57. Mangrove, Bioethics, and the Environment
C. Govindasamy, A. G.
Viji Roy, C. Prabhahar, S. Valarmathi & Jayapaul Azariah
Department of Zoology, University of Madras, Guindy campus, Chennai - 600 025
Bioethics, looks at ethical decisions of life and environment. In simple terms it could be called "love of life" (Macer, 1994). Love compels us to avoid causing harm to plant and animal life. We should learn to do good to the total system of life. While life is dependent upon water, living organisms (plants and animals) are made of up to 90% water. Of this 90% of water, salt water contributes 71%. It is important to maintain clean unpolluted tropical coastal ecosystems. Rational management of tropical coastal ecosystems should be of worldwide interest because mangrove, sea grass beds and coral reefs are among the most productive ecosystems. Mangrove is an open ecosystem which is sustained by the flow of energy and nutrients (e.g. fresh water delivery and tidal flow) from the neighboring marine and land systems and in turn influences these ecosystems. The term tidal forest is used as a synonym of mangrove. In other words, the mangrove is used in a broad term to mean a salt-tolerant forest ecosystem bound to the inter-tidal shallow-water areas, lagoons, river and estuaries of the tropics and subtropics. Shwamborn and Bonecker (1996) attach special importance to the mangrove forests in the tropics since they provide a significant habitat for a wide variety of animals and plants including many commercially important species. They are the nursery for numerous species of fish and crustacean. They provide natural surf protection, supply wood and are presumably an important carbon dioxide reduction system.
World wide, during 1980's
the mangrove forest covered about 24 million hectares and are
found in the coastal zones of sub-tropical and tropical countries
(Twilley et al., 1992). Presumably the current area covered
by mangroves is between 14 and 15 mill. ha., (Hamilton et al.,
1989). In India, the mangroves forest covers about 360,000 ha.
In Tamil Nadu it extends along the coast for about 1,000 km.
In addition to the scientific study on the mangrove ecosystems,
today, a total of some 8,000 studies on mangroves exist, of which
approximately 2000 have appeared since 1978 (ASFA, 1993). At
present 150-200 studies on mangrove ecology are published in international
journals annually. Yet since at present, large areas of forest
have been forfeited for the sack of human settlement direct utilization
of natural resource establishment of shrimp ponds (for example
in Philippine about 96,000 ha. of coastal lands have been converted
into brackish water ponds for shrimp and fish culture (Tan, 1978))
for agriculture and for firewood purposes. Other indirect stresses
arising from human activities outside the ecosystems, also influence
the total mangrove ecosystem. The paper highlights the distribution
and diversity destruction, utilization, conservation, development
and future options for the mismanagement of this unique ecosystem.
Distribution and Diversity
On the global level, distribution of mangrove forest has coincided with the 20C degree centigrade summer isothermal line (Duke, 1992). The procedure for estimating the area covered with mangroves is also subject to some fundamental methodological problems. Based on the individual researchers who have defined the methodology the extent of mangroves very differently (Kjerfre and Lacerda, 1993). The total world wide area of mangrove forests cited differs from author to author considerably. Reliable estimates range from 17 mill. ha. (Hamilton et al., 1989) and to as much as 24 mill. ha (Twilley et al., 1992). Schnamborn and Paul (1996) have made up to-date estimates between 14 and 15 mill. ha. (Table 1).
Furthermore, the largest
mangrove area occurs in Indonesia, (30%) Brazil (10%) Australia
(8%) and in India only (3%) (Table 1). The mangrove ranges differ
globally quite clearly regarding numbers and diversity of species.
Indian ocean and the pacific region have a large diversity of
species whereas low diversity of species distinguish the America
and West Africa regions (Jordan, 1991). According to the species
lists published by Rao
Table 1: Estimated mangrove
coverage of the 15 countries with the largest mangrove areas.(after
Schwamborn and Paul, 1996).
|Country||Mangroves (1000 ha.)||Global (%)|
Table 2: Number of mangrove
species in the different countries of the earth. (Schwamborn
and Paul, 1996).
