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Ha Long Bay, Vietnam – a coastal ecosystem

A coastal ecosystem

This case study has been produced for the Access Asia program by secondary teachers travelling on a Teacher Education Visitation program to Vietnam.

Spatial patterns
Biophysical interactions
Human impacts
Management practices

Sandra Salamacha

Philip Jones

Aino Kay

Tweed Heads High School

Duval High School

Orara High School


The student:


explains the changing nature, spatial patterns and interaction of ecosystems, urban places and economic activity


explains the factors which place ecosystems at risk and the reasons for their protection


evaluates environmental management strategies in terms of ecological sustainability


evaluates the impacts of, and responses of people to, environmental change


applies maps, graphs and statistics, photographs and fieldwork to analyse and integrate data in geographical contexts


explains geographical patterns, processes and future trends through appropriate case studies and illustrative examples


communicates complex geographical information, ideas and issues effectively, using appropriate written and/or oral, cartographic and graphic forms

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Ha Long Bay, Vietnam, is a geographical investigation of the functioning of an ecosystem at risk, its management and protection. It is a case study of a coastal ecosystem but includes other operating ecosystems including intertidal wetlands, mangroves, coral reefs and marine ecosystems.

Further extensive information of Ha Long Bay from the World Heritage Website (external website)

Map of Ha Long Bay (external website)

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Spatial Patterns

Ha Long Bay is situated in northern Vietnam within the Quang Ninh Province, approximately 165 kilometres east of Hanoi. Ha Long Bay is on the western coast of the Bac Bo (Tonkin) Gulf, with a latitude of 21 degrees north and a longitude of 107 degrees east and it covers an area of approximately 1500 square kilometres.

Ha Long Bay using a number of different maps (external website)

A satellite image of Ha Long Bay (external website)

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Biophysical Interactions

Weather and climate

The climate of the Ha Long Bay area is dominated by two monsoon periods -

The annual rainfall averages between 1800 – 2000 millimetres.

The summer monsoon temperature ranges from 25 – 29 degrees celsius whilst the cooler/dryer monsoon temperature ranges from 15 – 23 degrees celsius. The humidity of Ha Long Bay averages 75-90%.

Geomorphic processes

The word Ha Long in Vietnamese means “dragon descending”. Legend has it that when Vietnam was threatened with invasion centuries ago, the Jade Emperor sent down a mother dragon and her children to help fight the invaders. As they descended, the dragons spat out innumerable pearls, which were changed into jade stone islands.

Stone islands of Ha Long Bay
Stone islands of Ha Long Bay

The larger rocky islands where the dragon landed were called Ha Long, the smaller islands, Bay Too Long after the dragon’s children, and the long string of islands Long Vi (now the Tar Co peninsula), where the dragons’ tails wriggled.

The landscape of Ha Long Bay is North Vietnam’s oldest. Periods of climatic change over millions of years have resulted in great undulations in the region. Ancient rivers have gauged out pathways across the plain. These ancient riverbeds remain and form the shipping routes through Ha Long Bay (the bay is otherwise quite shallow for large shipping).

The result is the spectacular landform of the Bac Ba Gulf archipelago within Ha Long Bay, with over 1960 stone islands of various sizes rising from a drowned plain.

Most of the islands of Ha Long Bay are concentrated in the Hon Gai Bay and the schist island in Cam Pha Bay. Larger islands (eg. Ruan Chau, Hgoc Vung, Hon Reu) are inhabited by people and wildlife.

Many islands contain caves and grottoes. Such an area is known as karst topography.

A cave of Ha Long Bay
A cave of Ha Long Bay

Hydrologic and pedologic processes

Ha Long Bay’s catchment area totals 105 000 hectares.

There are 5 main rivers:

Ha Long Bay is actually fairly shallow with depths adjacent to the coastline between 1.0–1.5 metres. The bay deepens slightly to the south with depths of two metres. There are channels, which have depths up to twenty metres, however, they are narrow and are used as shipping lanes. Overall, the shallowness of Ha Long Bay means it has a high potential for eutrophication.

