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eastern Africa. Mangrove’s three genera, namely, Acrostichum, Avicennia and
Rhizophora have the global presence (Spalding et al. 2010). More than 50 mangrove
species grow along the coast of Asia and that is the highest among all the continents.
Oceania region also supports more than 50 species of mangroves. Australia has
about 30 species. Africa has about 14 species of mangroves. South America as well
as North and Central America have only ten mangrove species (FAO 2007).
19.1.2 Threats to Mangroves
Despite the ecological and economic significance of mangroves they are considerably under pressure from human activities. Its area has declined by 30–50% in the
past 50 years, a higher rate than most other biomes (Balmford et al. 2002). It has
been estimated that the loss of world’s mangrove forest may be as high as 60% by
2030 (UNEP-WCMC 2006; Alonge 2002; Valiela et al. 2001). The major threats to
mangroves are:
Plantations and young plants are being damaged by the attachment of barnacles
to their stem. Insect attack also causes considerable damage to the leaves of various
species of mangroves like Rhizophora mucronata, Avicennia alba and Sonneratia
alba. Other species have also been found to be attacked by fungus.
Reduction in the quantity and periodicity of fresh water flowing into mangrove
wetlands affects the density as well as diversity of the mangroves through increasing water and soil salinity. This problem, mainly, affects the highly saline sensitive
species like Sonneratia apetala, Xylocarpus granatum, Heritiera fomes and Nypa
fruticans.
Though extensive areas of mangrove forest occur on sedimentary shoreline,
where large rivers discharge on to the low gradient coast, but excess input of sediments to mangroves can cause its degradation and death.
The other major threats to this ecosystem are reclamation of mangrove areas for
human habitation, aquaculture, agriculture, port and industrial and other developmental. One of the major human induced threats to mangrove ecosystem is its reclamation for shrimp aquaculture ponds. It accounts for the loss of about 20–50%
mangrove areas globally (Primavera 1997). Unauthorized felling and cutting of
branches of mangroves for fuel and fodder purpose often causes damage to mangrove ecosystem, however, the damage caused by this practice is not much significant. Dumping of sewage, solid and toxic wastes are the other kind of anthropogenic
threat to this vital coastal ecosystem.
Barge movement in rivers, resulting in the strong wave action, due to which
young regeneration/saplings get uprooted. This also leads to erosion on the river
banks.
Inadequate infrastructure for protection also poses some difficulties in mangrove
conservation but the threat to mangrove wetlands because of this problem is very
limited.
Ajai and H.B. Chauhan
eastern Africa. Mangrove’s three genera, namely, Acrostichum, Avicennia and
Rhizophora have the global presence (Spalding et al. 2010). More than 50 mangrove
species grow along the coast of Asia and that is the highest among all the continents.
Oceania region also supports more than 50 species of mangroves. Australia has
about 30 species. Africa has about 14 species of mangroves. South America as well
as North and Central America have only ten mangrove species (FAO 2007).
19.1.2 Threats to Mangroves
Despite the ecological and economic significance of mangroves they are considerably under pressure from human activities. Its area has declined by 30–50% in the
past 50 years, a higher rate than most other biomes (Balmford et al. 2002). It has
been estimated that the loss of world’s mangrove forest may be as high as 60% by
2030 (UNEP-WCMC 2006; Alonge 2002; Valiela et al. 2001). The major threats to
mangroves are:
Plantations and young plants are being damaged by the attachment of barnacles
to their stem. Insect attack also causes considerable damage to the leaves of various
species of mangroves like Rhizophora mucronata, Avicennia alba and Sonneratia
alba. Other species have also been found to be attacked by fungus.
Reduction in the quantity and periodicity of fresh water flowing into mangrove
wetlands affects the density as well as diversity of the mangroves through increasing water and soil salinity. This problem, mainly, affects the highly saline sensitive
species like Sonneratia apetala, Xylocarpus granatum, Heritiera fomes and Nypa
fruticans.
Though extensive areas of mangrove forest occur on sedimentary shoreline,
where large rivers discharge on to the low gradient coast, but excess input of sediments to mangroves can cause its degradation and death.
The other major threats to this ecosystem are reclamation of mangrove areas for
human habitation, aquaculture, agriculture, port and industrial and other developmental. One of the major human induced threats to mangrove ecosystem is its reclamation for shrimp aquaculture ponds. It accounts for the loss of about 20–50%
mangrove areas globally (Primavera 1997). Unauthorized felling and cutting of
branches of mangroves for fuel and fodder purpose often causes damage to mangrove ecosystem, however, the damage caused by this practice is not much significant. Dumping of sewage, solid and toxic wastes are the other kind of anthropogenic
threat to this vital coastal ecosystem.
Barge movement in rivers, resulting in the strong wave action, due to which
young regeneration/saplings get uprooted. This also leads to erosion on the river
banks.
Inadequate infrastructure for protection also poses some difficulties in mangrove
conservation but the threat to mangrove wetlands because of this problem is very
limited.
Ajai and H.B. Chauhan