Northwest coast of Africa
Southwest coast of Africa
East coast of Africa
Trop. West coast
Trop. East coast
(1987), there are 193 plant
species, 397 fish species, 259 crab species, 256 mollusc species
and 450 insects, mammals and other plants and animals species
diversity world wide (Aksornkoae, 1987). Venkatesan (1966) reported
that the occurrence of 26 species in Godavari mangrove at Kakinada.
Later, Azariah et al. (1992) mentioned that the only 13
species of mangrove plants were present around the Godavari mangrove
areas. Moreover, 13 species were extinct during the last 25 years.
Accordingly, in tidal forests 20 families covering 14 orders with
69 species are to be found. Most of the species belong to the
families of the Combretaceae followed by Rhizophoraceae and Avicenniacea.
Of these three families a total of exclusive 69 species of mangrove
plants (Duke, 1992) belonging to 27 genera (Saenger et al.,
1983) were recorded throughout the world (Table 2).
World wide distribution: 69
Species like, Conocarpus, Lagunculasia, Lumnitzera, Pemphis, Osborinia, and Sonnerabia, Rahizophora, Bruguiera, Ceriops, Kandelia and Avicennia belong to the order Myrtales, Rhizophorales and Lamiales respectively. Furthermore, most of the mangrove plants are viviparous, i.e. seeds mature on the tree until they reach the embryo stage, then fall down and drift away with the currents (Rabinowitz, 1978). Mangrove regeneration has been also recorded in some forms (genus Aarostichum, 3 species world wide) and palms (only species: Nypa fruticans).
In India, there are no uniformity on the survey made on the status of mangrove vegetation. And hence, total area of the Indian mangroves is estimated to vary. Sidhu (1963) reported about 6,819 km2 mangroves in India while, Krishnamoorthy and Jayaseelan (1984) reported that the distribution covers about 6,670 sq. km2. In Indian mangroves more than 64% of the total are found in Sundarbans area and another 18.42% are found in Andaman and Nicobar Islands (UNESCO, 1984). In Tamil Nadu, the total area of the mangroves is about 150 km2 including Cauvery delta and other adjacent coastal stretches (Government of India, 1994).
Furthermore, in Indian mangrove
forest, flora is comprised of more than 60 species belonging to
41 genera, 29 families and 26 species, in the East coast. Eight
species, that are present in the West coast, are absent in the
East coast (Untawale, 1984). Of these 60 species, 30 and 18 species
are found in Sundarbans and Tamil Nadu respectively. Neskar (1990)
reported that at present only 30 true mangrove species and 30
holophytic mangrove associated flora are available in tidal and
inter-tidal mangrove forest of Sundarbans. Very recently, Banerjee
(1997) made extensive surveys throughout the coastal regions and
reported that the distribution and zonation of the mangrove species
is related to the variation of topographic features and major
ecological processes. A total of 65 mangrove species is recorded
throughout India. Of these, 62 are found in the Sundarbans, 63
in Mahanadi delta, 29 towards the Godavari- Krishna- Cauvery and
west coast region and 30 in the Andaman and Nicobar Island. Distribution
of mangrove species indicates that floristic diversity and richness
of species gradually taper from Sundarbans - Mahanadi delta southward
and become much less along the west coast from down south in Kerala
to Saurashtra and Kutch regions in the north.
Destruction Of Mangroves
With the global destruction
of tropical forests increasing attention has recently been drawn
to the ecosystem of the mangroves forests, which are being threatened
to an even greater extent or have already been completely destroyed.
In the past, mangrove areas were generally regarded as useless
and hostile territory. They were not considered to be valuable
and were therefore destroyed in varying ways. About 80% of previously
existing mangrove forests have been devastated or have been subjected
to degradation as a result of land deposits, construction of sanatory
landfills or simply due to overuse, whether this be through charcoal
extraction or the setting up of aquaculture (Bittner, 1996).
