Mangroves, the ecological treasures of Sindh, are facing a steady decline due to government negligence, and apathy of the local people


MANGROVE forests are 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 bays of tropical areas worldwide. The vegetation is characterized by a woody formation, consisting of Avicennia marina, Ceriops tagal and Aegiceras corniculatum.

BENEFITS OF INDUS MANGROVE ECOSYSTEM: Mangrove forests are vital for healthy coastal ecosystems. The forest detritus, consisting mainly of fallen leaves and branches from the mangroves, provides nutrients for the marine environment and supports immense varieties of sea life in complex food webs associated directly through detritus or indirectly through the planktonic and epiphytic algal food chains.

Different species of shell and finfishes, use this mangrove ecosystem as feeding, breeding and nursery ground. It also provides an excellent habitat for snakes, birds and mammals. Indus delta is an important flyover for Migratory birds. During winter, millions of waterfowl, including pelicans and flamingos stop over in this delta for feeding and breeding. The mangroves also have a natural mechanism for desalination and they store fresh water in their roots.This makes them a ready source of freshwater.

Mangrove forests acts as the interface between land and sea. Mangroves help protect coastlines from erosion, storm damage, and wave action, by acting as buffers and by catching alluvial materials. Mangroves are used all over the world for timber, charcoal, firewood, pulp, tannin, lignin, and cellulose, wax production and for other use. Vast areas may also be set aside as national park.

An estimated 1,35, 000 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, tannins etc. The greatest economic importance of mangrove comes from fisheries that they harbour. The importance of mangroves to the rich marine fishery of Sindh, may be deduced from a comparison of the marine fish catch statistics of the two coastal provinces of Pakistan along with their mangrove covers and the coast line lengths. For instance, although Sindh has about half the coast line length (330 km) than that of Baluchistan (645 km).It has, however, a great wealth of mangroves (160,000 ha), about 22 times larger than that of Baluchistan (7,340 ha). The annual average catch of shrimp from Sindh coastal waters is 27,584 tons, about 35 times larger than that of Baluchistan (795 tons). Similarly, finfish harvest in the coastal waters of Sindh (231,242 tons) dominates over that of Baluchistan (103,512 tons). Studies have shown that the reason of this elevated productivity in the coastal waters of Sindh, is its wealth of extensive mangroves.

Mangrove themselves are used directly for fuel wood and fodder for domestic animals by the coastal villagers. Another important benefit of the Indus mangrove ecosystem, is that it protects the coast from wind and ocean currents. The Indus delta is low lying and bears full force of the southwest monsoon. It provide natural protection against cyclones and hurricanes. It has been observed that the recent devastation caused by cyclone 2A would have been minimised, had there been fully developed mangroves to act as barrier.

DESTRUCTION OF MANGROVE FORESTS: The diverse human activities in mangrove areas have lead to its loss. The major anthropogenic causes for the loss of mangrove areas are overexploitation, pollution and changes in water quality. The following phenomena contribute to these causes:

HUMAN POPULATION: The increase in 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 human settlements. Since they were regarded as wasteland, the government actually encouraged the locals to cut the mangroves down. Because of a lack of proper management, the villagers meet their fuel wood and fodder requirements by using the wood from the mangroves.

EXCESSIVE CUTTING FOR FUEL WOOD AND FODDER: Overgrazing and lopping for fuel wood and fodder has resulted in a stunting of the growth of the mangroves in many areas. Over 16,000 camels are dependent on the mangroves for their fodder requirements annually. Mangroves have also been chipped for paper production and replacement agriculture.

REDUCED FLOW OF INDUS: Mangroves require certain amount of fresh water for optimum growth, even though they are salt tolerant species. Fresh water from rivers and channels brings necessary nutrients and alluvium to mangrove forests. It also dilutes seawater, creating brackish water suitable for the growth of many species. Experiments on the growth of different species conducted in different coastal areas show that it is unusual for mangroves to grow in places lacking fresh water.

