. Ecological engineering for successful management and restoration of
mangrove forests. Ecol. Eng. 24, 403–418.
Table 4. Estimated extent of mangrove areas in Tayabas Bay; historical potential (derived from topographic maps from National Mapping and
Resources Information Authority) and 2000 satellite image (classified to distinguish mangrove areas).
Town/city
Extent of mangrove area, hectares
Historical potential %of total 2000 satellite image %of total Forest loss %reduction
Lucena 830.11 14.15 190.32 10.58 639.79 77.07
Sariaya 276.13 4.71 85.60* 4.76 190.53 69.00
Pagbilao 1222.59 20.83 549.33 30.54 673.26 55.07
Padre Burgos 782.95 13.34 287.56 15.99 495.39 63.27
Agdangan 157.62 2.69 52.79 2.93 104.83 66.51
Unisan 365.55 6.23 186.58 10.37 178.97 47.67
Pitogo 554.46 9.45 69.02 3.84 485.44 87.55
Gumaca 57.04 0.97 17.68* 0.98 39.36 69.00
Macalelon 389.04 6.63 73.39 4.08 315.65 81.14
General Luna 281.24 4.79 30.80 1.71 250.44 89.05
Catanauan 527.25 8.99 101.65 5.65 425.60 80.72
Mulanay 88.52 1.51 51.90 2.89 36.62 41.37
San Francisco 335.59 5.72 102.26 5.68 233.33 69.53
Total for Tayabas Bay 5868.09 1798.88 4069.21 69.53
*Absent in classified image, assumed 69%loss (average for all sites).
Ambio Vol. 37, No. 4, June 2008 239ÓRoyal Swedish Academy of Sciences 2008
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8. Walters, B.B. 2003. People and mangroves in the Philippines: fifty years of coastal
environmental change. Environ. Conservat. 30, 293–303.
9. Walton, M.E.M., Samonte-Tan, G.P.B., Primavera, J.H., Edwards-Jones, G. and Vay,
L.L. 2006. Are mangroves worth replanting? The direct economic benefits of a
community-based reforestation project. Environ. Conservat. 33, 335–343.
10. Field, C.D. 1998. Rehabilitation of mangrove ecosystems: an overview. Mar. Pollut.
Bull. 37, 383–392.
11. Postresource and social assessment monitoring of Calauag and Tayabas Bays, through
the Marine Environment Resources Foundation (MERF), Inc., of the Marine Science
Institute, University of the Philippines, with support from the Bureau of Fisheries and
Aquatic Resources (BFAR)–Fisheries Resource Management Program (FRMP), 2005–
2006.
12. Baseline assessment of mangroves and seagrasses in NE Bohol, Tawi-Tawi, Surigao del
Sur and northern Palawan, with funding from USAID through Ecogov (Philippine
Ecogovernance Project)-MERF, 2003–2004.
13. Melana, D.M., Melana, E.E. and Mapalo, A.M. 2000. Mangrove Management and
Development in the Philippines. Oral presentation at Mangrove and Aquaculture
management, 14–16 February, 2000, Kasetsart University Campus, Bangkok, Thailand.
14. Melana, D.M., Atchue, J. III, Yao, C.E., Edwards, R., Melana, E.E. and Gonzales, H.I.
2000. Mangrove Management Handbook. Department of Environment and Natural
Resources, Manila, Philippines through the Coastal Resource Management Project,
Cebu City, Philippines, 96 pp.
15. Roldan, R.G. 2004. An Assessment of Fish Sanctuary and Mangrove Rehabilitation
Projects Established Under the Fisheries Resource Management Project. FRMP Technical
Monograph Series No. 9. Ablaza, E.C. (ed). FRMP, 20 pp.
16. As part of the activities of these research projects (11, 12, 19–21), a series of consultation
meetings, focus group discussions, conferences, and workshops were carried out to
gather information, particularly those which could not be obtained from existing
literature.
17. Roughly, the further breakdown would include: PhP 5000 (USD 100) for propagules;
PhP 10 000 (USD 200) for labor; PhP 3500 (USD 70) for transportation, and PhP 1500
(USD 30) for fence and other materials. This estimate does not include expenses for
redundancies (18), subsequent monitoring, maintenance, and/or replanting activities.
