1. INTRODUCTION
Coral rock is the main aggregate for most construction purposes in Maldives. In 1986 the demand for coral aggregate for the construction industry in Malé Atoll, the industrial center of the country, was estimated at 0.5 million cubic feet/year. Although no recent estimates have been made, it is thought that demand is probably at its limit now and according to predictions, the current methods of mining would exhaust the coral buildings in N. Malé Atoll within a maximum of 30 years if coral mining is not controlled. There are many problems associated with the current mining practices. Biological surveys of mined sites indicate mat the coral diversity and abundance have been decreased dramatically. In addition to this, little recovery was seen at sites intensively mined over 16 years ago.
2. MALDIVES - A BACKGROUND
2.1 Location and Physical Structure
The Republic of Maldives form the central and the largest part of the Chagos-Laccadive Ridge, which extends from west of India into the Indian Ocean and consists of atolls and associated coral structures (Fig. 1.). The archipelago (07° 07'N to 00°42'S and 72°33'E to 73° 44'E), consists of about 1200 low-lying islands forming 21 natural atolls and represents one of the largest coral atoll groups of the world.
Although its territorial area is considerable (90,000km2), a relatively small proportion of the total area (=300km2) is dry land. Of the 1300 or so islands only 202 are inhabited. The total length from north to south is 753 km while the widest point correspond to 118 km.
The physical setting of the Maldivian atolls varies from open structures with numerous islands, faros (ring-shaped reefs) patches and knolls in the atoll lagoon and around the rim to almost closed structures with few lagoons, knolls and patches. Faros are ring-shaped reefs emerging during tidal low water each with their own sandy lagoon and are separated by deep channels. They generally have a rim of living coral consisting of branched and massive types. Patches rise to 40 meters above the lagoon floor and are topped by robust wave-breaking corals. Knolls do not reach the surface and often support profuse coral growth, as do the reefs associated with many of the islands.
In geological time the filling up of the lagoons of faros by reef sediments has resulted in the formation of coral reef islands. The geomorphology of these islands varies tremendously in different atolls and it is influenced by a variety of factors such as location, climate, currents, tides, sea level change and also human factors. The islands are thought to be situated on top of layers of beach rock (about 1m thick), underlying the islands at about 30cm to 60cm above present mean sea level (Preu & Engelbrecht 1991). At the edges of the islands the beach rock dips slightly seawards and forms a platform on which the beach sediments are seasonally transported around the islands. Within the atolls, the water depth is about 60 meters, but just outside some atolls the depth can go up to 3000 meters.
The traditional lifestyle of the people had almost negligible impact on the marine environment, but recent socio-economic developments have led to marked deterioration of the environment. With the increase in population growth and increased wealth from tourism and fishing, the pace of development have increased at a significant rate in the country, during the last two decades.
The need for land led to land reclamation programmes. Harbours are dredged to facilitate economic growth in islands. The demand for building materials in the form of coral nodules has increased steadily and coral mining has become a major environmental concern in the country. In addition to this the country is faced with localised environment impacts as a result of tourism and waste discharges.
2.2 Economy
Being a country with more territorial sea than dry land, the Maldivians depend on resources almost entirely from the sea. The coral reefs which built the country play a vital role in the economic and social well-being of the country.
Fishing and tourism are the two main industries in the Maldives. Both these industries are very promising with potential for growth. They both rely on healthy reefs for their survival and continuity. The majority offish caught are tuna and tuna-related species. Other reef dependent species offish and invertebrates are also exploited.
2.2.1 Tourism
Tourism was introduced to Maldives in 1972 with the opening of Kurumba Village Resort in North Malé Atoll. After two decades there are 73 beach resorts scattered in North and South Malé Atolls and Ari Atoll. Tourism now represents the largest industry in the Maldives.
The physical setting of atolls and associated small coral islands allow uninhabited islands to be chosen for resort development in the Maldives. Hence one island is one self-contained resort with its own facilities.
In the 70's and 80's significant quantities of coral were used in the construction of resort islands. Current tourism regulations discourage the use of corals for building purposes at resorts. Even so maritime structures such as breakwaters, jetties and groines are still constructed using corals.
