1 Department of Marine Sciences and Marine Biotechnology, (Goa University, Goa 403 206)
Abstract
Key parameters such as population size, number of houses, passenger traffic, cargo traffic and fish catch of ten major islands of the Lakshadweep archipelago are analysed to study the impact of Human activities on the reefs. Lakshadweep has the third largest population density in the country. Rapidly escalating developmental activities are largely responsible for the degradation of the reefs. Fishery resources are under-exploited and the fish catch can be augi-nented by adopting modem methods and diverting the impact of fishing boats to mainland ports. There is an urgent need to halt the degradation of reefs and reverse the trend.
Introduction
The Lakshadweep archipelago (8° N-12° 30' N, 71°E-74° E), the smallest union territory of India, is located (Fig. 1) about 220-440 kni from the mainland city of Kochii (Cochin) in Kerala. There are 36 islands (including 12 atolls, 3 reefs and 5 submerged banks) covering all area of 32 km2 with lagoons occupying about 4200 km2. They comprise the only atolls in Indian territorial waters. Of these, only eleven islands viz. Agatti, Amini, Andrott, Bangaram, Bitra, Chetlat, Kadmat, Kalpeni, Kavaratti, Kiltan and Minicoy are inhabited. Kavaratti is the administrative headquarters. A resort, catering to international and local tourists, has been set up at Bangaram to promote tourism. In addition, tourist huts have been erected at Kavaratti, Kadmat. Minicoy and recently at Agatti. The main occupation of the islanders is agriculture (coconut, Cocos nucifera) and fisheries (skipiack tuna, Katsuwomas pelamis).
During the past few decades there has been rapid development on these islands which has resulted in the degradation of coral colonies on the reef flats as well as in lagoons. Can the islands afford further developmental activities? Can the coral colonies withstand the pressure? In other words have the Lakshadweep coral reefs attained or crossed their carrying capacity? In order to analyze this problem, quantitative time series data on human activities and live coral cover are required. Unfortunately no quantitative data on coral cover are available. Qualitative changes that have occurred over the years in the environment and the biota of Lakshadweep have been described (James cl al., 1989). In the seventies, the distribution of live corals in lagoons of several islands was reported to be extensive (Pillai, 1996). It appears that the carrying capacity of the reefs was attained in the eighties. In this paper, an attempt is made to quantify and analyze human impact on the islands, relate it to the degradation of reefs and estimate the carrying capacity of the reefs.
Fig. 1. The Lakshadweep archipelago.
Key parameters
The raw data used in this study have been obtained from publications of the Department of Planning and Statistics, Kavaratti, Lakshadweep. Five key parameters are considered:
1. population size
2. number of houses
3. passenger traffic
4. cargo traffic and
5. fish catch.
Tourism has not been included as a key para-meter as its impact is limited and regulated by permits required to visit the islands.
Population size indicates the pressure exerted by exploiters (humans) on the reefs by way of exploitation of resources and sewage generated which includes defecation on the reef flats and coralline sands due to the unavailability of toilets.
The number of houses highlights the pressure exerted on reefs for construction purposes. Islanders exploit corals for construction purposes as the cost of-transporting materials from the mainland is prohibitive. It is only in the early nineties that a ban has been imposed on collection of corals for construction purposes. The magnitude of passenger and cargo traffic indicates the activities of small mechanized boats used to transport passengers/cargo from the island jetty to the vessels stationed outside the lagoon.
Lagoons have to be dredged and widened regularly to maintain the navigation passage and accomodate increasing number of boats. Incidentally, dredging in and around coral formations is not permitted under the guidelines of the Coastal Regulation Zone of the Environment protection Act (1 986). The increased sedimentation causes harm to corals. Boats also cause unintentional damage to reefs through anchor operations, etc. Fish catch data illustrate the number of fishing boats operating in the islands. The major method of fishing is the traditional pole and line method which requires live bait.
Live baits are small fishes (particularly Spratelloides delicatulus) associated with corals and are used to lure tuna. They are collected from lagoons and reefs, resulting in unintentional damage to coral colonies. Other potential living resources are not considered in this study.
It has been necessary to standardize the data to enable comparisons between islands which are of different sizes. Population size and number of houses have been converted to density values per unit km2. The decennial percentage increase in the population density and the density of houses was computed for each of the major ten inhabited islands taking 1951 as the base year. In the case of passenger and cargo traffic, the percentage increase was computed yearly taking 1980-'81 as the base year. Similarly, the yearly percentage increase in total fish landings on each island was computed taking 1980 as the base year.
