Critical Habitat Information System (CHIS) on Kadmat Island, Lakshadweep
14 June, 2012 Kochi
Marine ecosystems of the Lakshadweep island are unique and known to have very high degree of biodiversity and a number of endemic flora and fauna. Coral reef of these islands is known to have the richest biodiversity in the entire Indian sub-continent.
Critical Habitat Information System (CHIS) Kadmat
Report on Kadmat Island Lakshadweep, published by Indian Coast Guard, Ministry of Defence, Government of India
Critical habitats are identified as areas, which are vital to the survival of the species at some phase of its life cycle or to the survival of the community, because of the ecological processes, which occur within it (IUCN, 1976). Critical habitats include feeding, nesting, breeding and nursery areas of estuarine and marine animals; major sources of food and nutrients for feeding areas elsewhere (e.g. mangroves); or areas that are particularly rich in species (e.g. coral reef); or highly productive areas (e.g. seagrass); or areas of special scientific interest.
Integrated Coastal and Marine Area Management (ICMAM), Project Directorate has initiated a World Bank funded programme for capacity building in essential areas of ICMAM which encompasses the use of modern tools and techniques like remote sensing and GIS for management of critical habitats. Under this programme, a Critical Habitat Information System (CHIS) using GIS facilitating study of management and monitoring of eleven critical habitats distributed in the east and west coast of India is under preparation. One of the areas chosen is Kadmat Island of Lakshadweep.
Marine ecosystems of the Lakshadweep island are unique and known to have very high degree of biodiversity and a number of endemic flora and fauna. Coral reef of these islands is known to have the richest biodiversity in the entire Indian sub-continent. During the past few decades, there has been rapid development in these islands, which has resulted in the degradation of coral colonies on the reef flats as well as in the lagoon, leading to a notable decline in their biodiversity.
The major objective of this study is to create an Information System on the resources of the Kadmat island using Geographical Information System, incorporating components of Remote Sensing and an external database. This would help the decision makers in effectively monitoring and managing the biological wealth of this area.
The Information System has been developed by the ICMAM Project Directorate using information from a variety of sources. The primary data on biodiversity have been collected under the Project “Development of GIS for Critical Habitats” by the National Institute of Oceanography, Goa. The data on fish catch and socio-economics have been provided by the Directorate of Fisheries, Lakshadweep Administration.
Kadmat island one among the Lakshadweep group of islands in Amini Taluk is located between 11o 15’ 52” N – 11o 15’ 26” N and 72o 45’ 41” E – 72o 47’ 29” E. The island stretching North to South is 8 km long, 0.5 km wide and has an area of about 3.12 sq. km. The island has a human population of 3985 (1991 census), approximately 1277 persons/sq. km. Fishing is the main occupation of the islanders.
Based on the ecological and economic value of this island, the Ministry of Environment and Forests and Union Territory of Lakshadweep Government have declared it as a marine protected area for preservation of these habitats and their resources.
Major habitats of Kadmat island Kadmat island has three types of habitats namely coral reef, seagrass and nesting ground for marine turtles. Such habitats are found in about one third of all shallow coastal waters in the tropics and Kadmat is no exception. All three ecosystems are of major importance and are closely interconnected through hydrodynamic circulation pattern and tropic system.
Coral reef The reef zonation of the Kadmat island has reef flat, reef slope and lagoon. Fringing reefs are adjacent to the shorelines and act as spawning and nursery grounds for a large number of fin and shell fishes (Fig. 2). Kadmat reef has a high diversity with a total of 45 species of corals recorded during 1986 (Pillai and Jasmin 1989). The reef of the Kadmat island is now under severe threats due to natural and man-made activities.
Fringing reefs are found mostly within and bordering the lagoon. They occur at a distance of 300- 500 m from the shore and mostly within 5 m depth. Patch reef are found scattered in the Northwestern part of the lagoon.
