Mangroves And Climate Change Observations Of Two Mangrove

GTZ KIEN GIANG BIOSPHERE RESERVE PROJECT
MANGROVES AND CLIMATE CHANGE
Observations of two mangrove areas of Kien Giang Province,
including the districts of Hon Dat and An Minh
TECHNICAL REPORT 08E1108NORM
2008
Mangrove and Climate Change -Observations of two mangrove area of Kien
Giang Province, including the districts of Hon Dat and An Minh
A report by Dr. Norm Duke
Published by:
Deutsche Gesellschaft fuer
Technische Zusammenarbeit (GTZ) GmbH
- German Technical Cooperation -
Conservation and Development of the Biosphere Reserve
of Kien Giang Province Project,
Department of Science and Technology,
320 Ngo Quyen Street, Rach Gia City,
Kien Giang Province, Vietnam.
T
+84 77 3942 937
F
+84 77 3942 938
E
[email protected]
I
www.gtz.de/vietnam
Responsible:
Dr. Sharon Brown, Project "Conservation and Development of the
Biosphere Reserve of Kien Giang Province
Author:
Norm Duke – Section leader – University of Queensland
© gtz, 2009
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Aims and objectives
As stated, the overall objective of the assignment was to support the Department of
Agriculture and Rural Development (DARD) to design a land use model that
maintains the integrity of mangrove forests in four coastal districts of Kien Giang
Province.
Specifically, this was to include:
1. Visits to three coastal districts and describe the importance of mangroves for
livelihood, biodiversity and health of the mangrove forests.
2. Visit Binh Son Commune, Hon Dat District and contribute to the design of a
Land use model by providing advice on the best strategy for planting
mangroves in areas of strong sea current where the sea dyke is being
eroded.
Disappearing dyke endangers coastal communities in Hon Dat District.
Can mangroves help?
3
Stated Background in ToR
Kien Giang is a coastal province, so mangrove forest plays a very important role in
the mitigation of the effects of climate change, such as increased typhoons and sea
level rise, and also supports the economic development of tourism, coastal protection
and aquaculture. The local farmers living in the mangrove belt seem to have limited
knowledge for and techniques on appropriate forest management and aquaculture.
The mangrove belt is in parts very narrow and therefore has poor capacity for
resilience and a limited capacity to mitigate the effects of climate change. The
biodiversity of the mangrove belt has not been described. Specific negative impacts
from the people on the coastal protection forest need to be identified. In Hon Dat
District strong sea currents are eroding a dyke that is meant to protect the local
people and their agricultural land from inundation during storms. The Province and
District authorities have tried to grow mangroves in these areas but have failed. New
technical approaches need to be tested in this area.
Approach followed in this study
The initial visit was essentially to make introductions with project goals and site
locations, to meet with key project staff, along with the staff of DARD and DoST, and
community leaders. Whilst developing this network, two key sites visits were made to
gain a personal and practical understanding of the stated project goals in the field.
This was achieved with site visits to Hon Dat and An Minh Districts. The outcomes of
these meetings and site visits are presented in this report.
Fig. 1. Two sites visited in Kien Giang Province – districts of Hon Dat and An Minh.
4
Key outcomes
The key findings presented are grouped under three sections:
1. Biodiversity surveys.
2. Hon Dat model assessment.
3. Forest utilization and benefits.
With each of these key findings, the chief points include: initial observations; along
with deductions and suggestions for pragmatic, achievable outcomes.
Definition of mangroves
Mangroves are special group of plants, able to tolerate and thrive in saltwater and
saturated soils. The word ‘mangrove’ refers to the habitat in the same way as we
think of ‘rainforest’ with its mixture of plant types. Sometimes the habitat is called a
‘tidal forest’ or a ‘mangrove forest’ to distinguish it from the trees that are also called
mangroves.
A mangrove is a tree, shrub, palm or ground fern, generally exceeding one half metre
in height, that normally grows above mean sea level in the intertidal zone of marine
coastal environments and estuarine margins. A mangrove is also the tidal habitat
comprising such trees and shrubs.