A. Natural destruction
Both the vegetation and
the habitat have to cope with many natural destruction, such as
devastating tropical storms and tsunami caused by seaquakes. Such
events are common in the Caribbean and the Bay of Bengal and forests
may take decades to recover. Latest severe cyclone damage has
caused extensive damage in Southwest Bangladesh in the year 1988,
concurrent with a storm surge of 5 m, which destroyed some 8.5
million trees of the two predominate mangrove species which equivalent
to 66.30 million m3 of commercial saw timber (Kapetsky,
1987). Further, the large scale environmental changes following
microclimate variations; abnormal sea level fluctuations, salt
accumulation in soil or flooding have also contributed for the
destruction of mangrove forests. During the past three decades,
the most important mangrove tree species of the Sundarbans, contributing
some 60% of the area's marketable saw timber has been affected
by a disease described as "top dying". Biological
pests can also have severe impacts on both individual plants as
well as on the whole forest ecosystem. Epidemics of bacteria,
fungi, spiders, leaf mining, herbivorous or wood-destroying insects
and many invertebrates such as mussels, barnacles, leaf eating
crabs, small fishes, shrimps and wild mammals can alter entire
forest landscape (Mastaller, 1996).
B. Man made destruction
Without doubt most of the
recent mangrove destruction around the world has been due to man.
Decline of mangrove resources has reached alarmingly high rates
all over the world (Table 3).
Table 3: Example of the
(estimated) world-wide decline of mangrove forests in recent times
|Country/ Region||Period of record||Estimated original mangrove area(ha)||Estimated present mangrove area(ha)||%|
U. S. A
South India (Kerala)
a. Land reclamation for settlement
Tidal forest have always been closely related to the historical development of tropical countries. The Indian subcontinent renders an impassive example of how mangrove areas have always suffered from conversion due to colonization, migration and population explosion. When Bombay was founded in 1670, the entire mangrove vegetation was clear felled to make way for a thriving trade metropolis. In history, the continuous land reclamation was taking place, since the beginning of British Colonial times in 1770. In Tamil Nadu, the palynological studies carried out by Tissot (1987) indicate that the species of Rhizophora and Sornneratio have disappeared completely now. Azariah et al. (1988) have debated the negative impacts of urbanization on the status of mangrove swamps of Madras. The uncontrolled and unregulated exploitation carried out by the authorities of the Chatram and Revenue Department, as well as due to some unscientific policies introduced in 1920 and thereafter coupled with poor attention paid towards the replantation of the mangrove plants, are some of the causes responsible for the present poor species diversity of the Muthupet mangrove forest (Azariah et al., 1992).
For example, in the largest
delta region of the world extending between India and Bangladesh,
some 150,000 ha. of mangrove forest disappeared during the past
100 years, when areas were reclaimed for agriculture settlement
sites, industrial set up, industrial estates and road networks
for an ever-increasing coastal population. As in most places in
the Indian subcontinent, coastal roads and industrial estates
were placed in reclaimed mangrove areas to minimize conflict with
existing agricultural interests. (Mastaller, 1996). Further, the
southern part of India, like Kerala, were the rate of population
increase is the highest in the country, some 70,000 ha. of mangroves
were cleared at the turn of century. At that time, Kerala had
about 1.5 million inhabitants. Today, some 22 million people crowd
the coastal belt of 600 km by 25 km, resulting in 1500 people
per square kilometer. It is no surprise that only 3.5% of the
former mangrove vegetation survives. After effects of such extensive
mangrove clearance is the closure of the lagoon system and the
water quality has become very poor, converting many parts of the
lagoon into stagnant acidic pools. Nowadays, the standing group
of phytoplankton, shrimp production has been reduced significantly.