Fig. 2. Percentage increase in population density in Lakshadweep islands. - Agatti
Fig. 2. Percentage increase in population density in Lakshadweep islands. - Amini
Fig. 2. Percentage increase in population density in Lakshadweep islands. - Andrott
Fig. 2. Percentage increase in population density in Lakshadweep islands. - Bitra
Fig. 2. Percentage increase in population density in Lakshadweep islands. - Chetlat
Fig. 2. Percentage increase in population density in Lakshadweep islands. - Kadmat
Fig. 2. Percentage increase in population density in Lakshadweep islands. - Kalpeni
Fig. 2. Percentage increase in population density in Lakshadweep islands. - Kavaratti
Fig. 2. Percentage increase in population density in Lakshadweep islands. - Kiltan
Fig. 2. Percentage increase in population density in Lakshadweep islands. - Minicoy
Fig. 3. Percentage increase in density of houses in Lakshadweep islands. - Agatti
Fig. 3. Percentage increase in density of houses in Lakshadweep islands. - Amini
Fig. 3. Percentage increase in density of houses in Lakshadweep islands. - Andrott
Fig. 3. Percentage increase in density of houses in Lakshadweep islands. - Bitra
Fig. 3. Percentage increase in density of houses in Lakshadweep islands. - Chetlat
Fig. 3. Percentage increase in density of houses in Lakshadweep islands. - Kadmat
Fig. 3. Percentage increase in density of houses in Lakshadweep islands. - Kalpeni
Fig. 3. Percentage increase in density of houses in Lakshadweep islands. - Kavaratti
Fig. 3. Percentage increase in density of houses in Lakshadweep islands. - Kiltan
Fig. 3. Percentage increase in density of houses in Lakshadweep islands. - Minicoy
Human impact
There has been more than a 200% rise in population density as well as density of houses (Figs 2, 3). The population density of Lakshadweep (1615/km2) ranks third in the country, next to Delhi (6352/km') and Chandigarh (5632/km'). Increase in population size will result in escalating human activities and increasing defaecation on the shores leading to the accumulation of pathogens and resulting in health hazards. Unidentified worms were observed wriggling in some wells (Rodrigues, 1996). Increased population will exert pressure on the limited land available for housing. Subsidies for transportation of construction materials could be provided. Power requirements from diesel generators will also steeply increase. Frequent power cuts are already common. The maximum increase in population density and density of houses has been recorded in Bitra, followed by Kavaratti and Agatti. Bitra is the smallest inhabited island (0.1 km2) with the largest lagoon (42 km'). In 1951 there were less than 50 inhabitants and the number has grown to 225 as per the latest census report. On this island, there is acute scarcity of freshwater which is rationed to its inhabitants. However, the region is rich in fish resources. Scarcity of freshwater is a chronic problem in most islands where groundwater instead of seawater is being desalinated. The minimum increase in population density is observed at Kalpeni, the island which boasts of intellectuals and where literacy is considered high.
There has also been a dramatic increase in passenger and cargo traffic (Figs 4, 5). The 1985-'86 and 1986-'87 data on passenger traffic appear to he incomplete. Data presented exclude passengers and cargo transported by sailing vessels (odums). The data illustrate the increased mobility of islanders and increasing cargo demands. Up to 1987-88, passenger traffic was handled by m.v. Amindivi, m.v. Bharal, Seema and m.v Dweep Sethu, besides sailing vessels. From 1988-89 onwards, a 658 capacity passenger vessel, m.v Tipu Sultan was introduced. These vessels cannot enter the shallow lagoons and hence passengers have to be transported to the jetty and vice-ierva by small mechanized boats. From January 1992 onwards, two high speed catamarans, ni.v. Khadeeja Bivi and m.v Hameedath Bivi were commissioned for inter-island service. Unlike other passenger vessels, these catamarans can enter into the lagoon and berth at Kavaratti jetty, eliminating the boat jouney that had to be undertaken to board vessels. This was made possible by deepening the navigational channel in the Kavaratti lagoon. These vessels do not appear to be suited for the islands as they operate only during the fair season and their itineraries are unpredictable due to frequent breakdowns. It is not known whether any study on corals was carried out before and after deepening the channel. It will not be surprising if the area is found to be devoid of live corals.
It epitomizes the degradation of corals due to technological advances in mode of transportation.
Except for Minicoy, Andrott and Kadmat, the total fish landings at other islands have more than doubled during the last few years (Fig. 6). It indicates the increasing number of fishing boats operating from these islands and the proportional amount of live bait resources collected from reefs/lagoons These data do not reflect the fishery resources of the respective islands as fishermen fish in the vicinity of other islands, such as Bitra, Pitti, Suheli, Cheriyakara and Suheli Valiyakara, which harbour rich fishery resources.