1. Biodiversity surveys – first observations
Mangroves of Kien Giang Province
Mangroves often makeup fragmented fringe vegetation along canal margins where
they cross Mekong delta lands, increasing in density towards the sea. Along the sea
edge, mangroves form occasionally significant barriers to storm waves, but all too
often this barrier is now breached. The effects are readily seen with varying patches
of eroded and uprooted trees along the sea edge, eroded dyke walls, and saltwater
intrusion into delta farmlands. The traditional response has been both to rebuild and
strengthen damaged dyke, and to plant mangroves in front. Where this failed, the
only option was to retreat, forcing people to relocate. In recent years, unfortunately,
this outcome has become more common. This has prompted calls to rethink past
rehabilitation techniques, and to gain a greater understanding of the biology and role
of shoreline vegetation, like mangroves. More than ever, it is time to develop more
effective ways of managing threatened coastal margins better by learning how to use
mangroves more effectively. This report briefly addresses these questions, and
describes the mangroves in Kien Giang, as is known.
In the first instance, it seems there are few reports describing the mangrove species
of Kien Giang Province, or those of neighbouring provinces in the Mekong delta. A
brief literature search and communication with a Vietnamese botanical mangrove
specialist was undertaken prior to this survey to gain some background information.
A short meeting was organised in Ho Chi Min City with Dr. Vien Ngoc Nam from the
5
HCM City University of Agriculture and Forestry. Dr Nam is a recognised specialist in
mangrove studies in Vietnam. With this meeting, the current list of mangrove species
for Vietnam (Table 1) was compiled for this report. As a result of these enquiries,
there appear to be at least 39 species, and some additional ones are likely. One
species, Sonneratia apetala, appears to have been introduced to some areas in the
north. The additional ‘expected’ species are recognised hybrid species - observed in
other countries where both parental species co-occur. Several such parental couplets
exist in Vietnam, hence the opportunities for similar hybridization here. So, some
hybrid individuals are expected to be found.
The current list shown in Table 1 extends previous lists for Vietnam (based on
recognised mangrove species elsewhere), including: the World Mangrove Atlas lists
29 species (Spalding et al. 1997); Prof. Phan Nguyên Hồng (2004) listed up to 34
species; and Dr. Vien Ngoc Nam lists 36 species (personal discussions, 2008). No
additional species have been added with the current survey, so the 39 recorded here
were derived from the combination of previous lists. Dr Nam is responsible for two
recent additions, including Pemphis acidula and Bruguiera hainesii (see, Nam 2008).
In general, the long and featured tropical coastline of Vietnam, mostly facing the
South China Sea, is ideal for mangrove biodiversity, growth and development.
Mangroves are accordingly found from the furthest northern parts of the country to
the southern-most parts. However, mangrove areas have significantly declined in
recent years, from possibly around 4,000 km2 to today’s estimate of around 2,700
km2 (Spalding et al. 1997). Much of this loss reportedly occurred during the Vietnam
War (1962-1972) when about 1,050 km2 (36%) of mangrove forests were destroyed
by the widespread use of herbicides and napalm to defoliate extensive once forested
areas in the south. The legacy of this use of harsh and arguably long-lasting
chemicals is reflected in today’s recovering second growth stands of shrubby growth
and reduced biodiversity. The largest areas of mangroves today are found in the
south, notably in the Mekong delta and particularly in the province of Ca Mau.
In general, maximal biodiversity of mangrove species occurs in the south. The
number of species is reportedly less in the north since seasonally cooler
temperatures limit growth and reproduction.
Notes on the mangrove and associated species observed in Kien Giang
Surveys were conducted during two days, 16 and 18 October 2008, by N.C. Duke, S.
Brown and P. Nguyen. Two localities in Kien Giang Province were visited, including
the Districts of Hon Dat and An Minh – north and south of Rach Giá, respectively.
Notes are given on the flowering and fruiting condition, plus other brief observations,
including distinguishing characters.
