Economically mangroves are a great source of timber, poles, pilings, fodder and fuel


Dr. S M. ALAM and Dr. M.H. NAQVI
Nuclear Institute of Agriculture, Tandojam
Aug 25 - 31 , 2003




Mangroves are normally comprised of taxonomically diverse, salt-tolerant trees and other plant species, which flourish in intertidal zones of sheltered tropical shores, over wash islands, estuaries and bags of tropical zones worldwide. Mangrove, a large tropical evergreen tree generally grows on muddy tidal flats and along the lines. Mangrove forests are most abundant in the continents of tropical Asia, Africa and the islands of Pacific. They produce from their trunks aerial roots, which become embedded in the mud and form a tangled network; this serves both as a prop for the tree and as a means of aerating the root system. SUGL roots also form a base for the deposit of silt and other material carried by the tides. Some mangrove species lack prop roots but have special pores on their branching roots system for obtaining atmospheric air. The mangrove fruit is of a conical reddish-brown berry shape. Its single seed geminates inside the fruit, while it is still on the tree, forming a large primary root that quickly anchors the seedling in the mud when the fruit is dropped from the tree.

Mangrove forests are very important and useful coastline ecosystems (seashore) for people of tropical and sub-tropical region. At present time, mangrove forest distributes around 1,800 million hectares in the world. However, they are shrinking due to variation of environmental factors such as tree cutting by human beings, redemption of lands, construction for shrimp and fish culture pond, etc. A swamp forest of low to tall trees and some shrubs are commonly associated with some salt marsh herbs. Swamp forests occur along the borders of much tropical seashore, where wave action is not intense and mud and peat are deposited. Most plants of this community are halophytes that are well adapted to salt water and fluctuations of tidal level. Some have still or prop roots to help hold them on the shifting sediments and others have erect root structures that crop out above the surface. It also provides an excellent habitat for reptiles, shakes, birds and mammals.

The mangrove scenario often develops as a distinct cluster of plants. In such areas, it is zoned from open water landward in a series of different species. The landward zone species developed on sediments and peats, which are initially deposited in the seaward zone. These changes due to deposition in the swamp often extend the coast outward and form islands in shallow. quite waters. The swamps when dense also afford some protection against erosion resulting from violent storms. Thus, mangrove swamps have a significant geologic role. The mangroves also have a natural mechanism for desalination and they store fresh water in their roots. Mangroves help protect coastlines from degradation, storm damage and wave action by acting as buffers and by catching alluvial materials. Mangroves are used for timber, charcoal, firewood, pulp, tannin, lignin, and cellulose, wax production and for many other uses. In coastal areas of Pakistan, an estimated 0.15 million people depend on this ecosystem for their livelihood and harvest its natural resources for various purposes such as fishing, camel browsing, buffalo grazing and wood collection, honey collection, medicines, etc.

The development and composition of a mangrove forest depend largely on soil type, salinity ranges duration and frequency of inundation accretion of silt, strength of tides, exposure or shelter on the site, and unplanned exploitation. These factors interact in a complex manner and accordingly the distribution, zonation and succession of mangrove species are highly variable even within narrow geographical limits of the coastal areas.

Mangroves are most luxuriant and complex on the seacoasts and around the surrounding islands of many countries. From here, the diversity of the eastern species decreases towards the Red Sea and southern Japan, where only a single species may be found. Of the four characteristic families, Rhizophoraceae, which forms extensive forests, is by far the most important. Other characteristic sub-mangrove tree-forming species belong to the genera Lumnitzera, Acanthus, Hibiscus, and Scyphiphora.



The Eastern vegetation is taller and richer in diversity than its Western counterpart. All the Western genera are found in the eastern vegetation, but their species composition, zonation, and succession are different. The pioneers are species of Avicennia and Sonnerafia, the former colonizing mainly the firmer, exposed seaward side and the latter largely the soft, rich mud along sheltered river mouths. Ceriops decandra plays a similar role on the sheltered east coast estuaries of the Malaya Peninsula. Depending on soil type and tidal height, these pioneers are normally succeeded by either pure or mixed forests of various species of Bruguiera and Rhizophora, such as B, cylindrica and B. sexangula on firmer clay beyond the reach of ordinary tides behind Avicennia; B. parviflora in pure crop of mixed with R. apiculata on wetter muds flooded by normal high tides; B. gymnorhiza, often mixed with sub-mangrove species Acrostichum aureum, A. speciosum (ferns), and Oncospermum filamentosa; and Nipah fruticans (palms) farther inland on drier ground with less saline soil, R mucronata is more tolerant of sandy, firmer bottoms than R apiculata and forms tangled thickets on banks of tidal creeks and in estuaries.

