CanGio Mangrove
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DON Vietnam
Impact of MAngrove exploitation of the Benthic ecosystem and assessment of Ecological quality objectives -Vietnam and Belgium cooperation

  Cangio Mangrove


Mangrove forests have made considerable contributions to the socio-economic development of Vietnam, particularly of the coastal communities. Such contributions include the supply of fuel wood, charcoal, poles, construction materials, pulp, etc. Besides the direct economic value of wood and fuel, mangroves also play an important role in the sustained production of fish, prawns, cockles, crabs, etc. and are vital to the long-term stability of coastal fisheries.

However, in recent years, there has been a growing conflict in the use of mangrove lands with the conversion of mangrove forest land to aquaculture involving embanking and barricading of waterways within the forest to raise shrimp. Such activities increasingly threaten not only the stability of the mangrove ecosystem, but also the livelihood of the coastal communities who traditionally have been dependent on the mangrove resources for their income and subsistence.

Mangrove forests in South Vietnam up to 40 decade of the 20 century were consisted of about 250,000 ha. This is one of the most important ecosystems in Vietnam in terms of socio-economy and environment. Prior to 1975, Can Gio mangrove forest covered an area of 40,000 ha; the canopy was dense, with trees over 25 m tall and 25-40 cm in diameter. During period of Vietnamese war (1961-1971), about 104,939 ha mangrove forest in South Vietnam was destroyed by different herbicides. After many years of herbicide spraying here still remains shattered bushy or bare land.A great effort of local people after wars is the rehabilitation of 22,000 ha of mangroves. To day, Can Gio has became one of the most beautiful and extensive sites of rehabilitated mangroves in the world. For its high significance the Can Gio mangrove forest has been officially recognized in 2000 as one of the world's Biosphere area by UNESCO/MAB. And now Can Gio mangrove forest is a priority region for promoting interdisciplinary research, training and communication in the field of ecosystem conservation and the rational use of natural resources.

The rapid population growth and industrial activities, in tandem with the environmental movement, have brought to focus the problem of environmental degradation which threatens the well-being or even survival of population communities. Hence, it is necessary to adopt or develop technologies, which shall give us better understanding of the factors and processes responsible for the deterioration of the physical environment, as well as people who can apply and develop such knowledge. It is likewise necessary to have reliable benchmark information on the condition of the physical environment to prevent depletion, destruction or degradation, or at least permit man to determine the rate of depletion that may be consistent with sustainable growth or steady state development. It is in this context in which the value of an Environmental Assessment Project must be viewed.

Environmental problems, therefore, are the inherent consequences of nation building as the extraction and processing of natural resources such as oil, water and precious metals, and the use of soil and water systems constitute the basic activities for economic growth. As economic development progresses from agriculture to industrialization, more and more resources have to be extracted from the environment. Coupled with exponential growth of human population, environmental problems increasingly demand major concern and concerted effort on the local or regional level.

Specifically, industrial activities, economic development and rapid population growth are among the major sources of stress on the water pollution environment, factors that are indispensable or inevitable within the local context. In Vietnam, industrialization and modernization is in progress. The socio-economic development planning requires an environmental protection plan since-as lessons learned from other developing countries in Southeast Asia-the indiscriminate use and mismanagement of natural resources brought about by poorly planned and inadequately studied urban and agricultural expansions, human settlements, estate development, fishery activities and tourism may cause severe problems such as: destruction of mangrove forests and watersheds; degradation of agricultural land; air and water pollution; destruction of coastal ecosystems; and solid and liquid wastes disposal. Therefore this Project "Impact of mangrove exploitation on the benthic ecosystem and the assessment of ecological quality objectives (IMABE)" would be taken an important role in the education and research on biodiversity, biomonitoring and environmental awareness in Vietnam and should help to prevent the loss of many endemic species and diverse of benthic ecosystems and contribute to the sustainable exploitation of mangrove ecosystem


Ho Chi Minh City (formerly Saigon) is located about 1,300 km south of Hanoi and includes a mangrove area in Can Gio District. Originally the name was Can Gio, then, from 1975-1991 it was named Duyen Hai District but on December 18, 1991 it was given back its original name, Can Gio, by the Council of Ministers. Can Gio District (located at latitude 22' 14" - 40' 00" N, longitude 106o ­107o 00' 50" E) is about 65 km south of Ho Chi Minh City. It is one of 18 districts of Ho Chi Minh City and covers an area of 73,361 hectares. From the north to the south it covers a distance of 35 km and at the middle portion, is about 30 km wide. A network of rivers and channels traverses the delta and the main waterways leading to the port of HCMC.