Ô rô trắng - Acanthus ebracteatus
Observed only in Hon Dat District on this occasion.
Mostly without flowers or fruits. A rare flower allowed accurate description and
identification. Generally, spiny leaves and stems. Stems notably purplish in colour.
Mostly observed as straggly patches under the canopy of Sonneratia lanceolata and
Nypa fruticans.
6
Ô rô tím - Acanthus ilicifolius
Observed only in An Minh District on this occasion.
Mostly without flowers or fruits. Some uncommon flowers and fruits allowed accurate
description and identification. Notable spiny leaves and stems. Stems green in
colour. Mostly observed as dense thickets between and amongst Avicennia alba
stands.
Ráng - Acrostichum aureum
Dark brown spores on upper leaf undersurfaces.
Stream edge in canals. Not present along the coastal foreshore.
Ráng - Acrostichum speciosum
New golden brown spores on upper leaf undersurfaces.
Undercanopy plus stream edge clumps.
Mắm trắng - Avicennia alba
Immature and mature fruits common – no flowers observed.
Dominant and common spreading trees along foreshore and lower canal edges.
Mắm biển - Avicennia marina
Mostly without flowers or fruit. However, a few flowers and mature fruit were collected
allowing identification.
Occasional shrubby trees along coastal foreshore, amongst Avicennia alba.
Mắm lưỡi đòng - Avicennia officinalis
Observed only in An Minh District on this occasion.
One individual observed. No flowers or fruits present. Distinguished by its glossy
ovate leaves with rounded apices.
Vẹt trụ - Bruguiera cylindrica
Mature flower buds, flowers and hypocotyls.
Occasional columnar, erect small trees to 5-6 metres. Exposed and threatened by
erosion.
Vẹt dù - Bruguiera gymnorhiza (see Fig.2)
Observed only in Hon Dat District on this occasion.
Mature hypocotyls, occasional immature fruit.
Occasional, erect small trees to 5-6 metres. Exposed and threatened by erosion.
Vẹt khang - Bruguiera sexangula
Mature flower buds, with occasional mature hypocotyls.
Occasional columnar, erect small trees, often emergent. Many stands eroded and
threatened by erosion where they appear to have been more dominant previously.
Dà quánh - Ceriops decandra
Observed only in An Minh District on this occasion.
Observed with immature fruits.
Occasional small bushy trees under canopy of other species, like Rhizophora
apiculata and Bruguiera cylindrica.
Quao nước - Dolichandrone spathacea
Observed only in An Minh District on this occasion.
7
Commonly with dry, dangling mature seed pods. Flowers rarely observed.
Observed as occasional spreading small trees along upper estuarine sections of
canal margins.
Giá - Excoecaria agallocha
Mostly sterile, a few bud primordia and rare flowers observed suggesting the
imminent onset of flowering.
Occasional trees amongst other species, namely Sonneratia lanceolata and
Rhizophora apiculata.
Cóc đỏ - Lumnitzera littorea
Observed only in Hon Dat District on this occasion. A single small tree observed on
the foreshore of the eroding shoreline fronting the model area. Threatened by
erosion.
Immature flower buds only – but enough to identify the species. Red petal shown,
combined with terminal position of inflorescence.
Cóc vàng - Lumnitzera racemosa
Mostly without flowers, some rare mature fruit collected.
Single small tree and shrubby bushes observed on foreshore of eroding shoreline.
Threatened with erosion.
Dừa nước - Nypa fruticans
Mostly without flowers or fruit. However, rare immature fruit observed.
Occasional clumps along canal margins, and amongst other species along the
coastal foreshore.
Đước đôi - Rhizophora apiculata
Mature flower buds and open flowers mostly. A small number of mature hypocotyls
observed.
The only species of this genus observed. Mostly occurs along the seaward fringes
along the coast and the mouths of canals.
Bần trắng - Sonneratia alba
Mostly without flowers or fruits, but rare mature buds and immature fruit collected.
Absent in most areas. Occasional trees around the canal mouth feeding into the
depositional bank area. Coexists occasionally alongside Sonneratia lanceolata in
these areas. Also notable in mixed stands with Avicennia alba.