Eutrophication - high nutrient levels from run-off supports a dense plant population that kills aquatic life by depriving it of oxygen.

Ha Long Bay’s salt content is between 23-35.5%, which is quite high compared to other Vietnamese waters and the tidal range is high but the many islands act as buffers to the waves so the bay is extremely calm with little wave action.

Fine grain sediment covers the seabed, with sand expanses around some islands, allowing for the establishment of mangrove vegetation. The coastal area of the bay displays tidal flats and hills of terrigenous rock of the Mesozoic era.

In Ha Long Bay, relatively stable sea levels over the past 5000 years have enabled the development of beaches. Sands found on the limestone islands are shelly whilst coastal/bay side sand is terrigenous. Tidal flats are covered with pelitic mud.

There are ten soil types in North Vietnam and three of these (saline, acid sulphate, degraded) are problematic and exist in the Ha Long Bay area.

Biological value

Ha Long Bay is a unique ecosystem. The area contains many different land (terrestrial) and sea (marine) species of flora and fauna, some of which are endangered. The unique combination of species forms an intricate web of interrelationships in Ha Long Bay.

The marine ecosystem

Many of the species of marine life unique to Ha Long Bay are located in the calm and warm waters of the bay. These waters are protected from the South China Sea by the limestone islands of the bay. The maritime and climatic conditions along with a favourable food supply allow certain species of fish to remain in Ha Long Bay all year long, providing a consistent catch for the locals and a food supply for larger predatory fish species higher up on the food chain. Important habitats for fish are mangroves, sand/mud bottom zones, rocky and coral reefs and bay areas. Each habitat has typical species. Drifting fish have 3 major spawning areas: Cua Luc, Dau Be, Tuan Chau. Bottom dwelling fish spawn in coral reefs and nearby waters. Larger snapper and groper spawn in Bgoc Vun and Cong Do. Large species of fish, which generally live offshore, are found in Ha Long Bay due to the favourable shelter provided by the bases of the islands. The steep almost vertical drop of the islands, the depth of the water close to the islands, the shadows cast by the islands and the numerous underwater caves allow a safe habitat for normally deep sea, offshore dwelling, wild game fish.

Quang Ninh Sea Products estimate a total of over 1000 species of fish live in Ha Long Bay.

Along with many species of fish estimated to live in the bay are crustaceans including shrimp (including sea shrimp, lobster and crayfish), squid (including cuttle-fish) and sea crabs.

Shrimp (prawns) are in abundance in Ha Long Bay, and are harvested by locals using traditional methods or by trawlers using high tech equipment. The onset of the North East monsoon drives the offshore dwelling prawns into the bay to feed and lay eggs. Squid also enter the bay and trawlers using modern methods can harvest many tonnes.

Pearl oysters are also native to the bay, as are many species of coral (both branch and fan varieties). Algae and sea grasses provide food and shelter to other marine species.

Wetland ecosystems

There is 32500 hectares of wetland in Ha Long Bay including mangrove wetlands [357ha], low tidal mud flats [3109ha], beaches [24ha], and salt lakes [40ha]. Wetlands are spread widely along Ha Long Bay due to the mild slope of the land and the high tidal range. The waters off the wetlands are shallow, averaging less than 20 metres in depth.

a) Mangroves

There are 13 species of mangroves identified in Ha Long Bay with Aegiceras corniculatum, Kandelia candel and Avecinnia marina dominating.

The Department of Agriculture and Rural Development of Quang Ninh Province has recorded a significant drop in mangrove swamps since 1972 due to reclamation and dyke construction for aquaculture.

Areas favourable to mangrove formation include

Mangroves vary in size from six metres to 0.8 metres depending on species and growing conditions.

Mangroves play an important role in marine ecosystems by providing breeding and nursery grounds for fish as well as protecting coasts from erosion. The damage that has been done through reclamation and aquaculture is severe and noted by environmentalists in the Province. As a result the Province has established support for reclamation projects through the Red Cross.