From 1964-1970, Can Gio District, like many other mangrove areas, was sprayed heavily with herbicides: 665,666 gallons of Agent Orange, 343,385 gallons of Agent White and 49,200 gallons of Agent Blue. As a result, 57% of the mangrove forest in this district was destroyed (Ross, 1975). In some areas large trees of Rhizophora, Sonneratia, and Bruguiera were killed by the herbicide spraying and in many areas the vegetation was completely destroyed. Only Avicennia and nipa palm were able to survive and regenerate after the application of herbicide. And new species such as Phoenix paludosa and Acrostichum aureum, a fern which presently dominates elevated land, have expanded. Some individual trees of Avicennia officinalis and Excoecaria agallocha are now found only as shrubs. After many years of chemical spraying, the degraded land still has only scattered small trees of Avicennia, Ceriops, Lumnitzera, Thesphesia, Pluchea, or Sesuvium portulacastrum and Paspalum vaginatum. Since 1978, a vast programme of reforestation has been undertaken by Ho Chi Minh City Forestry Department with the main species being Rhizophora apiculata. Up to now, the reforestation effort has brought vast ecological improvements to the environment. Wild animals such as monkeys, otters, pythons, wild boars, crocodiles and various kinds of birds have returned to the artificially regenerated mangrove forests. Since 1991, the Can Gio mangrove forest has been declared an "Environmental Protection Forest" by the Council of Ministers (Decree No. 173 CT/H date May 29, 1991).


The climate is typically monsoonal with a pronounced dry season from November to April and a wet season starting from mid-April and lasting until late October. The average annual rainfall is about 1,336 mm with most of the rain concentrated in June and August, during the wet season. The total number of rainy days per year is about 160. The mean monthly rainfall amounts to 110 mm. Insolation is 5-9 hours per day of sunshine. Solar radiation is 300 cal/cm3 Potential evapotranspiration in the area amounts to 4 mm/day, 120.4 mm/month and the highest in June (173.2 mm). The mean annual relative humidity is 80%. The winds are into the west, generally with wind speeds at about 2m/sec and typhoons are rare. The tidal regime is semi-diurnal, ranging from 2 m at mean tides to 4 m at spring tides. Alluviated soils are the principal soil type. These soils are generally slightly acidic (pH values of 4.5-6.5). Soils are predominantly saline sulphatic clay or mud with large quantities of sulfites which become oxidized to sulfates and hence acid when exposed to air.

Flora and Fauna of Can Gio Mangrove Area

About 105 plant species, belonging to 48 genera (Nam et.al. 1990) are found in Can Gio mangrove forest, including Rhizophora apiculata, Bruguiera gymnorrhiza, Bruguiera parviflora, Ceriops sp, Kandelia candel, Rhizophora mucronata, Sonneratia alba, Sonneratia ovata, Sonneratia casedar, Avicennia alba, A. officinalis, A. lanata (stunted trees in abandoned salt fields), Aegiceras majus, Thespesia populnea, Hibiscus tiliaceus, Lumnitzera racemose, Xylocarpus granatum, and Excoecaria agallocha.

There are about 440 known species of aquatic fauna. The fish fauna is very abundant since mangrove forests serve as nurseries as well as sources of foods for many species of fish like Lates calcarifer and Mugil affinis, prawns such as Pangasius spp, Penaeus spp., Metapenaeus spp., and mudcrabs: Scylla serrata.

Within the area, there is a variety of wildlife such as wild pig (Sus scrofa), monkey (Macaca fascicularis), otter (Lutra lutra), saltwater crocodile (Crocodylus porosus), many species of snakes etc., which are now endangered or have dissapeared due to human interference. There are also many birds, including migratory species, some of which are very rare and should be protected.