Bần chua - Sonneratia lanceolata (=S. caseolaris)
Mature flower buds, flowers and occasional mature fruits.
Common and dominant mangrove in the region. Notable in canal stands as well as
along the coastal foreshore fringe where it is associated with canal mouths.
Bần ổi - Sonneratia ovata
Mature flower buds, flowers and occasional immature fruits.
Notable for its conspicuous appearance with dark green spreading canopies of large
rounded leaves. The occurrence of such trees was easily observed from afar. In Hon
Dat District, four trees were identified along the coastal foreshore between the two
canal mouths surveyed.
Xu ổi - Xylocarpus granatum
8
Observed only in An Minh District on this occasion.
No flowers or fruits observed. Identification based on foliage characters, mostly its
compound leaves. One mature tree observed in a farmed area.
Associate mangrove species
Tra (Tra làm chiếu) - Hibiscus tiliaceus
Occasional shrubby bushes on canal edges.
Tra biển (Tra làm vồ) - Thespesia populnea
No flowers or fruits observed.
Occasional shrubby bushes on canal edges.
Ngọc nữ biển (Vạng hôi) Chùm gọng - Clerodendron inerme
Flowers observed.
Occasional small thickets along canal margins.
Sedges
Few sedges and salt marsh species observed.
Introduced species
Na biển (Mãng cầu) - Annona glabra (Pond Apple)
Mature fruits on many plants.
Shrubby bushes to 1.5 m tall.
Notable presence along canal margins and amongst gardens. Not established
whether it is being cultivated and used – or, tolerated, ignored.
Trâm ổi – Eugenia spp., Eucalyptus spp.
Cultivated and spreading in many areas – growing commonly along roadways and
bund walls
Tràm - Melaleuca spp., M. cajuputi
Cultivated but no obviously spreading.
Nuciflora sp. (Coconut)
Not common. Occasional tree. Said to be affected badly by leaf curl – with grubs
eating the leaves and using them for young developmental stages.
9
Table 1. Mangrove plant species in Hon Dat and An Minh districts compared with all
Vietnam (Hong 2004; Nam 2008; Duke deductions). *Introduced. (?) not reported,
possible.
Latin Name
Ô rô trắng
Ô rô tím
Ráng
Ráng
Sú
Sú đỏ
Mắm trắng
Mắm biển
Mắm lưỡi đòng (Mắm đen)
Mắm quăn
Tim lang
Vẹt trụ
Vẹt dù
Acanthus ebracteatus
Acanthus ilicifolius
Acrostichum aureum
Acrostichum speciosum
Aegiceras corniculatum
Aegiceras floridum
Avicennia alba
Avicennia marina
Avicennia officinalis
Avicennia rumphiana
Barringtonia racemosa
Bruguiera cylindrica
Bruguiera gymnorhiza
Bruguiera hainesii
Bruguiera parviflora
Bruguiera sexangula
Bruguiera X rhynchopetala
Ceriops decandra
Ceriops tagal
Cynometra ramiflora (not)
Dolichandrone spathacea
Excoecaria agallocha
Heritiera littoralis
Kandelia candel
Kandelia obovata
Lumnitzera littorea
Lumnitzera racemosa
Lumnitzera X rosea
Nypa fruticans
Pemphis acidula
Rhizophora X annamalayana
Rhizophora apiculata
Rhizophora X lamarckii
Rhizophora mucronata
Rhizophora stylosa
Scyphiphora hydrophylacea
Sonneratia alba
Sonneratia apetala
Sonneratia X hainanensis
Sonneratia lanceolata (=S.
caseolaris)
Sonneratia ovata
Sonneratia X urama (=S. X gulngai)
Xylocarpus granatum
Xylocarpus moluccensis (ex X.
mekongensis)
Xylocarpus rumphii (ex X.
moluccensis) (not)
TOTAL SPECIES
Vẹt tách
Vẹt khang (Vẹt đen)
Dà quánh
Dà vôi
Quao nước
Giá
Cui biển
Trang
Trang
Cóc đỏ
Cóc vàng
Cóc hồng (cây lai)
Dừa nước
Đước (Đước đôi)
Đưng (Đước bộp)
Đâng (Đước vòi)
Côi
Bần trắng
Bần chua
Bần ổi
Xu ổi
Xu mekong
Xu sung
An
Minh
Kien
Giang
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
Hon
Dat
Local Name
10
1
1
1
Vietnam
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
(?)