The coastline of Pakistan is about 1050 km long, out of which 645 km belongs to Balochistan province and 330 km to Sindh province. Sindh's coast is covered with dense growth of mangroves in the Indus Delta, while the former has poor growth. Sindh has however, a great - h of mangroves (25 x 104 ha), about 34 times larger than that of Balochistan (7340 ha). The annual average catch of shrimp from Sindh coastal waters is about 27,584 tons about 35 times larger than that of Balochistan (795 tons). The reason for this elevated productivity in the coastal waters of Sindh, is its wealth of extensive mangroves. Salinity values of water are as high as 41 ppt as compared to a low value of 36 ppt recorded on the shelf, which may do due to intense evaporation in a very shallow habitat. Soil salinity is usually higher than water above due to exposure at the low tide. The pH remains around 8, indicating alkaline nature of sea-water. Dissolved oxygen concentration ranged between 4.0 and 5.9 ml/L. The soil is mainly muddy and organic.

Pakistan's location is unique in that it borders three major geographical regions. Asia and Central Asia are situated at the North, the Middle East to the west and the Indian subcontinent to the east. The coastal area is an arid sub-tropical desert with the coastline extending to about 1000 km. One-third of the coastline is the Province of Sindh, while the rest is in Balochistan. The average rainfall is about 100-200 mm per year, and that too is sporadic and occasional. The Indus Delta is spread over 6 x 105 hectares along the southern Arabian Sea Coast in Sindh. In addition, small pockets exist also in deltaic swamps of other small rivers, which meet the Arabian Sea in the Province of Balochistan. Mangroves thrive on a continuous supply of fresh river water, but lately due to the construction of dams, a lot of water is diverted into smaller reservoirs and irrigation canals, before it reaches the delta, thus decreasing the discharge of fresh water.

Pakistani mangroves rank sixth among the mangroves spread in about 95 countries of the world. The mangroves thrive at the mouth of the Indus the sixth largest river of the world and the Indus Delta is the fifth largest delta in the world. This delta is an important fly over for migratory birds from Siberia, and thus the mangroves are an important stop over for many winter birds.

They are the arid coast mangroves (mangroves which grow in high salinity areas with low rainfall) are spread over the largest area among the world's arid coast mangroves. The mangrove's ecosystem is dominated by a single species called Avicennia marina, which forms 96% of the total crop. There are few stands of Ceriops tagal, Bruguiera conjugata and Aegiceras corniculatum. Perhaps the most important aspect of these unassuming plants is their ability to act as physical barriers to cyclones, typhoons and hurricanes. In recent past, the cyclone to hit the coastal areas of Thatta and Badin districts would not have been so intense, if the previously present mangroves had been wiped out to make room for human development. Another important benefit of the Indus mangrove ecosystem is that it protects the coast from wind and ocean currents. The roots of mangroves trap the sediment that is brought into the sea via the flow of the Indus and its tributaries. This helps in keeping the sedimentation level of the harbour under control. With the depletion of these plants sedimentation level is increasing and is a sign of concern for the port authorities.

Plants, animals, micro-organisms and people all are part of the mangrove ecosystems. The living things rely on soil and water for sustenance and growth. Microorganism is an invisible, but an essential part of the ecosystem. They digest the dead leaves of the plants and recycle the nutrients for the mangroves as well as for other plants and animals. Fish such as sardines and palla and otha sea creatures such as crab and shrimps either live in the surrounding waters or spend a critical part of their lives here. Breeding grounds and nurseries for water fowl, fish, shrimps, snakes and other fauna, they form an essential ecosystem with perhaps more biodiversity than the rain forests. Fish and shrimps are not only of importance for the ecology but also boost Pakistan's economy through exports. Shrimps export is the major chunk of fish exports, being 70 per cent of the US$ 100 million transactions. Mangroves have also been chipped for paper production and replacement agriculture. Around 14 species of sea snakes use these mangroves as a breeding ground. During winter many species of water fowls, including pelicans and flamingos make the Indus Delta their home. Over 60 species of these birds are found in the mangroves. Some, like the king fisher, live here throughout the year.