The coral reefs around the resort islands (house reefs) and reefs in their proximity represent the basis of tourist activities and hence are very important economically for resorts. Fishing and mining from resort house reefs are discouraged by all resorts.
2.2.2 Fisheries
Tuna fishing is the second largest industry in the Maldives. With the mechanization of fishing vessels in the early 70's, and the establishment of freezing facilities the fishing industry has developed at an enormous rate. Catches of tuna and tuna like species have tripled from 30,000 MT in 1970 to 100,000 MT in 1994. The principal fishing atolls are: Haa Alifu, Raa and Baa, Faadhippolhu, Kaafu (Malé), Thaa, Laamu and Gaafu, representing 75% of the total fish landings.
The main composition of fish catch is skipjack tuna (Katsuwonus pelamis), representing 50-75% of the total catch. The second most important species caught is the yellowfin tuna (Thunus albacaraes). The main fish products exported are: frozen skipjack tuna, canned fish, dried fish and salted dry fish.
The tuna fishery is based on pole and line fishing and significant amounts of baitfish are used during the process. Baitfish for the tuna fishery are collected from coral reefs. The bait used are relatively small (4-8 cm length) and about a dozen species are caught along reef edges. Bait fish are essential for the tuna fishery and reduction of bait catches will have adverse effects on the tuna fishery.
It is believed that coral mining disturbs the baitfish populations and currently coral mining is banned from common bait fishing reefs.
3. CORAL MINING IN MALDIVES - BACKGROUND
3.1 Introduction
Coral mining is an important activity in Maldives having long-lasting impacts on reefs. Coral is virtually the only building material available in the country and coral mining is widespread. The demand for coral has increased at an enormous rate during the last decade owing to increased development in the country. Recent studies had led to concerns over the sustainability of the reefs subject to coral mining activities.
Coral reefs in Maldives represent strategic natural offshore sea-defense. They are also important as habitat for baitfish and a primary source of building material. Coral blocks have been historically used for buildings and road construction. The coral blocks are extracted from shallow reef flats at 1-2 meters depth, with the help of iron bars to break up the living coral.
3.2 History of Mining
Corals had been mined in Maldives for decades. Coral mining is a labour intensive activity and hence it is relatively expensive to obtain compared to other forms of building materials. Furthermore imported cement or lime (produced by burning coral rock and coral rubble) is required to hold coral pieces together in the construction of coral walls and structures. Both cement and lime are expensive to buy. Historically the local communities used coconut leaves and variously locally available timbers to build houses. Corals were only used then for more important constructions such as in tomb stones and for mosques. In most cases large Porites heads were collected for such works. The old mosques and monuments in the country built a hundred years back indicate how extensively massive corals especially Porites may have been mined.
With the mechanization of the fishing industry in the early seventies with more money being generated within the island communities, construction of coral houses became the first priority for any land owner. It was simply a luxury to have a house built of corals and coral aggregates in contrast to a house of predominantly coconut products.
To own a coral built house was also considered prestigious and a reflection of good living. As a result coral mining expanded year to year.
With the introduction of tourism in the country in the early seventies and with the increased development in Malé, the construction industry grew at a tremendous rate with demand increasing exponentially. The prediction of demand for coral is that the limit will be reached in 2015 A.D. Suitable reefs had become scarce and the government had imposed tentative regulations for coral mining activities in the country.
3.3. Uses of Corals
Corals are mined in Maldives mainly for the construction of houses and buildings. The common species of corals mined are massive corals such as Porites. Massive corals are crushed by manual labour into irregular and smaller pieces and used to build walls. Lime, cement or concrete are used to bond the coral pieces together to form walls and other building structures.
Another major use of corals is in the making of lime. For many islanders it is cheaper to produce lime locally than buying imported cement. Coral and coral debris collected from the reefs are burned in a pit in the ground with locally available firewood. Coral rock are converted to lime by this high heat treatment and are used to bond coral pieces to build houses and other constructions.