Social Information

Census Abstract of Can Gio District, HCMC (2004)


 Commune  Total
 Binh Khanh  16.165
 An Thoi Dong  11.231
 Tam Thon Hiep  4.865
Ly Nhon  4.569
 Thanh An  4.241
 Long Hoa  9.527
 Can Thanh  9.706

Land Use

Three major types of monoculture plantations are found in Can Gio: Rhizophora, Eucalyptus and Nypa of which Rhizophora is the most important. The northern part of Can Gio District is a paddy producing region, but the rice yields are very low because of the acid sulphate soils or failure to prevent salty water intrusion. The southern part of the district is the most suitable area for Rhizophora species. The forest resource of the district covers an area of 26,225 ha or 36,7% of the total area. About 3,640 ha of shrimp ponds within the mangrove forest is operated by local people and state farms. With traditional harvest methods, 360 ha of semi-intensive shrimp ponds were established on abandoned salt pens, along the Nha-Be-Can Gio road, south of the district near the coast and on Phoenix paludosa land (grown on stiffer elevated sites). Now only 120 ha is in operation with an average yield of 350 kg/ha/year.

Land used in Can Gio


Area (ha)

Percent (%)

Forest plantation



Natural mangrove









Utilized land







Activities in Environmental Protection Forest

Following a study to determine the feasibility of converting a production forest into an environmental protection forest the Council of Ministers approved the conversion in Decree No. 173 CT/HDBT, dated May 29, 1991.

At the total cost of 500 million Dong (from the HCMC budget) 1,465 ha of Rhizophora apiculata, 101 ha of Nypa fruticans and 94 ha of Eucalyptus camaldulensis were planted and manpower and building support provided.

Laws and Regulations for Mangrove Forest Protection

Until recently there were few laws, guidelines or regulations for the preservation of the mangrove forests, but on 19 August 1991, the Council of State issued a Forest Protection and Development Law concerning the establishment, use and management of environmental protection forests.

Regulations for first and second thinning operations were also issued in 1984 and 1989 respectively, while the regulation for a third thinning is still being compiled.

The hunting of wild animals and birds in the mangrove area is now prohibited, according to official rules No. 1222/NN-LN dated 15 November 1991, issued by the HCMC Agriculture Service.

A temporary regulation (No. 178/LN-QD) dated 7 March 1992 of the HCMC Agriculture Service concerns contracts for hiring of households and management units for individual plots for forest protection. Based on these contracts, the money for paying forest guards and households will be made available from the HCMC budget every year.

In the future, many regulations and guidelines for the use of the environmental and protection forests for wood production, marine culture and wildlife conservation will be compiled to further contribute to the preservation and rehabilitation of the mangrove ecosystem in Can Gio District.


Now that the mangrove forests in Can Gio have been declared an environmental protection forest a particularly thorough management plan is necessary for the area encompassing the use of appropriate extraction techniques. Being located so close to a major and rapidly developing city like HCMC this should be considered urgent, since pressure on the mangroves is likely to increase in the near future. During the last few years, the Forest Department of HCMC has implemented various measures to tackle some of these issues. In order to further improve the interactions between all sectors and to enable the development of more successful strategies, the following policy and development issues should be addressed:

Promoting Public Awareness

The protection and use of the mangrove ecosystem requires an intimate understanding of the forest and environment that people live in. In the past, extension programmes, training activities, seminars, workshops and exhibitions on the mangrove ecosystem have received low priorities. The lack of awareness of the importance of the mangrove forests coupled with the poor state of the economy has led to damage of the forest. To win public acceptance and support on a national and local level for forestry programmes, social and community forestry projects should be carried out to promote awareness of conservation issues and mobilize the local people to participate in mangrove forest protection. Public campaigns and educational activities should be undertaken to make people more aware of the direct and indirect importance of mangrove forests, and of laws and regulations for the forest, and to provide guidance on forestry and fishery techniques, including aquaculture. This awareness campaign should also be directed towards decision makers outside the mangrove area.

Land Allocation

In the past, land and forest land was allocated only to state organizations, not to local people or individuals. Hence, conflicts of interest arose frequently between state organizations and authorities such as state farms or the Forest Enterprise and the local people. Mangrove forests were damaged, illegal cutting was common and the state farms were not able to protect the forest. The local people, who lived in or nearby the forests had no legal benefits from the forest, not even firewood for cooking. The HCMC Forest Department has initiated a change in policy by allocating land and forest land to local people for forest protection, maintenance and afforestation. For example in 1990, Can Gio' Forest Enterprise allocated forest and forest land in compartments 4 and 6 to 10 poor households in Tam Thon Hiep sub-district. Besides allocating land, other support is also provided such as financial support for house construction, to purchase boats and rice during the first 6 months as well as tree seeds and assistance and supervision of their forest-related activities. This has resulted in better protection of the forest. The forestry activities provide jobs for people through forest protection, thinning and afforestation. If they plant trees on the allocated land, they become the real owners of these trees and hence behave more responsibly. For various reasons, such as limited economic resources to support households in the initial period after the land has been allocated to them, land allocation is presently carried out slowly.