Fig. 4. Percentage increase in passenger traffic in Lakshadweep islands. - Agatti
Fig. 4. Percentage increase in passenger traffic in Lakshadweep islands. - Amini
Fig. 4. Percentage increase in passenger traffic in Lakshadweep islands. - Andrott
Fig. 4. Percentage increase in passenger traffic in Lakshadweep islands. - Bitra
Fig. 4. Percentage increase in passenger traffic in Lakshadweep islands. - Chetlat
Fig. 4. Percentage increase in passenger traffic in Lakshadweep islands. - Kadmat
Fig. 4. Percentage increase in passenger traffic in Lakshadweep islands. - Kalpeni
Fig. 4. Percentage increase in passenger traffic in Lakshadweep islands. - Kavaratti
Fig. 4. Percentage increase in passenger traffic in Lakshadweep islands. - Kiltan
Fig. 4. Percentage increase in passenger traffic in Lakshadweep islands. - Minicoy
Fig. 5. Percentage increase in cargo traffic in Lakshadweep islands. - Agatti
Fig. 5. Percentage increase in cargo traffic in Lakshadweep islands. - Amini
Fig. 5. Percentage increase in cargo traffic in Lakshadweep islands. - Andrott
Fig. 5. Percentage increase in cargo traffic in Lakshadweep islands. - Bitra
Fig. 5. Percentage increase in cargo traffic in Lakshadweep islands. - Chetlat
Fig. 5. Percentage increase in cargo traffic in Lakshadweep islands. - Kadmat
Fig. 5. Percentage increase in cargo traffic in Lakshadweep islands. - Kalpeni
Fig. 5. Percentage increase in cargo traffic in Lakshadweep islands. - Kavaratti
Fig. 5. Percentage increase in cargo traffic in Lakshadweep islands. - Kiltan
Fig. 5. Percentage increase in cargo traffic in Lakshadweep islands. - Minicoy
Fig. 6. Percentage increase in fish landings in Lakshadweep islands. - Agatti
Fig. 6. Percentage increase in fish landings in Lakshadweep islands. - Amini
Fig. 6. Percentage increase in fish landings in Lakshadweep islands. - Andrott
Fig. 6. Percentage increase in fish landings in Lakshadweep islands. - Bitra
Fig. 6. Percentage increase in fish landings in Lakshadweep islands. - Chetlat
Fig. 6. Percentage increase in fish landings in Lakshadweep islands. - Kadmat
Fig. 6. Percentage increase in fish landings in Lakshadweep islands. - Kalpeni
Fig. 6. Percentage increase in fish landings in Lakshadweep islands. - Kavaratti
Fig. 6. Percentage increase in fish landings in Lakshadweep islands. - Kiltan
Fig. 6. Percentage increase in fish landings in Lakshadweep islands. - Minicoy
Fig. 7. Fishery statistics of Lakshadweep.
Fig. 7. Fishery statistics of Lakshadweep. - Value of total fish catch
Fig. 7. Fishery statistics of Lakshadweep. - Relationship between fishing catch and effort
Fig. 7. Fishery statistics of Lakshadweep. - Catch/effort vs effort
Fig. 8. Total human impact on Lakshadweep coral reefs
It is necessary to analyze further the fishery statistics of these islands. Coral reefs are considered the most productive among marine ecosystems, annually yielding about 9% of the world fisheries (Smith, 1978). As per the latest figures, the annual fisheries yield of Lakshadweep is around 9000 t, of which tunas constitute 7000 t. Though the total fish catch has only tripled since 1980, its value has increased sixteen fold (Fig. 7). In the absence of refrigeration facilities, most of the tuna catch is parboiled, smoked and dried to produce mas. The relationship between fishing catch and effort as well as between catch per unit effort and effort (Fig. 7) suggest that there is no overfishing. Data of fish catch and fishing efforts by boats operating from the mainland have not been taken into consideration. Data on fishing effort have not been standardized but are realistic, as fishing boats in Lakshadweep are more or less of the same size. The potential fish yield is estimated to be 90,000 t (Jones & Banerji, 1973) while the potential tuna yield is 50,000 t (George e/at., 1977). The pole and line fishing method for catching tuna requires live bait collected from coral colonies, resulting in reef damage. The total live bait catch is around 125 t (Pillal el al., 1995). Thus, an increase in fishing activities will increase requirements of live bait, which will in turn adversely affect the reefs. Modern methods, such as purse seining, gill netting and longlining, need to be adopted to increase the tuna yield. There is also scope for increasing the catch of sharks, bill and sail fishes and diversifying fish products. Floating ship factories with bases at mainland ports need to be introduced by a Lakshadweep Fisheries Co-operative to divert the impact of fishing boats away from Lakshadweep islands (Rodrigues, 1996).
The total impact on reefs can be visualized by sumniing up the percentage increases. In this simple model, population density and density of houses have been assigned a relatively higher weightage. The analysis suggests that Bitra, Kavaratti, Agatti, Kadmat and Kiltan are among the worst affected (Fig. 8). The 500 point level could be considered as the carrying capacity of the reefs that was attained in the eighties. The data could be re-analysed when live coral cover data becomes available.
Future scenario
What can be done to save the reefs? fluman developmental activities have been responsible for the degradation of Lakshadweep coral reefs and there is an urgent need to stop the degradation and reverse the trend. Several suggestions and recommendations have been made (James & Pillai, 1989; Pillai, 1996; Rodrigues, 1996). Due to increased revenue from fish catch, improved medical care and other facilities, the life styles of islanders have improved over the years. Technology has been used to raise the standards of living and it must now be utilized to save the reefs. A study on the attitudes and perceptions of islanders towards reefs needs to he undertaken. If the coral reefs were to be destroyed, the fishery, which is the main source of income for islanders, will collapse. We thus need the reefs and tile reefs need our protection. Let us learn from the symbiotic relationship of coral polyps with zooxathellae which holds the secret of the high productivity of coral reef ecosystems.
References
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