Wetlands, Mangroves and Coral Reefs: Ramsar Sites and PYQs

A wetland is land that stays wet for all or part of the year, so that water, not soil or air, decides what lives there. The Ramsar Convention defines wetlands as areas of marsh, fen, peatland or water, whether natural or artificial, permanent or temporary, with water that is static or flowing, fresh, brackish or salt, including marine water whose depth at low tide does not exceed six metres. Mangroves and coral reefs are two special wetland systems of the coast, and examiners treat the three together because the questions overlap.

Why wetlands matter

Wetlands are called the kidneys of the landscape because they filter sediment and nutrients out of the water that passes through them. They are also called biological supermarkets, since their shallow, nutrient-rich water supports a dense food web. They recharge groundwater, hold flood water, trap carbon in waterlogged peat and break the force of storms before it reaches the land behind. They are among the most productive ecosystems on earth, and also among the fastest disappearing, because they are drained for farmland and built over for cities.

The Ramsar Convention

The Convention on Wetlands was signed on 2 February 1971 in the Iranian city of Ramsar, on the shore of the Caspian Sea, and came into force in 1975. It is the oldest of the modern multilateral environmental agreements and the only one devoted to a single ecosystem type. Its secretariat sits at Gland in Switzerland. India became a party on 1 October 1982, and the first two Indian sites placed on the list were Chilika Lake in Odisha and Keoladeo National Park at Bharatpur in Rajasthan, both entered in 1981. World Wetlands Day is observed on 2 February, the anniversary of the signing.

A site on the Ramsar list whose ecological character has changed, is changing or is likely to change because of pollution, human interference or other causes is put on the Montreux Record. Keoladeo National Park and Loktak Lake are the Indian sites on it. Chilika Lake was placed on the record and then removed in 2002 after a new sea mouth was opened and the lagoon recovered, the first site in Asia to be taken off in this way.

Wetlands of India worth remembering

Mangroves

Mangroves are salt-tolerant, or halophytic, trees and shrubs that grow in the intertidal zone of sheltered tropical and subtropical coasts, chiefly in deltas, estuaries and lagoons where a river brings silt to the sea. The soil there is waterlogged, saline and starved of oxygen, and mangroves have three famous adaptations to it. Pneumatophores, or breathing roots, grow upward out of the mud and take in air through pores called lenticels. Stilt or prop roots arch out of the trunk and anchor the tree in soft mud against tide and wave. Vivipary means the seed germinates while still attached to the parent plant and drops as a ready seedling, which can root before the tide carries it away. Many species also excrete surplus salt through glands on the leaves.

The Sundarbans, in the delta of the Ganga, Brahmaputra and Meghna and shared between India and Bangladesh, is the largest mangrove forest in the world. It is named after the sundari tree, it holds the only mangrove population of the Royal Bengal tiger, and the Indian part is a national park, a biosphere reserve and a World Heritage Site. Bhitarkanika in Odisha is the next largest mangrove tract in India, Pichavaram in Tamil Nadu and Coringa in Andhra Pradesh are the other well-known ones. Among the states West Bengal has the largest mangrove cover, followed by Gujarat. The International Day for the Conservation of the Mangrove Ecosystem falls on 26 July.

Coral reefs

A coral reef is built by coral polyps, tiny animals of the phylum Cnidaria that secrete a skeleton of calcium carbonate around themselves; generation upon generation of skeletons make the reef. Inside the tissue of the polyp live single-celled algae called zooxanthellae, which photosynthesise, pass food to the polyp and give the reef its colour. Because that partnership needs sunlight, reefs grow only in clear, shallow, warm sea water, roughly between 20 and 30 degrees Celsius, with normal salinity and little silt, which is why reefs are absent at river mouths. Reefs cover a very small part of the ocean floor yet shelter a large share of its species, so they are called the rainforests of the sea.

Reefs are of three forms. A fringing reef lies against the shore itself. A barrier reef runs parallel to the coast with a lagoon between, the Great Barrier Reef off Queensland in Australia being the largest. An atoll is a ring of reef around a central lagoon, formed, as Charles Darwin argued, when a volcanic island subsides while the reef around it keeps growing upward. India has four major reef areas: the Gulf of Mannar and the Gulf of Kachchh, which are fringing, the Andaman and Nicobar Islands, and Lakshadweep, which is atoll country. The Gulf of Mannar was declared India's first marine biosphere reserve.

When sea water stays too warm for too long the polyp expels its zooxanthellae, the reef loses colour and turns white. This is coral bleaching. A bleached coral is not yet dead and can recover if the stress passes, but prolonged bleaching kills it. Ocean acidification, caused by the sea absorbing carbon dioxide, makes it harder for polyps to build their calcium carbonate skeletons, and silt, sewage, trawling and reef mining finish the damage.

Protection in India

Wetlands outside forests are governed by the Wetlands (Conservation and Management) Rules, 2017, which forbid setting up industry, dumping waste and permanently converting a notified wetland. Mangroves and coral reefs are treated as ecologically sensitive areas under the coastal regulation zone notification, and both are protected inside national parks and sanctuaries under the Wild Life (Protection) Act, 1972. The National Plan for Conservation of Aquatic Ecosystems merged the older wetland and lake programmes into a single central scheme.