The seagrass beds are important feeding grounds especially for a number of threatened marine species including turtles and dugongs. They are also important spawning and nursery areas for many species. Seagrass beds are stablising the coastal sediment, substrate and provide vital oxygen to surrounding water masses. The animals like fish which live in these habitats provide an important source of food for coastal and island population. In India 14 species of seagrass were recorded of which 7 species were found in the Lakshadweep group of islands.In Kadmat island, two species of seagrass i.e. Thalassia hemprichii and Cymodocea rotundata have been observed.
The island of Kadmat is identified as one of the most important nesting and breeding grounds for marine turtles. In the Indian coastal waters, five species of sea turtles are known to occur. Of these, four species are found in Kadmat island. They are Chelonia mydas(Fig. 4), Eretmochelys imbricata, Lepidochelys olivacea and Dermochelys coriacea
Turtle nesting grounds were identified in three places in Kadmat island. They are South Western side of lagoon beach area, South Eastern side of seaward beach area and Northern end of the island. The nesting is mostly observed during the pre-monsoon period (March-April).
Geomorphology of the Kadmat island
Kadmat island is spindle shaped, broadest in the middle tapering towards the narrow strip at the southern end. The island does not show any major topographic features but is largely low leveled flat tapped and generally rising to a height of a 2-3 metres above sea level. The geomorphology of the island is shown in Fig. 6. The features associated with the island are reef flat, reef slope, lagoon, sandy beach, island vegetation, etc. The lagoon is quite large and deep along the western side of the island with a narrow beach along the eastern side. The lagoon side of the shore is sandy beach, though at places, beach rock is exposed at the low tide mark. The depth of the lagoon varies from 2 to 3 m. The reef flat is about 50 m width and is totally exposed during the low tide. During the high tide, water exchange takes place between the lagoon and the open sea over the reef.
Indian marine fisheries are multi-gear and multi-species in nature with diverse fishing practices. Trawl nets and pole line are the principal gears operated in the Kadmat island. The major economic activity of the Kadmat Island community is oceanic tuna fishing. Reef fishes have traditionally been exploited to a very low subsistence level. The lagoon and reef patch fisheries are extremely important to the survival of the islanders, since they provide them with a safety blanket for food security during the monsoon season. During this season, the fishermen are not able to venture into the open sea. The fishermen use locally made wooden craft for fishing. The chief fisheries comprise sharks, rays, tuna, skipjack tuna, perches, carangids, sail fishes, rainbow sardine and cephalopods. The tuna pole and line fishery at present is carried out in a narrow belt around the island. The marine fish catch from Kadmat island during 1991-95 ranged from 107 tonnes to 300 tonnes. Table 7 and 8 give the quantum of fish landed during 1999 and 2000 at the Kadmat island. Fresh tuna caught is processed in the canning factory at Minicoy. Otherwise the fishermen dry the tuna in the sun after cooking and smoking. The resultant product is known as “Mas”, the value of which on an average is Rs.75 – 100/kg during 1998. Fish aggregating devices known as “Papan” were introduced in Lakshadweep, which appears to have increased the fish catch.
According to Census 1991, Kadmat island has a total population of 3,985 consisting of 2032 males and 1953 females. The population density per sq. km. is 1227 nos. Malayalam is the predominant language spoken by the people. The attitude of people towards literacy and education has been recorded to be positive and hence the literacy rate is very high (85%). The educational facilities comprise three nursery schools, three junior basic schools, a senior basic school and a college. For higher education, the students have to come to the main land. Education for girls is highly encouraged and totally free of cost.
The main occupation is fishing, coconut cultivation and coir twining (Fig 11a,b & c). 230 persons are involved in fishing and allied activities. There are about 10 mechanised boats, 15 country wooden boats and various kinds of gears such as long line, hook, trawl net and shore seine are used for fishing. Four cooperative societies are functioning and they provide rice, kerosene and other commodities to the island people. Main source of income is from tuna fishing and coconut cultivation.The per capita income of fishermen is about Rs.3460/month.
