Indian Journal of Geo Marine Sciences Vol. 48 (04), April 2019, pp. 504-510

Mangrove vegetation change in Vagra Taluka, Bharuch district, Gujarat, India from 1978 to 2012

Shreestuti S. Khare & Dharmendra G. Shah* Department of Botany, Faculty of Science, The Maharaja Sayajirao University of Baroda, Vadodara, Gujarat. *[E-mail: [email protected]]

Received 08 September 2017; revised 09 January 2018

Mangrove forests are an important and unique ecosystem found along the intertidal zones of tropical and sub-tropical regions. The present paper deals with the change in the distribution, density and areal spatial extent of mangroves over a period of 39 years for Vagra taluka in Bharuch district (Gujarat, India), using remote sensing. The results show an increase in the areal extent and density of mangroves from 147.61 ha in 1978 to 1013.82 ha in 2012. The overall increase in the mangrove cover however masks the dynamics of change in the distribution and extent of this category. Approximately, 514 ha of mangroves were degraded during the period 2001 to 2012. Conversion into salt pans was the largest cause for destruction of mangroves during the period while natural causes like erosion and due change in the course of Dhadhar River also contributed to loss in mangrove areas.

[Keywords: Mangrove; Change detection; Bharuch]

Introduction tremendous pressure on this ecosystem. A study of the Mangroves are considered to be one of the most mangroves ecosystem and its various attributes productive and biodiverse wetlands on earth.1,2 They requires a large variety and quantum of data. are a group of highly evolved halophytes occupying Conventional methods require a lot of time, effort and the intertidal zone in estuaries, lagoons and coastal funds and present information of only a small area, mudflats along tropical and sub-tropical coastlines. whereas optical remote sensing with its synoptic, Till about the 1960s, mangroves were largely viewed multispectral and repetitive coverage is very useful in as “economically unproductive areas” and were the study of mapping mangrove areas, biomass therefore destroyed for reclaiming land for various estimation, its association with other plant economic activities.3 Though, the economic and communities and changes in their conditions, through ecological advantages of mangroves are now known time and space.7 In the last few years, considerable and their importance appreciated, their full value is work has been carried out in mapping and assessing still not recognized in most countries, as most of these mangrove ecologies along the coastal regions of the benefits are not direct. Consequently, mangroves have world using remote sensing techniques8,9,10,11,12,13,14 remained a highly neglected ecosystem, resulting in and in the field of change detection analysis.15,16,17,18 its heavy depletion and degradation in most parts of Change detection is the process of identifying the world.4 India with a coastline of about 7500 km differences in the state of an object or phenomenon by currently harbours 4740 sq km area of mangroves.5 observing it at different times.19 In India, several According to the Forest Survey of India (FSI), the workers have carried out studies on change detection mangroves of India have shown a major improvement analysis with special emphasis on the during 2013 to 2015 after a marginal reduction from mangrove.16,18,20,21 Several government and academic 2011 to 2013.5 In India, Gujarat stands second after organizations prepare land use land cover maps for West Bengal in the areal extent of mangrove different parts of the country in a variety of vegetation, which covers about 1107 sq km.5 The scales.22,23,24 These maps provide basic information on major mangroves in the state are located in the Kori mangrove cover and a comparison of these maps of Creek, Gulf of Kachchh, Porbander in Saurashtra, different dates provides information on change in the Gulf of Khambhat, and in South Gujarat.6 Large scale mangrove cover over a specific time period. These developmental activities along the coast have put a maps however, do not directly provide information on KHARE & SHAH: MANGROVE VEGETATION CHANGE IN VAGRA TALUKA BHARUCH DISTRICT GUJARAT 505

either the exact locations or the classes from where Khambhat and on northern and southern sides by the changes have occurred. These change dynamics Dhadhar and Narmada estuaries. The annual rainfall are very important for understanding the cause of received in the taluka during 2003-2013 was 969 mm these changes as well as their management. Change while the temperature ranged from 10.2 to 42C.26 detection studies give qualitative as well as Geomorphologically, the area is characterized by vast quantitative information about the dynamics of the tidal mud flats on the western side and a narrow strip changed categories and provide insights into the on the southern side of Vagra taluka. The intertidal factors responsible for degradation or improvement of expanse in this region ranges from 2 to 3 km in width the mangrove vegetation. Thus, such studies have an and numerous small to medium sized creeks having important role in the management and conservation of an average depth of 4-5 m dissect the intertidal region. this important coastal ecosystem. Bharuch district in In the recent past, Vagra taluka has become a hub for Gujarat has also seen large-scale changes in the extent various industries which has lead to substantial changes of mangrove vegetation and the current study in land use and land cover of the area.27 investigates the change dynamics of the mangroves Materials and Methods along Vagra taluka of Bharuch district using remote Historical data of the area was obtained from the sensing data and field observations.