  1. Flora and Fauna in Mangrove Swamps and Tidal Flats.

    Fish are divided into two groups: resident or migratory. Resident fish, including the goby, inhabit holes in the bottom of the mangrove canopy or under stones whilst migratory fish live in the water layers, which move into the mangrove areas on high tide and recede on the ebb tide.

    Crustaceans and molluscs (shellfish) are found in both the mangroves and tidal flats. Some, such as the mud crab, shrimp and clams have high economic value.
  2. Seagrass

    There are six species of seagrass remaining in Ha Long Bay. Prior to 1970, seagrass beds were more extensive – particularly near the Dua Go cave and Tuan Cho Island.
  3. Coral Reefs

    The 160 varieties of coral are limited to the southern area of Ha Long Bay, with the number of taxon and living coral coverage increasing offshore. There are both hard and soft corals with living coral cover. Some reefs are now dead or in poor condition. Most corals are to be found at a depth of 2-4 metres. Total coral reefs cover approximately 120 hectares of Ha Long Bay. Due to mud bottoms and high turbidity there are no coral reefs near Hong Gai or Bay Shays, or islands close to those towns.
  4. Plankton

    The phytoplankton’s are common to most coast and sub-tropical waters of Ha Long Bay. 166 species of 6-phytoplankton phyla have been identified.
  5. Salt marshes

    Salt marshes occur on the landward side of the intertidal zone. There is also a boundary on the bay side, consisting of a fringe of she-oaks, mangroves and rushes. There are exposed bare patches of mud, covered in salt during the dry season and algae during the rainy season.

    Spiders and insects inhabit this ecosystem along with mosquitoes, which breed in the puddles. Estuarine fish visit and feed off the insects. Crabs find shelter burrowing into mud or under logs, along with slaters, snails and slugs.

    Surface run-off is estimated at 980 million-m/3 year (30m3/s) and 60% of this run-off occurs from June to August. Water quality and stratification in Ha Long Bay is influenced by river discharge.

    Removal of vegetation from the hinterland (for housing, logging, coal mining, limestone mining) has lead to an increase in the sedimentation load carried into Ha Long Bay.

    Increased nutrient loads also enter the Bay via the hydrological cycle.

Natural Stress

Storm surges and cyclones occur with the commencement of the west monsoon when sudden and heavy downpours flush out dry river and creek beds. As a result, there is a rapid increase in suspended particles, which wash down the rivers in Ha Long Bay, leading to increased turbidity and a lack of water clarity. Intertidal wetlands have a reduction in brackish water due to increased freshwater flow. This temporarily affects mangrove species, which rely on brackish or high salt content water. Equilibrium is restored as stream flows decrease.

Resident fish in the bottom of mangrove canopies, which live in water layers, and move in and out of mangrove areas, are affected by changes in tidal patterns. The surges of floodwater from the hinterland destroy some fish habitats and make it difficult for migratory fish to return to mangrove areas. Increased suspended particle levels in areas of excess water flow will temporarily change the feeding patterns of fish and shellfish. An increase in nutrient levels will benefit some grazing species of fish through weed growth.

Salt marshes have bare mud patches that are normally encrusted with salt in the dry monsoon season. During flooding, the extra freshwater dissolves the crystals, and is replaced by fine green algae. Consequently, there is an increase in salt marsh snail populations as the snails feed off and breed within the algae.

Cyclone and storm surges often have a temporary detrimental effect on seagrass beds, with many entire plants being uprooted and washed away. These, however, decompose to become detritus in mangrove zones.

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Human Impacts

Human Impacts – a diagrammatic summary

Human Impacts – a diagrammatic summary

Sea Gypsies

The island ecosystems have remained relatively unchanged until recently as the original “island inhabitants” were basically sea dwelling gypsies. ‘Sea gypsies’ lived on Ha Long Bay in small wooden boats that acted as transportation, a means to extract a living, and living quarters. ‘Sea gypsies’ traditionally gather marine organisms such as fish, mussels and other shellfish and oysters, principally for their own consumption. The sea gypsies found little if any use for coral in the past, and did not over-fish. Their nomadic lifestyle suggested an intricate understanding of ecosystem functioning and the need to conserve and leave environments intact.