Causes for degradation of coral reef In general, major threats to coral reef are human pressure in coastal areas, which have immediate localised impacts and natural pressure, particularly those related to global climate change. It has been estimated that 10% of all coral reefs have been irretrievably damaged and that a much greater percentage is threatened. (IUCN 1976). The causes of critical habitat degradation are aggregate extraction and dredging, coastal reclamation, over-exploitation of biological resources and unplanned tourism activities. The natural pressures are cyclones, coral bleaching, coral disease, predation of “crown of thorns” global change etc. In Kadmat Island, the following activities appear to pose a major threat to coral reef as well as seagrass habitats.
The main entrance to Kadmat is dredged (Fig. 12) and the dredged materials are dumped into the lagoon resulting in increased sedimentation and consequent high mortality of corals. The dead corals disintegrate and are covered by growth of algae. Due to the absence of corals, the number of fish and invertebrate species has declined.
Coral blocks and coral sand mining The sand along the beaches consists of white coral sand, produced by crushing coral blocks of the sub-littoral areas by wave action and transported on to the beach. The mining of coral blocks (Fig. 13) in Kadmat beach is being done for many years for constructing houses (Fig. 14), fences and producing quicklime. The total amount of coral blocks mined has not been estimated, but it may be that a great amount of coral blocks has been removed from the coral flats and they may affect the changes of geomorphology of islands.The coral mining has resulted in slow death of the reef and decrease in sources of the coral sand to the beach. The coral sand mining has resulted in increase of shore erosion.
Extensive coral reef bleaching appears to have occurred during abnormal seawater warming during 1998. There was an increase of about 1 to 3oc above the normal temperature of seawater in summer season. It is estimated that 95 – 98% of corals were bleached. Line transect assessment in some reef sites showed decrease in several coral community components after bleaching event. According to Pillai and Jasmin (1986), 45 species of live corals were observed during 1986. However, after the bleaching effect only 9 species of corals were observed in the lagoon as well as reef slope area of Kadmat island. The total live coral cover, number of species, number of colonies and species diversity of other fauna have decreased
Kadmat island had experienced severe coastal disturbance over the last decade. Due to extensive excavation of rocks from the reef flats for building construction, the shorelines has altered and erosion of the beach has become prominent during South-West monsoon.
The sand in lagoon area is removed by dredging operation for improving harbours and sea channels in the Kadmat island. This activity disturbed greater or lesser degree of plumbs of fine coral particles which are carried along in suspension by currents, causing coral smothering and changes in reef and sea grass habitats. Fig 17 depicts the coral sand mining in north-eastern side of the Kadmat island.
During the past few decades there has been rapid development activities in Kadmat island. Coast development activities include building construction and road development in sand dune areas in the island. Reclamation and construction of reef or sand dunes to house sites have totally destroyed the entire area and disturbed the pattern of currents in the lagoon.
Other causes for coral reef degradation are ? Overgrowth of the calcarious green algae Halimeda invading into live coral areas affecting the growth and survival of the coral species. ? Unplanned and unregulated tourism activity in the island is also one of the important factors for degradation of critical habitats. ? Seasonal stormy weather conditions and wave surge probably cause serious damage to coral communities by shifting and over turning substrate boulders.
Suggestions for critical habitats management in Kadmat Island
Islanders make bricks out of coral shingle and use them for house and building construction. This should be reduced or banned. Conduct training and awareness programmes to island people on conservation of corals. Regulation on usage of corals and sand from the beaches and coastal waters for construction and other purposes. Dredging and underwater blasting in and around coral reef area should be prohibited/banned. Prevent dumping of coir waste materials into lagoon areas. Dredged materials should not be disposed off in the reef and lagoon areas.
The information system can be used as a baseline to conduct monitoring of biodiversity in future.Mapping of corals and seagrass using remote sensing and GIS has demonstrated that these tools can be excellently used for monitoring and management of these habitats in the Kadmat Island.
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Indian Coast Guard, Ministry of Defence, Government of India http://www.indiancoastguard.nic.in/