1
1
1
1
1
1
1
1
1
1
1
1
(?)
1
1
1
1
1
1
1*
(?)
1
1
(?)
1
1
16
18
21
39 (+4?)
Current Issues concerning biodiversity
1) There is an urgent need to fully quantify species presence, to train local
technical officers and academics in species identification, and to maintain a
reference collection.
2) Each local species needs to assessed for its growth conditions, its ecological
preferences, its relationships with a range of chemico-physical factors, and its
potential benefits.
3) Since there has been considerable land disturbance over many centuries,
mangrove species are expected to have fragmentary and discontinuous
distributions. This means that some species will be uncommon and rare
making them vulnerable to further disturbance.
4) Potential for mutations and strange morphological characteristics is high given
the high levels of herbicides deployed in this region during the war of the
1970’s. This may also have caused the loss of some species in some localities
so there may be a need for their re-introduction and replenishment from
neighbouring occurrences.
Suggested Responses and Proposed Projects
1) Develop and maintain a Reference Collection of mangrove plant species and
their associates. Specimens can mostly be kept dry, with some bulky parts
preserved in alcohol.
2) Conduct training workshops coupled with field visits to develop plant
identification techniques. This will encourage self reliance and accurate
reporting by Vietnamese project technical officers.
3) Couple field based biodiversity studies with remote sensing using aerial
photographs, satellite imagery and small aircraft, if possible. Develop resource
maps showing mangrove stands, and dominant mangrove community types,
where possible.
4) Extend biodiversity surveys to other promising areas, like Phu Q’uoc.
5) Produce informative brochures for both training and general awareness
raising.
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Fig. 2. Training and reporting are bolstered by both physical and digital reference
collections.
2. Hon Dat Model Site: a preliminary assessment of the role of
mangroves
Mangrove condition in the Model Site area
As stated, the proposal identified the need for a pilot land use model in Hon Dat
District. Benefits of this approach are considerable, including: localised quantification
of coastal processes, along with the testing and evaluation of practical rehabilitation
strategies to identify the most effective means to successfully stabilize the eroding
coastal margin. Up to this time, several strategies have been implemented;
unfortunately, few if any have been successful in the Hon Dat site. It is the purpose of
this brief investigation to review the current situation, and the role of mangrove
plants. In such circumstances, it is critical to determine whether mangrove vegetation
is able to have a positive influence on future rehabilitation – with assertive
intervention strategies, like planting and the installation of wave barriers.
12
Fig. 3. Close view of the Hon DAT Model Site, showing key erosion areas and
existing strategies.
The chosen site was inspected on 16th October 2008. Access to the site was made
by boat launched from a large canal to the north. With the calm seas of the day, it
was possible to approach the site and land the vessel to make efficient assessments
of both frontal stands, and rear upland edge conditions of the current mangrove
fringe. Our field observations were enhanced further by the use of previously
obtained Google Earth images of the site and surrounding areas (Fig. 3).
The overall condition of the site and processes are illustrated in a conceptual
diagram (Fig. 4). In this diagram are listed the dominant processes and pressures
influencing the coastal fringe of the Model Site in Hon Dat District. These are
summarised in seven dot points:
1. Coastal retreat is readily shown by sections of eroding foreshore, breached
dyke, undermined edge trees, no depositional bank, and fruit trees killed by
saltwater intrusion.
2. Strong flows into sea across mud banks and delta - derived from rain and
Mekong River.
3. Use of canal tidal gates to control intrusion of sea water into canals.
4. Fish traps associated with depositional banks – but abandoned in areas
fronting the eroding seaward edge.