(Mastaller, 1996). The conclusion drawn is that only a broad and
intact natural mangrove belt could effectively act as a buffer
against these recurring man made forces and give reasonable control
against reclamation of coastal lands.
b. Conversion into fish and shrimp farms
During the past three decades about 196,000 ha, and 42,000 ha, of the Philippine and Ecuadorian coastal lands have been converted into brackish water ponds for fish and shrimp culture respectively. That is about 70.4% of the initial stand or about 143 km2 a year or 39 ha. per day. Between 1968 and 1983, some 237,000 ha. of mangrove forest have been lost to this industry almost half of the total national mangrove area (Fernandez, 1978). In fact, the operation of brackish water pond in mangrove wet lands is anything but a failure both in economic and ecological terms (Govindasamy and Kannan, 1996). In 1962, when about 235,000 ha. of mangrove were still recorded in Ecuador coincided with an aquaculture bloom. Hence, since the early 1970 to 1983, Ecuadorian mangrove forests have been under increasing pressure. When shrimp exports were in peak condition, about 42,000 ha of mangrove forest were converted into brackish water ponds (Terchunian and Klemas, 1986). Further, in 1960 to 1980 and 1980 to 1986 shrimp farming in Thailand had a 32.2% and 64.2% share in the definitive conversion of mangrove forest area respectively (Uthoff, 1993). Accordingly, more than 96% of the mangrove land were converted to shrimp farming during the past 33 years.
In India, the fast growing industrial development has taken much of the coastal areas. For example, in 1990, Indian government has permitted fertilizer complexes namely Godavari Fertilizer and Chemical Ltd. (Capital cost of Rupees 1080 million) and the Nagarjuna Fertilizer and Chemical Ltd. (Capital cost of Rupees 6,700 million) along the Kakinada coast. These two fertilizer factories have affected the ecosystem to an extent of 200 km range from these factories. In view of such as rapid place of industrialization in the coastal zone of Kakinada (Azariah et al., 1992). There is a need for striking a balance between industrialization and conversion.
Very recently, Govt. of India (1994) reported that about 330 km2 mangrove patches have been converted into Housing units in Ratnagiri, Vijayadurg, Malvan, Devgad, Elephant cape Island, Mihim creeks and Vikahroali. According to The Hindu News (1995) more than 20,000 acres had already converted to shrimp farm in and around the Tamil Nadu and Pondicherry state. Of these 20,000 acres more than the 5,000 acres are situated around the mangrove ecosystem of Tamil Nadu. Mangrove forests in India have been converted to other uses to satisfy various human demands since earlier times. The latest survey of the mangroves of India conducted in 1992 (Government of India) revealed that of the remaining mangrove forest amounts to 360,000 ha. Destruction during the period, 1985 to 1994 was incredibly high at 25 ha. per year. The highest rate of mangrove destruction occurred in the southern and eastern parts of India. Forest clearance and land reclamation for aquaculture (especially shrimp ponds), urban settlements and industrial activities have all contributed to the diminishing of mangrove forests in India.
For many years experts from
all over the world have decried this development as economic and
ecological lunacy. Reportedly the major part of the shrimp farms
operate for below their production potential. In spite of the
increasing use of antibiotics, chemicals and increasing inputs
of modern equipment the survival rate in the more than 1,20,000
shrimp culture ponds is only modest (Mastaller, 1996).
Human activity is becoming
the main cause of ecosystem changes in the world. Documented effects
of human activity can be seen everywhere in the world, from atmospheric
to oceans, from the highest mountains to oceans including mangrove
area. The concept of stewardship is required to maintain a sustainable
way of life, and a healthy world. Environmental problems may be
traced back to the beginning of civilization, but are getting
worse with the global scale of air and water pollution including
the introduction of new chemicals and the ever growing human population.