To a minor extent, corals are used as ornaments and jewellery (black corals) and for decorative purposes.
Groins, solid jetties breakwaters and sea walls which are common features in many resort islands as well as in some local islands are constructed from corals. The huge amounts of coral used for these artificial maritime structures should not be underestimated.
3.4. Coral Mining Areas
Until quite recently, corals were usually mined from the reef flats of islands house reefs. In many islands the reef is reasonably close to the island and it is simply a matter of collecting and loading a small boat to carry the corals to the island. Current regulations do not allow coral mining from island house reefs. People who mine corals as an income-generating activity choose accessible shallow ring reefs locally known as faros, to mine corals. Mining is carried out at the rims towards the inside of the reefs. In atolls with few ring reefs it is more common to find mining activity at lagoon side of outer atoll rim reefs.
3.5. Methods of Coral Mining
Coral mining methods and techniques are manual and labour intensive. Having chosen a suitable reef the miners travel to the site on a small dhony (a wooden boat). Mining starts from the inner edge of ring reefs. Corals are dug and broken up with iron bars to manageable sizes. Some massive corals may be small enough to be mined without breaking. The corals are lifted by hand on to the boat. When the boat is full it is carried to the island, where the coral lumps are left for a period of time to dry and clean by sun and rain.
3.6. Trends in Demand for Corals
With the increased pace of development in the country especially in Malé Atoll, the demand for coral rock for construction works is at its limit. Demand has increased tremendously during the last decade. Figure 2 shows the quantities of corals mined in Malé atoll in the period 1980-1985. The extraction figures for coral mining given by Brown & Dunne (1986) showed that corals were been mined at the rate of 0.5 million cubic feet per year, where the industrial needs were the most responsible by the numbers of coral rock extraction. This figure is based on only Malé Atoll and is likely to be much higher now.
Figure 2. Quantities of coral mined in Malé Atoll in the period 1980-1985
Reproduced from: Brown, B.E. & Dunne, R.P. (1986)
3.7. Mining as a Commercial Activity
Coral mining is not a country-wide commercial activity except for one or two atolls in the country. Mining is carried out at a minor scale in many of the atolls. Large scale commercial mining is only carried out at one atoll adjacent to Malé Atoll. In this atoll (Ari Atoll), in two islands in particular (Fenfushi and Maamingilli), coral mining represents a major income generating activity. They work under contracts for the Malé construction industry, tourist resort islands and also for many other atolls countrywide. Recent harbour improvement projects in many atolls of the country had led to an increase in the demand of corals for harbour wall constructions. Fenfushi and Maamingilli island miners work under contracts for these islands too.
In the early eighties, the cost of coral rock varied between 0.33 and 1.10 Rf per cubic feet. A typical size "dhony" (local wooden boat) load is approximately 200 ft3 and therefore would cost between 66 and 220 Rf (l US$ =11.72Rf). A group of miners working 8 hours a day can mine one dhony load of corals. They can therefore earn up to 6000 Rf for a month for a single dhony. In most cases this figure can be much higher because depending on the site proximity to the target area more than one dhony load can be collected for a day, which is more normal. The current prices of corals are much higher and vary between 500 and 600 Rf per 200 cubic feet.
Clearly coral mining is an important source of income at least for a few atolls. The government is aware of the financial loss of income to these miners when it seeks alternatives for coral mining. But it is concerned about the scale of mining activities at present.
3.8. Existing regulations regarding coral mining
The government is worried about the environmental implications of coral mining. Prior to 1992 there were very few regulations as to where people could or could not mine corals. It was then simply a matter of protecting properties such as islands belonging to individual owners. In 1992 preliminary regulations were introduced to combat uncontrolled mining activities. The following controls are now in effect in the country.
1. Mining cannot to be carried out on island house reefs.2. Mining cannot be carried out on atoll rim reefs and common bait fishing reefs.
3. Applications are required to be submitted to the atoll offices through island offices by any one needing corals to build any structures and permissions need to be granted by the atoll office before any mining can be carried out.
4. The island office is required to estimate the quantity of corals required for the applied construction work and hence should ensure that only the required amount is granted.
