Development or Destruction?

"This sea is our bread and butter. Brother, if these mangroves are destroyed, the fish and prawn will go away and we will also be finished". 

(A local fisherman)

Increase in 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 them down. Because of a lack of proper management, the villagers meet their fuelwood and fodder requirements unsustainably Development has also taken its toll and industrial units such as the Steel Mill and Port Qasim have added to the threats. 

Gradual cut in the supply of Indus water

Pakistan's mangroves are common to deltas and thus need a continuous supply of fresh water from the river. The belts flourished in the past when the flow of the river was unabated and continuous. The situation is quite grave today. The construction of dams on the rivers has depleted the supply of fresh water and also reduced the amount of nutrients and silts that came with it. Perhaps the most acute problem that these plants face is the reduction in the water. While many of them including the Avicennia can survive without fresh water for long periods of time, it is unlikely that they would be able to do so indefinitely. The estimated freshwater flow from the Indus is around 150 MAF (million acre-feet) per year and carries with it some 400 million tonnes of silt. The flow is only 10 MAF today and future development envisages a complete stop of freshwater down the Kotri barrage. The silt discharge is estimated to be 100 million tonnes per year falling to about 30 million tonnes annually. 

The reduction in fresh water has increased the saline level of the coastal waters. The salinity, which is estimated to be 40-45 parts per thousand or more, is well above the normal level, conducive to the growth of marine life. This is also probably one of the causes of the extinction of species such as, rhizophora, apiculata and Sonneratia, Caseolaris, from the area. 

Excessive cutting for fuelwood and fodder

Overgrazing and lopping for fuelwood and fodder has resulted in a stunting of their growth in a many areas. These areas include islands such as Barkan Island, Hafeez Island and Muchak Island along the Karachi coast. Over 16,000 camels are dependent on the mangroves for their fodder requirements annually along the coast of Sindh. Mangroves have also been chipped for paper production and replacement agriculture. 

Pollution

Various studies show that pollution may not be directly threatening to the mangroves. The fact that mangroves are able to survive in the grossly polluted water of Karachi Harbour is indicative of their ability to survive in impure water. Pollution may not affect the mangrove plant directly, but it kills the faunal (animal) population of the sea, indirectly causing problems for the mangroves. In any case pollution in water affects the fish which we eat.

Industrial waste 

Industrial pollutants originate from different sources like steel mills, refineries, power stations, tanneries textile mills and pharmaceutical companies that have been built close to the coast and use the rivers and ocean as a dumping ground. 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.

The table below illustrates the major pollutants in the Indus delta produced by the different industries.

• Hydrochloric acid in the river has a toxic effect on the respiratory system of fish. The increased concentration of the hydrogen ion causes death by suffocation. Heavy metals especially affect the juvenile commercial shrimps. (Hydrochloric Acid Discharge: Effects on the Indus Delta - CEU - IUCNP)

• The discharges of oil from shipping and other industries impact the mangroves and the marine life. The surface layers of oil present in the water disturb the respiratory process of the mangrove trees, adversely affecting the growth and health of the plants. Even passing ships discharge oil into the water. 

• Another hazard is the 'sterilisation' of large quantities of sea - water for cooling purposes by the industries in the creek system. These thermal effects kill the larva of the sea animals, and also effects the seedlings/saplings of mangroves.

Domestic waste

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 sea life, which in turn impacts the mangroves. It is also believed that fish engulfing polythene bags die immediately