5. Fresh water obtained from bores to 30m depth, situated within 10s of metres
inside the dyke.
6. Surface sediments mostly marine muds & deeper sediments possibly sandy
acts as an aquifer.
7. Significant areas of flooded farm pond enclosures – growing a variety of crops
from fish to rice, to trees. The latter include fruit and timber trees. There is little
or no use of mangroves other than for sanitary purposes, casual collecting
sites, vessel mooring, and primary seashore buffer vegetation. Elsewhere
nearby mangroves are used far more extensively.
13
Fig. 4. Conceptual model showing heavily utilized coastal environment and the chief
processes associated with the eroding shoreline of the Model Site at Hon Dat District.
Current Issues at the Hon Dat Model Site
1)
2)
3)
4)
5)
Erosion despite barrier protection
History of dyke retreat despite best efforts
Predicted sea level rise (like >17 cm/100 y)
Fishing areas abandoned in front of eroding dyke
Dismal seedling planting success despite best efforts. It is essential at this
time to review all aspects of past efforts. To identify any successful plantings
and to learn by more considered re-evaluation of international best practice.
Initial site observations suggest planting depth below mean sea level might
have contributed to poor planting success (see Fig. 5).
6) The poor success of planting in Hon Dat is not unique to this location. There
are currently no published or otherwise recognised best practice techniques
for this kind of restoration. It is possible that, in the face of anticipated sea
level rise, there may be no relatively simple solutions. This possibility must be
considered in future assessments to minimise further project outcomes that
have few expectations of success.
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Fig. 5. Diagram showing the preferred
planting zone – the ‘mangrove sweet
spot’ between mean sea level (MSL) and
the Highest Astronomical Tide (HAT).
Suggested Responses and Proposed Projects
1) The Hon Dat Model Site project should ideally be part of a National strategy to
develop effective ways to deal with sea level rise and climate change – a
National Sea Level Rise Action Plan.
2) Based the Hon Dat Model Site, and others, there needs to be a cost-benefit
assessment of alternate longer term, ‘big picture’ options, like:
(A) Adaptation – retreat and relocate infrastructure and people;
(B) Defence – construction of elevated dykes and locks will be costly, and
they will increase threats from tsunamis, and severe storms; and
(C) Adaptation and Defence – an option so far receiving very little attention,
being to progressively raise delta land levels by ‘top dressing’ farmed areas at
the same rate as sea level rise.
3) Survey and Baseline Monitoring of the Hon Dat Model Site needs to
commence immediately. This survey part would include three components: (A)
physical environment - spatial mapping of site, mapping of bathymetry fronting
the site with elevation profiles for foreshore margins, coupled with an elevation
model of surrounding lands; (B) water condition – current movements along
shore, wave energy and direction with various weather conditions; and (C)
biotic habitat condition – assessment of existing forest structure and species
present (including fauna), a survey of seedlings present, their physical
location, and their growth history. Accurate contour mapping is needed across
all proposed planting areas to ensure seedlings are planted in areas most
suitable to their survival and establishment.
4) Historical mapping is needed to develop a timeline of past change. For
example, it is important to quantify rates of earlier change, and to identify prior
features like the earlier (now eroded) dyke some 100 m further seaward.
5) Site Monitoring would best commence at six-monthly intervals and continue for
at least 3 years. After this, it would be beneficial to continue monitoring at
annual or bi-annual intervals depending on the rates of change observed.
6) Regular monitoring requires well-trained local staff. Scientifically sound
practices are essential if the stated longer term objectives are to be achieved.
Specialist trainers and staff need on-going support.
7) Produce informative brochures for both training and general awareness
raising.
15
3. Forest utilization, products and benefits
Benefits of Mangroves
The benefits of mangroves are summarised and listed in many international
publications (Tomlinson 1986; FAO 1994; Hogarth 1999; Saenger 2002). Rural
communities in mangrove areas of Vietnam also have a good working knowledge of
the range of products mangroves have on offer. These briefly include:
1) Coastal buffering, protection for stability.
