Despite the significant ecological and economical services, mangroves have witnessed an annual loss between 0.16 and 0.39%, globally, due to rapid coastal development . In south Asia (also known as Indian Subcontinent), mangrove forests have been lost at an average rate of 0.18% per year . In India mangroves are spread over an area of 4921km2, which representing 3.3% of the global mangrove vegetation . In contrast to global trend, in India mangrove extent has increased in last decade. The estimates of Forest Survey of India show a net increase of 875km2 during 1987-2017 when the mean annual change in mangrove extent was 30.21±81.72km2; the extent of increase was 112km2 between 2013 and 2015 and 181km2 between 2015 to 2017 .
However, the global mangroves, as well as in India, have witnessed the implicit species loss despite mangrove expansion in many regions [1,4,5]. This calls for the evaluation of our understanding on mangrove dynamics and effectiveness of existing conservation methods and a refinement in them for better management of mangroves. Considering these facts in this text status of Indian mangroves have been discussed.
Mangrove forests in India are found along the coastline of 9 States and 4 Union Territories and it is the third richest country in the world in terms of mangrove species diversity with 46 true mangrove species belonging to 14 families and 22 genera . However, the species diversity of Indian mangroves is under constant flux due to both natural (e.g. erosion, aggradations) and anthropogenic forces, possibly leading to changes in floristic composition and local extinction of some species. For instance, certain mangrove species viz., Heritiera littoralis, Xylocarpus granatum, Bruguiera cylindrica, Lumnitzera racemosa, Sonneratia caseolaris and Cynometra iripa are on the verge of extinction in the west coast [7,8].
In east coast, the extent of Heritiera fomes, is estimated to have declined by 76% since 1959 and about 70% of the remaining H. fomes trees were affected by the ‘top dying’ disease . Further, the populations of Nypa fruticans, and Xylocarpus molluccensis also underwent dramatic declines in Indian Sundarban .
Selvam  did not observe Xylocarpus granatum, Sonneratia apetala, Kandelia candel and Bruguiera gymnorhiza in Pichavaram mangroves, which were two decades earlier, from the region. About 52% of mangrove species in India have restricted distribution  and 9 species are of conservation significance at global level - Sonneratia griffithii and Heritiera fomes are ‘critically endangered; Excoecaria indica and Aglaia cucullata are ‘data deficient’; Aegialitis rotundifolia, Brownlowia tersa, Ceriops decandra, Phoenix paludosa and Sonneratia ovata are ‘near threatened’ . In addition, mangrove floristics of mainland India not explored sufficiently in recent times.
Thus, species identity and distribution remains elusive in mangroves of mainland India. For instance, identity and distribution of Sonneratia griffithii in Sundarban and Odisha, Acanthus ebracteatus in Kerala and Odisha, Avicennia Alba in Kerala and Rhizophora stylosa in Odisha are not clear. Further, certain species like Aglaia cucullata, Bruguiera sexangula etc., are not found in the field more than decade. So the extensive floristics studies are precise to provide the correct identity and distribution of mangroves in East and west of India. Furthermore, efforts would be taken to increase the population of species under the risk of extinction or of low abundance.
Information of forest structure is the primary database that provides insight into the specific feature of each mangrove ecosystem. Mangrove stands exhibit wide regional and local variation in their structural characteristics as it is controlled by local site factors including topography, soil properties, and tide fluctuations [13,14] than the climatic factors like rainfall and temperature, which controls the worldwide distribution of mangroves.
Hence, understanding local level forest structure is highly essential for their management. But in Indian context, studies on mangrove forest structure are very limited. Forest structural studies on Indian mangrove forests at Pichavaram and Muthupet [15-17], in Andaman Islands [18-23], in Odisha [24,25], in Andhra Pradesh [26-29], in Kerala [30-35], in Gujarat  and in Sundarbans [37-44] are noteworthy. Complexity index (Ic) and Important value index (Iv) are the structural indices often used to
express existences of stress in the forest stand and importance of
a tree species within a stand of mixed species respectively. Based
on the available literature, it is event that except ANI, all other
mangrove habitat in India has low Ic value and Avicennia marina
constitutes the important tree species, whereas ANI exhibit
high Ic value and Rhizophora species constitutes the important
tree species. The low IC value indicating the low structural
development and prevalence of disturbances in these mangrove
Further abundance of Avicennia species indicates the
prevalence of high saline condition in Indian mangrove habitat.
Thus, despite the high species richness, species of low saline
tolerant have restricted distribution. Abundances may decline
long before the species richness does and so the species of
low abundance should be given high conservation priority.
Furthermore, mono-specific stands may have low thresholds for
perturbations and be thus more vulnerable to environmental
changes e.g. attack by diseases, drought, sedimentation, and
flooding, among the stresses.