Based on these initial experiences from both the Duyen Hai Forest Enterprise and Can Gio People's Committee it is clear that forest land allocation to local residents has considerable benefits and efforts should be made to find the ways and means to continue with this programme. However, it is necessary to identify the overall benefits and ensure that both sides (receivers as well as the government) benefit equally. The effective duration of the land allocation contract should also be considered.

Land Use Planning

In order to ensure the overall sustainability of the mangrove area, including permanent and productive forest lands, agricultural land, shrimp ponds, fish farms, rivers etc. a land use plan specifying zones for each land use category should be drawn up. This will aid in creating harmony among economic interest groups within Can Gio District as well as ensure economic and environmental stability. This plan should form the basis of the land allocation programme. In order to ensure a sustainable system the government should naturally include privately owned lands as well.

Improving Standard of Living

Most people who live in the Can Gio mangrove area are poor and live under harsh conditions such as lack of fresh water, education and communication, with few job opportunities and the risk of malaria. As a means of raising the standard of living in the mangrove forest areas, the government should give a high priority to the provision of infrastructure like roads, hospitals, schools, electricity, and so on. In addition, the government should try to provide opportunities for job generating activities, for instance by offering low interest loans for investments in charcoal kilns, aquaculture, livestock breeding, agriculture and tree planting. In particular, there appears to be ample room for a sustainable expansion of the local charcoal industry. With its close proximity to HCMC, market opportunities should be favourable for a number of products. In the allocation of jobs or forest land, priority ought to be given to Can Gio mangrove population over outsiders.

Shrimp Breeding

A thorough evaluation should be made of all semi-intensive and intensive shrimp ponds already present in Can Gio. This is considered necessary in order to draw up policies and guidelines to support the spread of these models. Clear cutting of mangrove forests for conversion into shrimp ponds is now strictly forbidden and this rule may have to be amended. Although semi-intensive farming appears to be the best model, many improvements in management and techniques still have to be introduced to prevent further damage to the mangrove forest ecosystem. The Indonesian models which integrate trees in the shrimp ponds have now been introduced in Minh Hai province with promising results. These models should seriously be considered for introduction into Can Gio District. The "taungya" system would be especially suitable where new forest is to be established.

Energy Policies

Although they live in the mangrove area, people often lack firewood for domestic use. This is because most forests already have owners or because the area has been designated an environmental protection forest, hence with restricted access. People are only permitted to collect dry wood and, because this amount is limited, this often leads to illegal cutting. This calls for a solution to the energy problems facing the people. This can be done through the promotion of afforestation, by planting trees in homesteads, around schools, along roads and riverbanks. This may increase the local supply and, together with the promotion of fuelwood-saving cooking stoves, would reduce illegal cutting.

Besides providing support through the provision of tree seeds and/or saplings, rules and regulations may have to be amended to ensure that the benefits reach the people. Ways and means should be found so that wood from thinning operations can be supplied at a low price to villages and sub-districts by the sub-district People's Committee and forest rangers. In order to determine the present and future demand for firewood of Can Gio District, a more detailed survey of fuelwood demand and supply needs to be carried out.

Scientific Research

As an environmental protection forest, HCMC's mangroves have a number of problems which need to be solved to satisfy both the demands for protection and production. Unfortunately, research on mangrove forests has until now been given low priority by the authorities due to the small size of the areas involved. Even though some research has been carried out during the past 10 years, e.g. in the fields of species survey, thinning operations, charcoal processing and silvofishery, this has often been done in isolation and with little sharing of the results among all concerned. Furthermore, many issues remain, such as: species choice for replanting on elevated land and on abandoned salt fields; planting trials with measurement of erosion along riverbanks and the coastline; relations between mangrove forest and fishery; primary and secondary productivity; surveying wild fauna to set up a wildlife conservation scheme; possible environmental impacts of ecotourism; economic prospect of alternative mangrove products, etc. There is therefore a need for close and conscious collaboration between the concerned research agencies, to ensure that these activities will collectively produce the optimum benefits and avoid waste of scarce resources.

The establishment of a National Mangrove Committee should be considered in order to formulate policy guidelines on mangrove resource management at a national level. This committee should be multidiciplinary, representing forestry, fishery and wildlife expertise and should actively coordinate between the central, local and international mangrove research institutions.


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