There are 17 major creeks making up the original delta, but due to reduced flow below Kotri, only the area between Hajamro and Kharak creeks now receives water from the Indus, with one main outlet to the sea, Khobar Creek. The active delta is now only 10 per cent of its original area. Consequence of the reduced volume of fresh river water flowing into the sea is the tremendous reduction in the mangroves cover from around 263,000 hectares in 1978 to about 158,500 hectares (about 40% reduction) in 1990.

Progressive reduction in fresh water flow has an effect upon the salinity in delta area (often with salinities over 45ppt). This puts stress upon mangrove ecosystem causing loss of seedlings.

MUNICIPAL AND INDUSTRIAL WASTE: According to EPA report, Karachi generates approximately 280 million gallon per day of Domestic and Industrial waste. Some of this finds its way into sea.

These discharges contain various pollutants, which originate from different sources like steel mills, refineries, power stations, tanneries, textile mills, pharmaceutical companies and municipal waste. Among these, tanneries probably are the biggest pollutants. Tannery waste has got a high heavy metal content and comes from sources that are not too easy to control.

Domestic waste including cattle excrement and remaining residues of food, are rich in organic content, which is useful for the growth of mangroves. However, suspended solids such as polythene bags, pathogenic microorganisms, nitrogen and other toxic elements can have adverse impacts on the mangroves metabolism.

DREDGING: There are two sites on the coast of Sindhh where year round maintain dredging has to be conducted in order to create suitable depth for large ships. The first is Mannora Channel, which occupies an area of 7.17 square kilometre and is feed directly by the Arabian Sea. It is an artificial harbour and suffers from chronic siltation problems. An estimated 456000 cubic meters of silt is removed annually from the channel and dredging spoils are dumped at a distance of about 5-6 km southwest of channel mouth in the Arabian sea.

Second site is Port Qasim. It also suffers chronic Siltation problem due to regular inputs of sand and silt from Arabian Sea, to which it is directly connected. Turbidity and siltation affect mangrove ecosystems, by reducing the gaseous exchange and oxygen supply to their root system.

OIL DISCHARGE: Oil pollution in Pakistan ports, inshore waters, creeks and bays through oil tankers, cargo vessels, passenger ships, mechanised fisheries vessels trawlers, harbour craft, pleasure craft and KPT flotilla. Around 3000 to 4000 ships visit the port each year. The sources of oil pollution in Manora channel are the bilges, washings from engine rooms of vessels, discharge and leaks from bunkering points, leak and small spills occurring during loading and unloading of oil at oil piers, pipeline leakage and rupture. Some oil is brought to channel through Layri and Malir discharge.

In the open inshore and offshore waters of Karachi, oil pollution occur through large number of ships waiting to enter the Karachi Port. The Indus River also brings some degradation products of oil to the marine delta.

Oil pollution can block up the gas cavities in the pneumatophores or prop roots and cause cell suffocation due to insufficient oxygen.

Mangrove forests are a very unique and complex kind of coastal wetland. They have evolved over the centuries not only in relation to their internal systems, but also to the functioning of ecological and human systems that surround them. In other words, they are an open system, and thus, are directly related to all that is around them.

The severest environmental stress, which the mangroves on Indus are facing results from the reduction of freshwater flows down the Indus , reduced loads of silt and nutrients. Studies should be undertaken to establish the minimal escapage needs, down stream Kotri as decided in 1991 water accord. Till the finding of studies become available, no new project, including Kalabag Dam should be carried out on Indus water.

To minimize use of mangrove as fuel by local people,the Government should encourage alternative fuel uses in mangrove forest areas. Stricter governmental regulations should be enforced to protect mangroves, with the cooperation of the local people. It is important to educate local people with non-destructive economic uses of the resource. A multi -disciplinary team comprising, marine and terrestrial scientists, regional and environmental planners, local and national policy makers, should be set to carry out further studies on Indus mangrove ecosystem.