In recent times it has been understood that mangrove
associated fauna play such a significant role to shape the mangrove
forest structure and the functioning of the ecosystem [45-49].
Sediments, root structures and large woody debris are the three
main substrata that fauna are able to exploit in mangroves [45,50-
53]. The faunal communities in mangroves chiefly consists of
terrestrial (insects, birds, mammals and reptiles), aquatic (fish,
crustaceans, molluscs and echinoderms) and benthic animals
(polychaetes, brachyuran crabs, wood-boring animals, mud
burrowing bivalves, gobiid fish, gastropods and some sessile
bivalves, such as oysters, Modiolus spp. and barnacle crustaceans
. However, faunal assemblages of mangroves are significantly
less studied and documented than the forests they inhabit.
Mangrove forest ecosystems in India support diverse groups
of fauna comprising of 3091 species. This is perhaps the largest
biodiversity record in world mangrove ecosystems . Invertebrates
are greater in number of species than vertebrates. The
faunal species so far recorded were highest (2061) in the mangroves
of the east coast, followed by 922 species in Andaman and Nicobar
Islands and 727 species on the west coast. In recent times faunal
diversity in different sites of Indian mangroves has been studied
[56-62]. However, the knowledge on faunal assemblage in Indian
mangroves is far from complete and it significances in shaping the
forest structure and ecosystem functioning is not determined due
to lack of consistent in quantitative data.
The population structure and distance over which gene flow
occurs can inform management decisions regarding conservation
and management of threatened ecosystems . Since mangroves
are at elevated risk understanding of genetic status and the degree
of divergence among populations is a necessary for successfully
preventing their extinction [64,65]. It was previously assumed that mangroves are genetically undifferentiated throughout its
range due to long-distance oceanic dispersal of these propagules
However, experimental studies and recent molecular studies
showed that strong genetic differentiation between populations
of many mangrove species – Ceriops tagal and C. decandra
, Lumnitzera racemosa [69,70], L. littorea , Rhizophora
apiculata , Sonneratia caseolaris  and S. alba . Except
few regional specific studies [75-82], population structure
of Indian mangroves has not been studied much. Patterns of
genetic affinity and differentiation are generally explained by the
presence of barriers in the landscape matrix, which may delay
or hamper dispersal, and by testing the isolation-by-distance
(IBD) model. Recent studies indicate the role of ocean currents,
geomorphology, and hydrology of the estuary and water surface
currents in shaping the population structure of mangrove species
[83-86]. Furthermore, recent studies shown the low genetic
diversity in the wide spread mangroves species of the world .
So understanding of regional specific population structure is
desired for better understanding of current distribution pattern
of mangrove species and conservation measures.
Biodiversity and ecosystem functioning of mangroves is
determined by species composition and forest structure [88,89].
Since species diversity and distribution and forest structure
of mangroves are variable in different spatial scales (i.e.,
global, regional, estuarine and intertidal), the ecological and
socioeconomic benefits offered by mangroves are also variable
between the region. So without site specific knowledge, it is
imprecise to quantify the economic value of mangroves on broad
scale at global level. In the last three decade various efforts have
been taken to restore the degraded mangroves. However, many
efforts have been documented to result in big failures in achieving
the desired level of mangrove restoration due to poor species
selection. In India, most of the mangrove restoration programmes
were intended only to increase the area coverage and most
afforestation efforts have been carried out with Avicennia species,
with low or high survival rates.
On the whole in India mangrove cover has witnessed
increasing trend and the number of mangrove taxa has also
increased slightly on documentation since the mid-1980s, but
their populations have not been tracked along the same trajectory.
In the past, the conservation programmers for mangroves have
largely been conducted with the lack of comprehensive speciesspecific
information and often aimed to increase the area. In
terms of mangrove conservation, only mangrove areas were
rehabilitated, wherein ecological and economical services could
not be fully restored. Since mangroves are present in land-sea
transition zone, their natural extension is limited by urban
development in landward side and sea level rise in seaward side.
The primary threats to all mangrove species are habitat
destruction and removal of mangrove areas for conversion to aquaculture, agriculture, urban and coastal development, and
overexploitation. Further, reduction in freshwater, nutrient
enrichment through sewage discharge and sea level rise also
threatened the mangrove species particularly low saline tolerant
species. It is also pertinent to rejuvenate the species under
significant threat (e.g. Sonneratia griffithii, Brownlowia tersa),
especially those requiring stringent environmental conditions,
like low salinity to grow (e.g. Heritiera fomes, Nypa fruticans
etc,). Considering the low species richness and low genetic
diversity it is imperative to assess the site specific information of
mangroves to prevent it extinction. The contemporary mangrove
conservation regime also advocates “early detection and preemptive
rehabilitation”, for successful management. And to
achieve this, location-specific and species-specific information on
the mangrove stands are the prerequisites , without which
world without mangroves  will be a distinct possibility in the