18. A spacing of 1 m apart between seedlings has been recommended by the Department of
Environment and Natural Resources (DENR), Philippines (14). This spacing
recommendation has been strictly followed across the country, although in many cases
(11, 12, 19–21), 2–5 seedlings were planted together on the same spot at the same time
(redundancy), apparently hoping that at least 1 would survive.
19. A study on the accumulated sediment loading in Bolinao, Anda, Bani, and Alaminos
(Pangasinan) under the SAGIP-Lingayen Project, 2005–2006.
20. Assessment of the possible impact of the hydrometallurgical processing plant project of
the Rio Tuba mining on the marine habitats (Coral Bay, Bataraza, Palawan), February–
March 2006.
21. Monitoring of the coastal resources of northern Palawan (PATH 2004).
22. English, S., Wilkinson, C. and Baker, V. 1994. Survey Manual for Tropical Marine
Resources. ASEAN-Australia Marine Science Project, Australian Institute of Marine
Science, 368 p.
23. Duarte, C.M, Thampanya, U., Terrados, J., Geertz-Hansen, O. and Fortes, M.D. 1999.
The determination of the age and growth of SE Asian mangrove seedlings from
internodal counts. Mangroves and Salt Marshes 3, 251–257.
24. Coultier, S.C., Duarte, C.M., Tuan, M.S., Tri, N.H., Ha, H.T., Giang, L.H. and Hong,
P.N. 2001. Retrospective estimates of net leaf production in Kandelia candel mangrove
forests. Mar. Ecol. Prog. Ser. 221, 117–124.
25. In a number of sites in Calauag and Tayabas Bays, we tagged Rhizophora spp.
individuals to determine the plastochron interval (PI). For each of the sites, we counted
the number of leaf-pairs produced by each of the 100–150 tagged trees during a period of
1–2 months. The plastochron intervals were then calculated (see also 23–24). Our results
were comparable to those obtained from an earlier study on Rhizophora spp. trees
elsewhere (Pangasinan), reflecting values of PI ca. 40 days (26). Doing such study in four
quarters of the year 2001, Salmo (26) did not find significant differences across these
quarters.
26. Republic Act No. 8550. An act providing for the development, management, and
conservation of the fisheries and aquatic resources, integrating all laws pertinent thereto,
and for other purposes. Otherwise known as ‘‘The Philippine Fisheries Code of 1998,’’
signed into Law, 25 February 1998.
27. Hibionada, F.F. 2007. The heroes in Kai and Paz: remembering the man who brought
‘‘Fish for the People’’ and honoring the works of his Ilongga-scientist wife. The News
Today, 14 March 2007. (see also http://www.thenewstoday.info/2007/03/14/index.html)
28. Padilla, C., Fortes, M.D., Duarte, C.M., Terrados, J. and Kamp-Nielsen, L. 2004.
Recruitment, mortality and growth of mangrove (Rhizophora sp.) seedlings in Ulugan
Bay, Palawan, Philippines. Trees–Structure and Function 18, 589–595.
29. Thampanya, U., Vermaat, J.E. and Duarte, C.M. 2002. Colonization success of
common Thai mangrove species as a function of shelter from water movement. Mar.
Ecol. Prog. Ser. 237, 111–120.
30. Kitaya, Y., Sumiyoshi, M., Kawabata, Y. and Monji, N. 2002. Effect of emergence and
shading of hypocotyls on leaf conductance in young seedlings of the mangrove
Rhizophora stylosa.Trees—Structure and Function 16, 147–149.
31. Kitaya, Y., Jintana, V., Piriyayotha, S., Jaijing, D., Yabuki, K., Izutani, S., Nishimiya,
A. and Iwasaki, M. 2002. Early growth of seven mangrove species planted at different
elevations in a Thai estuary. Trees Structure and Function 16, 150–154.
32. Salmo, S.G. 2002. Responses of Rhizophora Mucronata (Lamarck) Seedlings to Spilled
Oil. MS Thesis, Institute of Environmental Science and Meteorology, College of Science,
University of the Philippines, Diliman, Quezon City, 95 pp.
33. Krauss, K.W., Allen, J.A. and Cahoon, D.R.. 2003. Differential rates of vertical
accretion and elevation change among aerial root types in Micronesian mangrove
forests. Estuar. Coast. Shelf Sci. 56, 251–259.
