Indus River Delta–Arabian Sea mangroves

The Indus River Delta-Arabian Sea mangroves are a large mangrove ecoregion on the Arabian Sea coast of India and Pakistan.

Location and description

These mangroves are found in the Indus River Delta on the Arabian sea, an even saltier estuary than usual due to the salts brought to the coast by the Indus from the Thar Desert, a process that is ongoing as the river is increasingly used for irrigation and water supply. Mangroves are an important habitat where salt and fresh water mix and support a range of plants specialised to survive in this salty environment, and large numbers of fishes and crustaceans that find food, shelter and oxygen in the waters beneath the tree roots. The climate is hot. The Indus River is used extensively for irrigation and by the time it reaches the delta, the flow of freshwater is down by more than 90% compared to historic levels. Active flow only lasts for about two months, and the sediment load is similarly diminished. Saline water intrudes upstream for about 80 km (50 mi) and this affects both the mangroves growing in the area and the agricultural land. Loss of sediment causes increased coastal erosion, and this is exacerbated by land subsidence and rising sea levels. Other factors affecting the mangrove areas are pollution from sewage and industrial effluent, and parts of the mangrove area have been lost to agriculture and urban development.

Flora

Mangroves forests have a thick canopy and an undergrowth mainly of saplings of the mangrove trees.

Fauna

The mangroves are especially important as a sheltered haven where fish, crustaceans and invertebrates can reproduce. They are also home to large numbers of seabirds. Mammals of the delta include fishing cats.

Threats and preservation

Pollution from the industrial city and port of Karachi is a threat to habitats in the delta, as is depletion of the Indus as water is extracted. Most of the Indus delta mangroves have been cleared for firewood and to create grazing land but some remains in three protected areas: Marho Kotri, Cut Munarki Chach Wildlife Sanctuaries and Mirpur Sakro Game Reserve.

In projects started in 1985, the Sindh Forest Department has been in the forefront of replanting and restoring mangrove areas in the delta, with support from the International Union for Conservation of Nature, the United Nations Environmental Programme, UNESCO and the World Bank. About 160 square kilometres (62 sq mi) of grey mangrove (Avicennia marina) and red mangrove (Rhizophora mucronata) have been established and a further 30 square kilometres (12 sq mi) of red mangrove restored.