Today, the sea gypsies live in sheltered waters of Ha Long Bay, periodically coming ashore on the mainland to trade for goods unobtainable through their lifestyle.

However, their rate of cultural change has now rapidly accelerated through the growth of tourism coupled with an increasing standard of living. The sea gypsies have become commercial in their activities. They now sell their marine products to people from the mainland. The sea gypsies harvest crabs, shells, shellfish and coral to sell to tourists, typically approaching tourist boats in their boats and ‘hawking’ their products. They often act as tourist guides, hiring their small boats to tourists from larger vessels, providing access to places such as grottoes in the islands accessible only through small portals.

Coral Sellers of Ha Long Bay

Coral Sellers of Ha Long Bay Coral Sellers of Ha Long Bay

“When the sea is calm and has receded, coral collectors boat out to the bay’s surface to work. They drop anchor in the sea area with coral, then in turn dive to the bottom of the sea to pick branch by branch, fan by fan, to keep them from being damaged. Divers emerge on the surface and give a signal to people on the boat to pull up the basket full of coral. Coral is then soaked in a basin of limewater to clean its bowels. After three months, the coral is dried in the blazing sun and turns from blue white or brick red into dark red. Artists choose coral branches and fans to create strange and beautiful bunches or baskets of flowers.”

‘Ha Long Bay - World Heritage’, published by the Management Department of Ha Long Bay.


With an increasing tourist trade, mangroves and seagrass beds have had to be cleared and jetties and wharves have been built for tourist boats.

Fuel and oil, along with tourist litter, have created pollution problems, which impact on both the aquatic and terrestrial ecosystem of the islands. Human waste from portable toilets erected for tourists, finds its way into the soil and water surrounding the islands, once more altering the ecosystem functioning through increased nutrient flow.

Tourist resorts of Ha Long Bay
Tourist resorts of Ha Long Bay

Game fishing, often near coral reefs are threatening many endangered species of fish. Often the fish is not consumed locally but exported to other markets around the region.

The delicate limestone cave ecosystems are diminishing as tourists visiting the caves break off stalagmites and stalactites. Litter, including wine bottles, is dropped into cave streams and visitors exhale carbon dioxide, which has a deleterious affect on the caves. The mouths of some caves have been widened to allow tourist access. This increase in light has lead to an imbalance in the delicate links between the flora and fauna, and a decrease in the humidity of the caves.

Cat Bah Island

Cat Bah Island is one of the largest islands in Ha Long Bay and is home to at least five different terrestrial ecosystems. National Park authorities have endeavoured to maintain these ecosystems, though with difficulty. Local villagers who have lost their traditional lifestyles are cleaning National Park land and hunting in the rainforests. Some species of fauna hunted are endangered and not necessarily for local consumption. Various exotic birds and monkeys are sold illegally to individuals overseas who desire them as pets or exhibits.


The area of Ha Long Bay is an increasingly important shipping route.

Coal barges, fuel vessels and general cargo ships are a regular sight in the bay and represent an important economic activity for the area, allowing for the export of coal and bringing in the supplies needed by the people of the province. Trading activities have taken on a renewed interest since the introduction of the Doi Moi policy, ( freer trading and business activities ). The bay is very shallow in parts and shipping accidents occur as larger vessels navigate the bay.

Coal Ship
Coal Ship

In terms of Ha Long Bay, shipping accidents take the following three forms:

The main ports in the Ha Long City system include the:

Quang Ning Port – a coal port owned by VINACOAL; an oil port, owned by Petrolimex and the Cai Lan Port, owned by the Vietnam Maritime Corporation. Cai Lan is the largest deep-seaport in northern Vietnam and has the advantages of being situated out-of-the-wind and secure. The Japanese Coastal Project Development Institute (OCDI) and Nippon Koei Colt together with the Vietnamese Transport Survey and Design Company (TEDI) are undertaking the expansion of the port.