Discharge of polluted water, chlorine pollution from domestic
sewage and industrial pollution may inflict severe damage on mangrove
communities. The extensive brackish water lagoon off Lagos, the
Nigerian capital, serves as an example: every year some 25 to
30 million litres of untreated fecal matter are pumped into the
lagoon. The annual volume of domestic garbage, industrial discharge
and chemical pollutants is not yet determined, but estimates assume
similar magnitudes. Insecticides and herbicides from adjacent
agricultural and mangrove plants and animals also contribute to
the general degradation and contamination of the mangrove and
other vegetation around the lagoon and mangrove area, and continually
reduce the number of species living there (Mastaller, 1996). The
bioethical issue is that we should try to avoid harm, and attempt
to understand the consequences of direct and indirect effects
of our actions on a complex mangrove ecosystem.
Human Relationships With Mangrove
In conclusion we have a deep and eternal relationship with mangrove and water. The first relationship we have is dependence. The estimated annual global use is the yield of fish, shrimp and other medical uses from mangrove plants and animals (GESAMP, 1990). By the year 2000 about 70% the 2% of the population will be living around the mangrove area. The dependence is both indirect and direct. Beside the obvious ethical issue of just distribution of resources, which affects human relationships in the biosphere, there are further relationships between people and mangrove environment.
Mangrove has deep meanings
for the people, and by exploring this relationship we may not
only understand more the relationship between living organisms,
people and the mangrove environment, for fishing aquaculture,
and enjoyment but also we may understand more of ourselves. In
the global age, the question of conservation of this heritage
common requires judicial activism to provide very important precedents
and lessons for the further global planning. It also provides
a precedent for protecting mangrove.
Ecological and Economical Importance of Mangrove Destruction
Mangrove forest trend to react sensitively towards disturbances from outside the system. An important habitat for plants and animals is lost and many species may have disappeared from an area, either through extinction or out migration. This may lead to a reduction in the number of species or number of individuals in large water birds and mammals, mass fish mortality and decreasing levels of spawning in fish and prawns. On a global scale, the loss of mangrove wet lands means a loss of critically important wet land for many migratory species. The world conservation union (IUCN, 1993) recognizes many mangrove associated species in their Red list (this list of mangrove associated plants and animals at risk, includes, among others 14 orchids, 11 reptiles, 65 birds and 15 mammals), (Mastaller, 1996) i.e. species which are threatened or vulnerable to extinction. Many of the medicinal plants may be lost when the global destruction of mangrove forests continues in its present scale.
Inevitably most people living
in or associated with mangroves suffer economic losses once this
ecosystem is disturbed or eliminated. The destruction of mangrove
ecosystems, the local fisheries is affected, economically and
socially. Industrial fisheries experience a decline in near shore
fish and shrimp catches which are directly or indirectly linked
to the status and spatial extent of tidal forests.
Conservation, Utilization And Development Of Mangrove Ecosystem
The question now arises
is that how ecologically sound and economically feasible schemes
of utilization, conservation and development can be conceived
under such conditions? What are the possibilities of conserving
tropical mangrove forest except by complete exclusion of any interference?
Considering the essential structural and functional features of
the mangrove forest we can say, with confidence, that the forests
on acrisols and ferrasols suffer logging without degradation provided
good practices of harvesting and possible supporting tissue culture
are applied. However, the basic processes and the physico ecological
significance of structural features of the mangrove forest such
as species diversity, aerodynamic roughness etc. are as yet insufficiently
understood. But this understanding is needed to assess the feasibility
of interference and to optimize management systems. Further, with
the help of effective management which takes various conditions
of this highly delicate ecosystem into consideration, will it
be possible to preserve its genetic multiplicity for future generation.
In order to ensure an adequate level of protection, it is essential
to recognize the value of ecosystem on a global scale. This applies
to a wide spectrum of areas, from nature reserves in the narrowest
sense, whereby the legitimate interests of the indigenous population
must be taken into account to the planning of specific reforestation
measures and suitable systems of utilization. In addition, it
is essential to promote further advancement of basic scientific
research on these ecosystem.
The First author (CG) thanks the Department of Zoology University of Madras and the University authorities for facilities and encouragement and he also thanks the Council of Scientific and Industrial Research, Government of India for the financial support.
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