2) A good place to catch fish, shellfish and crabs.
3) Habitat for marine life to live and grow (breeding ground).
4) Shelter for small marine life to hide and avoid prey species.
5) Carbon sequestration both in timber biomass, as well as in organic rich soils of
often deep mangrove peat.
6) A source of foliage for attracting fish to nearshore fish traps.
7) Timber for house construction, boats, cooking, fishing poles, furniture.
The Mangrove House
Perhaps one of the most remarkable examples of mangrove utilisation was observed
in a small farmers cottage in An Minh District. The owner, Nguyen Van Thong, has
made extensive use of mangrove timber products in its construction and fittings. The
timber frame was made from poles of Rhizophora apiculata (Đước), the walls were
made from wide planks of Avicennia alba (Mắm), the thatched skillion was made from
fronds of Nypa fruticans (Dừa nước), the house steps were made from wood blocks
of Avicennia alba (Mắm), the furniture inside was made from timber of Xylocarpus
granatum (Xu ổi) and Rhizophora apiculata (Đước) (all varnished to show off the
beautiful timber grain), the cooking fuel (charcoal) was made from Avicennia alba
(Mắm), and food in preparation was mangrove crabs (Sesarmids). All these
mangrove products were harvested from the mangrove forest gardens surrounding
the house.
The Mangrove Garden
Another house unusually featured a mangrove garden bordering the canal edge
waterfront. The mangroves used in the garden included a short hedge of Bruguiera
sexangula (Vẹt khang) seedlings, and Dolichandrone spathacea (Quao nước)
bushes at intervals. The effect was quite effective and attractive. The added
functional bonus is that this vegetation will help stabilise the canal property boundary
which is clearly eroding in other places with the regular and frequent passage of
powered vessels along the canals.
16
Current Issues – encouraging greater appreciation and utilization of
mangroves
These activities appear limited to only a few individuals in the community at present.
However, this small scale utilization of mangrove products could easily be expanded
with an awareness raising campaign, coupled with the development of a supply
source for such products.
The mangrove house and garden clearly demonstrate that there are readymade local
champions in the community of people who know some useful benefits of
mangroves. The expectation is that they would need little encouragement to expand
this interest, to advise others, and to amplify the underlying message that mangroves
have useful benefits.
Each of these examples, in this way, might be scaled up to provide income support
for a number of people within the community. The most promising project would be
the supply of quality mangrove timber products, using the Cannonball Mangrove,
Xylocarpus granatum (Xu ổi), in the first instance.
Suggested Responses and Proposed Projects
1) Mangrove quality timber plantation model. There needs to be an assessment
of a livelihood project based on the mangrove Xylocarpus granatum for its
quality timber. The assessment needs to investigate the market and potential
demand for this timber, as well as the ability to both grow the trees and
harvest them.
2) Mangrove carbon neutral energy production. As shown with the Matang
mangrove forests of Malaysia, Rhizophora apiculata can be grown in a 30
year crop rotation for the production of charcoal for cooking and heating. This
mangrove species is easy to plant and grow. Covering an area of more than
40,000 ha, the Matang industry shows that the production is sustainable,
having been managed for over 100 years. This forest industry would provide
local jobs, ready fuel, and significant Green advantages – not the least of
which being a renewable carbon energy source. Extensive areas of the region
could easily be converted to mangrove timber production. And, in the face of
rising sea levels, the crop would be less troubled by saline encroachment and
inundation.
3) Produce informative brochures for both training and general awareness
raising.
© gtz, 2009
Deutsche Gesellschaft für
Technische Zusammenarbeit (GTZ) GmbH
- German Technical Cooperation Conservation and Development of the Biosphere Reserve
of Kien Giang Province Project,
Department of Science and Technology,
320 Ngo Quyen Street, Rach Gia City,
Kien Giang Province, Vietnam.
T
+84 77 3942 937
F
+84 77 3942 938
E
[email protected]
I
www.gtz.de/vietnam
17
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