Fishing Industry

In this area of the bay the fishing profession is ancient and practices traditional methods of fishing, the number of fishermen has been estimated to be close to 45 000. Old junks (fishing boats) can still be seen in the bay and the fishing nomads still have their water villages in those coves, which are more sheltered and secluded. Many of the traditional fishermen regard the fish resources of the bay as common property and their aim is to maximise their catch and this is often at the expense of the bay ecosystem and without regard to the concept of ecologically sustainable use.

The number of people thought to be living this lifestyle of fishing nomads is about 3000, some of who concentrate near Hong Gai because it is close to the Hong Gai fish markets.

Fishing in Ha Long Bay
Fishing in Ha Long Bay


Fishing ponds have been built and cover up to 14 000 hectares in total. These ponds are used to breed fish as well as shrimps, oysters and clams. Fish can be seen growing on rafts in Ha Long Bay. The fish products are sold at the local fish markets and to restaurants.


Human induced change is evident on the mainland with changes to shoreline terrestrial and aquatic ecosystems including seagrass, mangroves, and intertidal wetlands.

Natural ecosystems have been cleared intentionally for various agricultural purposes, urban development (new housing), industrial developments, such as coal mining, and commercial development including tourist hotels and theme parks.

New road developments Ha Long Bay
New road developments Ha Long Bay

These intentional changes have led to significant damage to marine and wetland ecosystems through saltation, industrial pollution, raw sewerage outfalls and non-biodegradable debris (local rubbish, tourist and hospital refuse).

Land reclamation for tourist purposes (hotels, theme parks, beaches), local housing, roads, and coal loading facilities has meant that thousands of hectares of mangrove and wetland areas have disappeared completely.

Of increasing local significance to the economy is aquaculture. Pollutants from urban areas and agricultural waste have increased nutrient levels, heavy metals and organic materials in the water of Ha Long Bay. Oxygen levels in the water have been reduced due to excessive weed growth from the organic matter and nutrients. Reductions of oxygen levels adversely affect oxygen-consuming organisms.

Increased atmospheric pollution from vehicle emissions and suspended coal dust particles affect both the flora and fauna of terrestrial ecosystems at a local level by harming plant species, on which many insects depend and humans in terms of lung diseases.

The massive reduction of mangrove species in Ha Long Bay has meant the absolute destruction of some wetland areas, and the modifications/adaptations in breeding /nursery grounds for many species of fish. Local fishers have reported dramatic declines in fish numbers.

Heavy metals

With little capacity in Vietnam to test for the presence of heavy metal pollution, the exact degree of this problem is not yet known. However, it is known that coal mining close to Ha Long Bay, transportation, industry, especially in nearby Haiphong, and agricultural practices, including artificial fertiliser production and use, release heavy metals into the environment, especially if stringent control measures are not in place. These three activities all occur in close proximity to Ha Long Bay, so it is fair to assume that such pollution is, and will increasingly affect, the marine and terrestrial ecosystems of Ha Long Bay.

Coal Loader – Ha Long Bay

Coal Loader – Ha Long Bay Coal Loader – Ha Long Bay

Heavy metals of concern include cadmium, lead, mercury and arsenic. Cadmium is of particular concern, as it is easily spread from polluting sources.

Agricultural Waste

Pollution by organochloride pesticide residues has been identified in Ha Long Bay. Samples taken in 1994 - 1996 found HCB, Lindane, DDD, DDE and DDT residues in Bay water and sediments, as well as in the tissue of mussels.

Whilst the residues in water were 10 - 100 times lower than the ‘permitted limit’, in mussels they were 50 - 1000 times higher due to the concentration and accumulation of the residue by such organisms. Notably, levels were considerably higher in the wet season.

The increasing use of artificial fertilisers in agricultural activities around Ha Long Bay results in an increasing problem from these pollutants.

