250
major threat to mangrove floral diversity in this sampling station. Harinbari and
Chemaguri are also located in the western sector of Sundarbans and experience the
negative impact of pollution of the Hooghly estuary. The station Lothian and Prentice
Island although located in the western sector of Indian Sundarbans and exposed to
Hooghly estuarine water exhibit maximum diversity index (H) values in all the
3 years. This may be attributed to their location within the Reserved Forest zone due
to which the human interference is minimum in these stations. The dilution factor of
the Hooghly estuarine water is also congenial for growth and survival of mangroves,
which is also another important factor contributing to the maximum diversity of
mangrove floral species in these sampling stations.
The true mangrove floral diversity values are relatively lower in the sampling
stations of central Indian Sundarbans (Sajnekhali, Chotomollakhali and Pakhiralaya).
This may be attributed to the synergistic effects of both hypersalinity and human
intrusion in these sampling stations, except Sajnekhali which is a protected Reserve
Forest under West Bengal Forest Department. The hypersaline water in the central
Indian Sundarbans is the effect of Bidyadhari siltation since the late 15th century
due to which the mangroves are less diverse and stunted in this zone.
The overall investigation thus pinpoints the hypersalinity and human intrusion as
the major threats to mangrove floral diversity of Indian Sundarbans and advocates
for an ecorestoration oriented management plan that encompasses (i) provision of
alternative livelihood to reduce the exploitation of mangrove resources (ii) increase
the dilution factor of the estuarine water through periodic dredging of the silted
Bidyadhari River and (iii) freshening the central Indian Sundarbans through construction of rainwater harvesting ponds and plantation of mangrove associate species in mass scale (as ground cover) like Sueada sp., Salicornia sp., etc. that are
potential absorber of salt from the ambient media.
In addition to true mangroves, mangrove associate floral species constitute an
integral part of mangrove biodiversity. The mangrove associates in the Indian subcontinent include various marsh grasses, sea grasses, sand binders and macro algae.
Spartina sp. is a common salt marsh grass (not documented in Indian Sundarbans)
which plays an important role in the replacement of mangrove vegetation through
competition. This particular marsh grass cannot survive in high salinities and fast
sediment accretion. As a result, it grows poorly in areas where mangrove thrive
(Kangas and Lugo 1990). This usually leads to its replacement by mangroves, as in
Paranagua Bay, Brazil (Lana et al. 1991). In Indian Sundarbans, the salt marsh grass
Porteresia coarctata is very common, which can tolerate a wide range of salinity
(Fig. 8.5).
However, due to habitat destruction, erosion (Fig. 8.6), human interference and
salinity fluctuation, the floristic species spectrum is presently under great stress.
A list of mangrove associate species commonly available in Indian Sundarbans
is highlighted in Table 8.5.
Sea grasses are associated with mangrove habitats in many areas. In the Andaman
Sea, there are three mangrove associated sea grasses Thalassira hemprichii, Enhalus
acoroides and Halophilus ovalis (Provachiranom and Chansang 1994). The only
sea grass found in intertidal mudflats of Indain Sunadrbans is Halophilus baccarii.
8 Mangroves: A Reservoir of Biodiversity
major threat to mangrove floral diversity in this sampling station. Harinbari and
Chemaguri are also located in the western sector of Sundarbans and experience the
negative impact of pollution of the Hooghly estuary. The station Lothian and Prentice
Island although located in the western sector of Indian Sundarbans and exposed to
Hooghly estuarine water exhibit maximum diversity index (H) values in all the
3 years. This may be attributed to their location within the Reserved Forest zone due
to which the human interference is minimum in these stations. The dilution factor of
the Hooghly estuarine water is also congenial for growth and survival of mangroves,
which is also another important factor contributing to the maximum diversity of
mangrove floral species in these sampling stations.
The true mangrove floral diversity values are relatively lower in the sampling
stations of central Indian Sundarbans (Sajnekhali, Chotomollakhali and Pakhiralaya).
This may be attributed to the synergistic effects of both hypersalinity and human
intrusion in these sampling stations, except Sajnekhali which is a protected Reserve
Forest under West Bengal Forest Department. The hypersaline water in the central
Indian Sundarbans is the effect of Bidyadhari siltation since the late 15th century
due to which the mangroves are less diverse and stunted in this zone.
The overall investigation thus pinpoints the hypersalinity and human intrusion as
the major threats to mangrove floral diversity of Indian Sundarbans and advocates
for an ecorestoration oriented management plan that encompasses (i) provision of
alternative livelihood to reduce the exploitation of mangrove resources (ii) increase
the dilution factor of the estuarine water through periodic dredging of the silted
Bidyadhari River and (iii) freshening the central Indian Sundarbans through construction of rainwater harvesting ponds and plantation of mangrove associate species in mass scale (as ground cover) like Sueada sp., Salicornia sp., etc. that are
potential absorber of salt from the ambient media.
In addition to true mangroves, mangrove associate floral species constitute an
integral part of mangrove biodiversity. The mangrove associates in the Indian subcontinent include various marsh grasses, sea grasses, sand binders and macro algae.
Spartina sp. is a common salt marsh grass (not documented in Indian Sundarbans)
which plays an important role in the replacement of mangrove vegetation through
competition. This particular marsh grass cannot survive in high salinities and fast
sediment accretion. As a result, it grows poorly in areas where mangrove thrive
(Kangas and Lugo 1990). This usually leads to its replacement by mangroves, as in
Paranagua Bay, Brazil (Lana et al. 1991). In Indian Sundarbans, the salt marsh grass
Porteresia coarctata is very common, which can tolerate a wide range of salinity
(Fig. 8.5).
However, due to habitat destruction, erosion (Fig. 8.6), human interference and
salinity fluctuation, the floristic species spectrum is presently under great stress.
A list of mangrove associate species commonly available in Indian Sundarbans
is highlighted in Table 8.5.
Sea grasses are associated with mangrove habitats in many areas. In the Andaman
Sea, there are three mangrove associated sea grasses Thalassira hemprichii, Enhalus
acoroides and Halophilus ovalis (Provachiranom and Chansang 1994). The only
sea grass found in intertidal mudflats of Indain Sunadrbans is Halophilus baccarii.
8 Mangroves: A Reservoir of Biodiversity