34. In connection with a project on sediment loading (19), the sediment accumulated around
Avicennia marina trees was determined. The effective area (typically 10 m 310 m) was
subdivided into 1-m grids. In each of these grids, the sediment elevation was measured
using a hose water level technique. A contour map was then generated from the elevation
matrix and the volume above a base grid surface (accumulation) was computed (Surfer
version 7 software), yielding a rate of accumulation of ca. 10.5 kg m
2
y
1
, closely similar
to earlier estimates elsewhere (Walsh and Nittrouer [35]: 1.1 g cm
2
y
1
or 11 kg m
2
y
1
).
35. Walsh, J.P. and Nittrouer, C.A. 2004. Mangrove-bank sedimentation in a mesotidal
environment with large sediment supply, Gulf of Papua. Mar. Geol. 208, 225–248.
36. Walters, B.B. 2005. Patterns of local wood use and cutting of Philippine mangrove
forests. Econ. Bot. 59, 66–76.
37. Ro
¨nnba
¨ck, P. 1999. The ecological basis for economic value of seafood production
supported by mangrove ecosystems. Ecol. Econ. 29, 235–252.
38. Barbier, E.B. 2000. Valuing the environment as input: review of applications to
mangrove fishery linkages. Ecol. Econ. 35, 47–61.
39. Grasso, M. 1998. Ecological-economic model for optimal mangrove trade off between
forestry and fishery production: comparing a dynamic optimization and a simulation
model. Ecol. Model. 112, 131–150.
40. Manson, F.J., Loneragan, N.R., Harch, B.D., Skilleter, G.A. and Williams, L. 2005. A
broad-scale analysis of links between coastal fisheries production and mangrove extent:
a case-study for northeastern Australia. Fish. Res. 74, 69–85.
41. Wolff, M., Koch, V. and Isaac, V. 2000. A trophic flow model of the Caete
´mangrove
estuary (North Brazil) with considerations for the sustainable use of its resources.
Estuar. Coast. Shelf Sci. 50, 789–803.
42. Licuanan, W.Y., Alin
˜o, P.M., Campos, W.L., Castillo, G.B. and Juinio-Men
˜ez, M.A.
2006. A decision support model for determining sizes of marine protected areas:
biophysical considerations. The Philippine Agricultural Scientist 89, 34–47.
43. Primavera, J.H. 1998. Tropical shrimp farming and its sustainability. In: Tropical
Mariculture. De Silva, S.S. (ed). Academic Press, London, pp. 257–289.
44. Alin
˜o, P.M., McManus, L.T., Fortes, M.D., Trono, G.C., Jacinto, G.S. and Yap, H.T.
1994. Calauag Bay Resource and Ecological Assessment. Final Technical Report,
Environmental Primemovers of Asia, Inc., Philippines, 305 pp.
45. Stevenson, N.J., Lewis, R.R. and Burbridge, P.R. 1999. Disused shrimp ponds and
mangrove rehabilitation. In: An International Perspective on Wetland Rehabilitation.
Streever, W. (ed). Kluwer Academic Publishers, Netherlands, pp. 277–297.
46. The authors are grateful to several funding agencies (11, 12, 19–21) making possible all
these surveys covering a wide geographic area across the country. We are also indebted
to a long list of local people assisting us in the task of cutting across these mangrove
forests and for always making such experiences full of fun despite the extreme logistical
difficulties. We thank the two anonymous reviewers for their valuable suggestions.
47. First submitted 11 May 2007. Accepted for publication 16 September 2007.
Maricar S. Samson works on various aspects of mangrove
restoration leading toward her PhD degree in environmental
science and management. She has also worked in several
projects dealing with the management of coastal zones
including policy reviews. Her address: The Marine Science
Institute, College of Science, University of the Philippines,
Diliman, Quezon City 1001 Philippines.
E-mail: msamson@upmsi.ph
Rene N. Rollon is an associate professor at the Institute of
Environmental Science and Meteorology, University of the
Philippines, Diliman, where he studies various aspects of the
biology and ecology of seagrasses and mangroves. His
address: Institute of Environmental Science and Meteorology,
College of Science, University of the Philippines, Diliman,
Quezon City 1101 Philippines.
E-mail: rnrollon@up.edu.ph
240 Ambio Vol. 37, No. 4, June 2008ÓRoyal Swedish Academy of Sciences 2008
http://www.ambio.kva.se