Coal Mining

Impact of coal mining on Ha Long Bay

Impact of coal mining on Ha Long Bay

The impact of coal mining, its processing and transport is highly visible in the Ha Long Bay area, where the coal town of Hon Gai, or Ha Long City is located. The coal basin centred here has 2.9 billion tonnes of potential supply but usable reserves total about 2.5 billion tonnes. The basin is greater than 130 kilometres in length and between 10 to 30 kilometres wide covering an area of some 1300sq.kilometres. The industry has developed over 100 years, with the various French companies having operated in the area since 1888. This area is the biggest coal mining area in Vietnam with about 94% of the coal being produced here. In this area the coal mining operations are undertaken by the Vietnam National Coal Corporation ( VINACOAL ) which was established in 1994 to manage both the coal production and its marketing. VINACOAL is the largest employer in the province of Quang Ninh where Ha Long Bay is situated. VINACOAL supplies 90% of all coal consumed domestically (coal reserves provide the energy sources to drive industrialisation and urbanisation ) and provides 100% of the exported coal.

VINACOAL operations – Ha Long Bay

VINACOAL operations – Ha Long Bay

Concentration of the population in the coastal areas of Haiphong to Ha Long is directly attributable to the areas coal mining activities. Ha Long City population is approximately 142 000 and is predicted to grow to 280 000 by the year 2010. Many of these people will work for VINACOAL in the extraction, transport and processing of the coal. Most of the coal is extracted through open-pit coalmines.

At the production plant, human labour is still used to sort and grade the coal rejected by the newly installed equipment (purchased from Australia).

In recent years, open cut mines have started to undertake revegetation of the areas no longer used, including the slopes adjacent to the mines. Since 1999, this has been managed by an environmental protection authority funded by Vietnam Coal Corporation (VINACOAL).

The environmental protection authority also monitors other constraints on the operations of mines in Vietnam such as:

  1. the Decree Law on Mineral resources (1989), which states with regard to the operators in the mining industry that they conduct activities using technologies, equipment, and materials that are environmentally sound and that they must cover all the cost for rehabilitation of the environment

  2. the Law on Environmental Protection specifies that mine operators must use non-polluting techniques, rehabilitate and reclaim the land and surrounding environment during and after completion of mining activities.
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Management Practices

Ha Long Bay falls under the following jurisdictions:

Administrative level



Ministry of Science, Technology & Environment


People’s Committee of Quang Ninh Province

Sub - provincial

The Management Department of Ha Long Bay

The organisation most responsible for the daily administration of Ha Long Bay is the Ha Long Bay Management Department. This authority is under the control of the Provincial People’s Committee, the equivalent of Australian state governments.

The Management Department has the task of reaching compromises between the National Government and the Provincial People’s Committee (PPC). The PPC is keen to raise the living standards of the population and the economic development of the region, including the lucrative tourism industry, whilst balancing such attitudes against environmental protection for Ha Long Bay. The PPC collaborates with UNESCO, the UN authority responsible for World Heritage nomination and management.

The Management Department has put in place a Management Plan for the future development of Ha Long Bay.

In developing plans and monitoring environmental impacts, the Management Department is reliant on assistance from organisations outside Vietnam. For example, the World Bank assisted with a Report entitled “Options for Comprehensive Development of the Quang Ninh and Hai Phong Coastal Region” whilst the Japanese International Cooperation Agency sponsored and assisted with a major summary entitled “The Study on Environmental Management for Ha Long Bay”. It is predominately through reports including the aforementioned that the management department outlines their plans.

The Study on Environmental Management for Ha Long Bay. It is, however, unlikely that the local, provincial and national governments in Vietnam will allocate such a large sum of money to this area in the immediate future. Some of the projects may occur with injections of foreign capital, joint ventures or government grants.

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  1. Explain the biophysical interactions of Ha Long Bay (H1, H12)
  2. What has been the impact on Ha Long Bay of human induced changes? (H2, H10)
  3. To what extent have the management practices of Ha Long Bay ensured the sustainability of the ecosystem? (H5, H6, H8, H9)
  4. Compare the biophysical interactions of Ha Long Bay with that of Minnamurra Rainforest and outline the reasons for the diversity (H1, H10, H12)
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