The increase in human population has put great stress on the sustainability of the mangroves. To cater to the increasing masses, the land is cleared to make room for home" settlements. Because of lack of proper management, the villagers meet their fuel wood and fodder requirements by using the wood from the mangroves. The jackals, wolf and herd of camels may also be found on many of the islands, along with a few rodents. More fascinatingly, different species of dolphins can be seen swimming around the creeks. Coastal villagers are also a part of the ecosystem, and they use the mangrove as fuel. The dominant species in these parts, the Avicennia marina, is not as good as wood from other mangroves, however, it is still used by the local people. Their leaves especially those of the Avicennia marina make excellent fodder for animals Organizations such as IUCN (International Union for the Conservation of Nature), World Bank, Forest Department and the National Mangrove Committee of Pakistan are working for the reforestation of mangroves in coastal areas of the country. In addition to that, the studies on the mangroves are being encouraged. Three decades before, the Commission of Ecology of IUCN created a group to collect existing information on the status of mangroves globally, to be used internationally in the management, guidance and conservation of this natural resource. The focus of these programmes is to initiate a development strategy in order to save the mangroves from the hazards of human activities. There is also an emphasis on the availability of alternatives source for the villagers who are dependent on these forests for fuel and fodder.

In 1985, the Government of Pakistan initiated a program for the replanting of the mangroves. More than 10,000 hectares were planted around the Indus delta. Another 3000 hectares were restocked by Avicennia marina by assisted natural regeneration. Various species were also planted experimentally in different areas of the Indus delta and the Avicennia marina and Rhizophora mucronata were predominant among them. In 1990, a socio-economic survey was conducted to gauge the dependence of local people on these mangroves. The survey showed that more than hundred thousand people were depended on the mangroves. But, they lacked many facilities and even did not have proper drinking water. The survey also discovered that a few plants had survived in the area around their settlements.

Consequently, IUCN-Pakistan initiated a mass plantation programme of Avicennia marina and Rhizophora mucronata in the coastal villages. The purpose of the program was to establish wood lots and to create an alternative source of fuel and fodder for their animals and reduce their dependence on the inter-tidal mangrove. The villagers were given technical support to grow these plants in their own vicinity. The local villagers maintain these plantations at present. Honey was already available in the forests, but apiculture had never been used as an income generating activity. In 1992-4, IUCN and the Pak-Beekeepers Society initiated the Mangrove Honey Production Project for the villagers in the northern part of the Indus delta. This was mainly to provide an alternative source of income during the time of the year, when fishing is banned in the harbour. The project has grabbed the attention of many villagers and seems to be on the road to success.

The mangrove forests in the country play a vital role in many aspects of animal, plants and human life. Mangroves serve as nurseries for fish, shrimps, crabs and other marine life. Shrimps also use them as a breeding ground. A large proportion of coastal fish and shrimp pass at least a portion of their lives in the mangroves. They are dependent on the food chains for their sustenance and are protected by these shrubs during the fragile early period of their lives. They act as guardians of riverbanks and coastlines. The areas near the sea are secured from the harmful effects of tidal waves. Their roots collect the sediment that flows into the sea with the river and slow the water's flow, helping to protect the coastline and preventing erosion. They are extensively used as fodder and fuelwood. The water surrounding them is rich in fish, shellfish and other sea organisms, which are a rich economic source for the country.

Economically mangroves are a great source of timber, poles, pilings, fodder and fuel. The bark is used in tanning and batik industries. Some species have either food or medicinal values and for shining the teeth. The mangrove tree is a creator of land. It anchors itself on muddy shores or coral reefs, where its twisting roots collect debris and sediment in which other vegetation can settle and grow. The cutting of entire trees for obtaining wood for construction of thatched houses and other purposes by local people has also resulted in soil erosion of the mangrove habitat. Mangrove thrives best in the brackish waters of creeks, marshes and lagoons. Their seedlings may drift at sea for months before wedging and taking root on a shoal to start the formation of another island. Mangrove baks is used to a limit extent as a source of tannins and dyes. The name mangrove is also applied to other unrelated constituents of mangrove vegetation, e.g. Avicennia nitida, a bush of vervain family called black mangrove. It has been found that mangroves also act a biofilter for preventing the heavy metal pollution entering into the coastal waters. Mangroves also serve as a chemical sink for heavy metals release from industrial wastes.