5. Every island is required to keep a log book of the amount of corals mined.
The Ministry of Fisheries and Agriculture is the responsible government authority for the formulation of regulations regarding coral mining. The ministry has been working for sometime to formulate a comprehensive coral mining regulation and more stringent controls are expected sometime in 1996.
Under the new regulations coral mining will be restricted to specific areas marked on maps and mining activities will be monitored very closely.
4. ENVIRONMENTAL IMPACTS OF CURRENT CORAL MINING ACTIVITIES
Coral mining represents the most important threat to the reefs in the Maldives. Population growth, and increased wealth from tourism and the fishing industries, has created a steadily increasing demand for building materials in the form of coral nodules and stand.
The biological and physical impacts of coral mining on reefs in Malé Atoll, Maldives were investigated by Brown and Dunne (1986; 1988). They reported that live coral cover on reefs subject to coral mining was very low compared to unmined reefs. Response to reef associated fish to coral mining was reported by Shepherd et al. (1992) and Brown et al. (1990). Fish community structure was compared on mined and non-mined reef flats and their adjacent slopes. Abundance of reef fish was found to be low on mined reefs compared to non-mined reefs.
Biological surveys of mined sites indicate that coral diversity and abundance decreased dramatically. In addition to this, little recovery was seen at sites intensively mined over 16 years ago. Of particular concern is not only the apparent failure of mined reef flats to recover but the consequent loss of both coral and associated reef fish resources to the economy (Brown et al. 1990).
Coral mining is highly destructive and is carried out at a high cost to the reef environment with a very small return of corals as building material. It was estimated that 1 ha of reef flat corresponds to 3000m3 of coral rock (Brown et al. 1990). Assuming that approximately 10m3 of coral aggregate are required to build an average local house (20-30m3 or two to three storey buildings), 80m3 to construct 8 groynes of 10x1x1 m each, at a tourist resort island, it is not difficult to estimate how much it takes to exhaust 1 ha of reef flat. Coral jetties, groynes and seawalls are common structures in many resort islands as well as in local islands.
4.1 Biological Impacts
Coral mining represents a questionable activity for the maintenance of the reef equilibrium. Brown and Dunne (1988) indicated clearly the high disturbances to coral reefs in the Maldives as a result of coral mining. Even though the targeted species were usually massive corals, the process of mining disturbs many other coral species in the area primarily as a result of trampling and sedimentation. Mined areas of the reef were simply wiped out. However, it must be noted that the effects are very localised on the reef itself. Mining is carried out only at the reef flats and hence there is little effect at the slopes of such reefs.
4.1.1. Corals and reef-fishes
Live coral cover was greatly reduced at mined sites as observed by Brown and Dunne (1986). Table 1 shows the history of 8 sites investigated by Brown and Dunne (1988) in North Malé Atoll and Fig. 3 shows the live and dead coral cover at these sites.
Live coral cover was obviously very low at mined sites. Rehabilitation and recovery of reefs subject to mining activity was found to be extremely low.
The main reason for this was the chronic substrata disturbances which resulted from the mining procedures. It seems that as a consequence of the rubble mobility from the mining activities, the mechanical abrasion and higher water-movement limit the coral larvae settlement. Loose rubble prevents any successful settlements for quite a long time. Sites which have been mined since 16 years ago, presented very low coral cover (approximately 0.5% total cover). However a site which has been mined for only 5 years already shows a very low coral cover (1%), as well.
Table 1. Summary of the Histories of Sites Examined in North Malé Atoll.
|
Site No. |
Description |
History |
|
1 |
Submerged reef N. Malé Atoll |
Used for coral mining at least 16 years earlier |
|
2 |
Submerged reef N. Malé Atoll, S. Kuda Bandos |
Used for coral mining at least 10 years earlier |
|
3 |
Submerged reef N. Malé Atoll, N. Villingili |
Used for coral mining in recent years |
|
4 |
Submerged reef N. Malé Atoll |
Control: not used for coral mining |
|
5 |
Submerged reef N. Malé Atoll |
Control: not used for coral mining |
|
6 |
Submerged reef N. Malé Atoll |
Control: not used for coral mining |
|
7 |
Submerged reef N. Malé Atoll |
Control: not used for coral mining |
|
8 |
Submerged reef S. Malé Atoll |
Control: not used for coral mining |
From: Brown and Dunne, 1988
Figure 3. Percentages of live and dead coral cover recorded at mined and non mined sites
From: Brown and Dunne, 1986
Diversity of corals, live coral cover and resident reef fish abundance are very low at mined sites, where the main coral species collected constitute in Porites lutea, Goniastrea retiformis and Platygyra lamellina (Brown & Dunne (1986). Figure 4 shows the fish counts and coral genera encountered at sites mined to various levels with sites not mined at all as observed by Brown and Dunne (1986).
Figure 4. Numbers of coral genera and reef fish families encountered at mined and non-mined sites
The presence of reef fishes follows the same pattern as for coral reefs. Low fish diversity characterizes the mining sites, where the dominating species are herbivorous pomacentrids and acanthurids.
Although the number of species of reef fish are greatly reduced at mine sites this does not have much of an effect on the reef fisheries as a whole. Commonly exploited reef fish inhabits the reef slopes which are normally out of reach of the coral miners.
It is known that the growth rate of massive corals such as Porites is extremely low. Hence the removal of such corals will have long term consequences on the diversity of reefs with a long recovery time. There may be many factors affecting the growth of corals on mined areas as a result of alterations in conditions such as light, sedimentation, wave energy, nutrients and degree of exposure.
Brown et al (1990) reported that mined reef flats had a significantly lower presence offish. A visual census of mined and non-mined reef flats showed 60% reduction of fish species at mined sites. There was a positive correlation between rugosity index and diversity and biomass offish. Coral mining on reef flats resulted in low rugosity (structural complexity) and, consequently, lower diversity and biomass of fish.
The effects were more evident for corallivores (Oxymonacanthus longirostris, Chaetodon trifasciatus, Chaetodon triangulum), and benthic herbivores and aquarium fish (Acanthurus leucosternon; Oxymonacanthus longirostris, Pygoplites diacanthus).
The reduction of corallivorous species is explained by the destruction of corals, which are their primary food sources and a retreat for them as well. Benthic herbivores use the reef structure in order to find shelter from predators. Common species of aquarium fish declined because of the loss of habitat. The abundance of bait fish Chromis atripectoralis was also reduced at the mined sites, possibly as a result of loss of shelter in the area and reduced abundance of zooplankton. It is thought that bait stocks, principally the baitfish Chromis atripectoralis, may be affected by habitat disturbance. The schools of bait fish live close to coral reefs, where they find food and protection against predators.
If live bait supply is reduced by habitat disturbances due to coral mining, the tuna fishery may be severely affected. The supply of bait fish is essential for the pole and line tuna fishery, which in turn is important for the economic and social well being of Maldives.
4.2 Physical Impacts
Physical impact of coral mining depends on the type of reefs in question. No immediate effect may be observed with coral mining at an isolated ring reef. However if house reefs of islands are subject to mining activities there may be adverse effects. Island house reefs act as physical barriers, protecting the coral islands against wave action, by dissipating most of the energy in the incoming waves before they reach the beach line. Mining corals from the reef flats effectively remove this physical barrier and leave the islands prone to increased wave action, swells and storm surges and consequently beach erosion. The sediment dynamics of coral islands may be altered too as a result of altered flow regimes.
5. ALTERNATIVES FOR CORAL MINING
5.1 Use of concrete blocks
Concrete blocks form a more environmentally sound and cheaper alternative to coral mining. Sand needs to be mined for the construction of concrete blocks. It is thought that sand mining may be less destructive than coral mining. Sand mining, however, should be carried out at sand banks or from shallows of isolated reef systems rather than from island beach systems.
Concrete blocks are made from a mixture of sand and concrete. The mixture is put into mould to obtain the required shapes and sizes. An indicative mixture for foundation is 3 parts of sand for 1 of cement, while for wall, the mixture is 5:1. The coral sand have to be very well washed whit fresh water, in order to extract the salt. The cost of hollow concrete represents 80% of the cost for coral nodules.
It is believed locally that hollow concrete blocks are not strong enough to construct buildings. As a result many people prefer coral rock to concrete blocks in construction work. However, experts believe that if the right mixing levels are employed for sand and cement together with the right size of coral sand, concrete blocks could prove to be as strong as corals and would constitute a viable alternative to mine coral rock.
There are small-scale concrete blocks manufacturers in Malé and other Atolls. It is also common to find more and more people resorting to use of these blocks simply because obtaining coral rock is becoming more and more scarce and prices are high.
5.2 Use of imported aggregates
Imported aggregates are preferred 10 locally available materials in the construction of large buildings in Malé.
Consideration may be given to the tax levied on imported aggregate so that more people could effort to buy such materials.
5.3 Mining an entire reef
An alternative proposed for the current methods of coral mining is the use of a special dredger, to quarry an entire single reef. The implications are that this would improve supply, as well as stop the current destructive mining activities at least in Malé Atoll. Such an activity was already carried out some years ago by the Royal Air Force at the Atoll in South Maldives.
Brown and Dune (1986) looked into the impacts of coral mining on the reefs of Maldives and one of their recommendations as an alternative to coral mining was to consider selecting a single faro knoll or patch within and atoll and dredging such a faro up to the lagoon floor. The indications were that an average size reef of 2000 ft diameter would yield enough aggregate for the construction industry for more than a hundred years.
Blasting and dredging a single faro (submerged reef) with an average size of 30 ha and 15m depth, can produce 1.5x103 of coral rock. If the same area is exploited from the lagoon floor the material resultant is about 10 million m3. These values represent a tremendous increase of material compared with the traditional method, which represents only 5000-7500m3.
The advantage of mining an entire faro is the higher efficiency and supply of material for more than a century, according to the needs projection of the development planning of Maldives. The suggestion was that it is better to loose one faro (reef) than all economically important reef flats in any given Atoll.
6. CONCLUSIONS
Coral reefs are economically important to Maldives in terms of revenue and ecosystem services, particularly as a buffer to shorelines from wave action and other oceanic processes.
Coral mining is a questionable activity with respect to maintaining the reefs in equilibrium.
The successful management of coral mining activities is based upon a strong legal foundation, which defines the environmental standards related to coral mining.
The government of Maldives is concerned with the environmental implications of coral mining and is determined to control mining with legislation.
An alternative source of building material needs to be identified in order that coral mining be completely banned.
REFERENCES
Brown, B.E. and Dunne, R.P. 1988. The environmental impact of coral mining on coral reefs in the Maldives. Environmental Conservation, 15,2:159-166.
Brown, B.E. and Dunne, R.P. 1986. Report on a Preliminary Investigation into the Environmental Impact of Coral Mining on the reefs in the Maldives.
Brown, B.E.; Shepherd, A.D.S.; Weir, I. and Edwards, A.J. (1990). Effects of degradation of the environment on local reef fisheries in the Maldives. Final report to the Overseas Development Administration.
Kenchington, R. 1985. Maldives Report on Behalf of UNESCO. Report on Missions to the Republic of Maldives, October 1984-February 1985.
Naseer, A. 1993. Coral reef management in the Maldives with special reference to reef monitoring: the use of line transect method for reef monitoring in the Maldives. Msc Thesis, Newcastle University, 1993.
Preu, C. and Engelbrecht, A. (1991). Patterns and processes shaping the present morphodynamics of coral reef islands - Case study from the North-Malé Atoll, Maldives (Indian Ocean).
Preu, C and Engelbrecht, A. (1991). Patterns and processes shaping present morphodynamics of coral reef islands - Case study from the North Malé Atoll, Maldives (Indian Ocean).
Shepherd, A.R.D.; Warwick, R.M.; Clarke, K.R.; and Brown, B.E. (1992). An analysis of community responses to coral mining in the Maldives. Environmental Biology of Fishes, 33:367-380.