Survey of India (SOI), topographic sheet index 46C/9, Vagra taluka, located in Bharuch district in the 46C/10, 46C/13 and 46C/14 having scale of 1:50,000 south central Gujarat, India, constitutes a marginal and surveyed during 1973-74. The satellite data for strip of the southern Gujarat alluvial plain. It falls 1978 (Landsat MSS) and 1987 (Landsat TM) was between 21 37’ N to 21 57’ N latitude and 72 30’ E downloaded from the United States Geological Survey to 72 54’ E longitude with a total geographical area (USGS)-GLOVIS website (http://glovis.usgs.gov/). of 88,342.64 ha.25 and has 68 villages (Fig. 1). The Whereas satellite images for 1997 (IRS 1C LISS III), area is delimited on the western side by Gulf of 2001 (IRS 1D LISS III), 2004 (IRS P6 LISS III) and

Fig. 1 — Location map of Vagra taluka 506 INDIAN J. MAR. SCI., VOL. 48, NO. 04, APRIL 2019

2012 (IRS P6 LISS III) were procured from National Results and Discussion Remote Sensing Center (NRSC), Hyderabad. For Avicennia marina (Forssk.) Vierh. is the only preparing the mangrove cover maps ERDAS species of true mangrove found in the area. A IMAGINE (V 9.1) software was used. The comparison of the analyzed data over 39 years classification system developed at the Space indicates a major change in the mangrove cover in Application Centre, Ahmedabad, was used with some terms of its density, areal extent and distribution. modifications.28 The mangrove cover maps were During 1973-74, they were present only on the prepared using the same methodology as has been southern side of Vagra taluka. A major change in the described in Tattu et al.22 The analyzed map of 2012 distribution of mangroves from the South to the west was selected as the pre-field map. This map was and north west of the taluka was observed during this verified on ground during several field visits and period. The mangrove cover of the taluka showed an necessary modifications were incorporated. The increasing trend in areal extent over this period except accuracy of the classified maps was determined during 2004 where a substantial reduction was noted. through the method given by Congalton.29 In the The area covered by different mangrove density classes present study, the post-classification change detection as well as the total area for all the years investigated is method was followed where thematic maps of given in the Table 1. Thematic maps showing different years were compared to bring out the mangrove cover for the years 1973-74, 1978, 2001 and changes in the mangrove cover over a period of time. 2012 are given in Figure 2. The classification accuracy The thematic maps of 1978, 2001 and 2012 were used of the classified maps was estimated to be 84%, 88%, to bring out the change in the mangrove during 88%, 86%, 85% and 90% for 1978, 1987, 1997, 2001, 1978-2001 and 2001-2012. Software ARC Info 7.2.1 2004 and 2012. The change detection study resulted in and the procedure given by Shah16 was followed. a large number of changed categories.

Fig. 2 — Mangrove cover in Vagra taluka over a period of time KHARE & SHAH: MANGROVE VEGETATION CHANGE IN VAGRA TALUKA BHARUCH DISTRICT GUJARAT 507

To make these changes in the mangrove categories vegetation colonization occurred in 561.34 ha, while more comprehensible, the changes were grouped into there was a loss in 108.63 ha; whereas during three broad groups which broadly indicated no 2001-2012, colonization occurred in 732.18 ha while change, mangrove improvement and mangrove these was a loss in 355.45 ha. This indicated an degradation areas. Figures 3 and 4 shows the change increased pressure on the mangrove ecosystem during in mangrove vegetation over 1978-2001 and the later period of the study. Density-wise 2001-2012 respectively while Table 2 shows the improvement was 17.94 ha, and 40.19 ha whereas change in areal cover for different categories. degradation was observed in 5.62 ha and 158.74 ha Keeping changes in density aside, the 1978-2001 during the periods 1978-2001 and 2001-2012, change analysis indicated that new mangrove respectively. The improvement of mangrove area was

Table 1 ─ Areal extent of different mangrove density classes of Vagra taluka from 1978-2012 Area (in ha) for the year Class Name 1978 1987 1997 2001 2004 2012 Very dense mangrove 0.00 2.02 5.56 145.13 79.96 111.39 Dense mangrove 23.10 63.20 98.84 185.37 83.29 351.63 Sparse mangrove 161.28 82.38 307.99 306.60 257.58 550.80 Total 184.39 147.61 412.39 637.10 420.83 1013.82

Fig. 3 — Change in mangrove cover during 1978-2001 Fig. 4 — Change in mangrove cover during 2001-2012 508 INDIAN J. MAR. SCI., VOL. 48, NO. 04, APRIL 2019

Table 2 ─ Areal extent of mangrove changed categories Categories Sub Categories 1978-2001 2001-2012 (Changed & Unchanged) Area (in ha) No Change Very dense mangrove 0.00 3.12 Dense mangrove 7.54 9.50 Sparse mangrove 44.66 70.11 Total 52.20 82.72 Improvement Mudflat to mangrove 552.82 709.93 Density wise improvement in mangrove 17.94 40.19 Salt marsh to mangrove 5.34 4.70 Water body to mangrove 3.18 17.54 Total 579.28 772.37 Degradation Density wise degradation in mangrove 5.62 158.74 Mangrove to salt marsh 22.99 87.24 Mangrove to mudflat 84.13 95.67 Mangrove to water body 1.37 62.20 Mangrove to industry 0.13 110.35 Total 114.25 514.19 due to their growth on the barren mudflats and even mangroves in 2004. Several oil wells located to the in the salt marsh zone. The colonization of water south of Aladra village were also lost due to this erosion. body was mainly on account of its growth along the Conclusion creeks. Natural growth and good regeneration 30 The distribution of mangrove cover in the study has capability of Avicennia marina (Forssk.) Vierh. and changed in addition to an increase in areal extent. the plantation activity taken up by the state forest This increase has been due to natural regeneration on department and several other organizations were the account of the feasible environmental condition as major reasons for increase in the mangrove cover of 31,32 well as plantation activity by several organizations. the district. Destruction of mangrove vegetation The change detection analysis highlights the highly and its conversion to industries was the biggest cause dynamic nature of the mangrove vegetation. The role for degradation after density change. Also an analysis of the saltpan industry and the role and severity of of the sites where mangroves had been converted to erosion in mangrove degradation is also highlighted in mudflats points to their close proximity to industries the study. This degradation of mangroves was (Fig. 4). Thus industrial development not only played however masked under the increasing trend of a direct role in mangrove loss, but it was also mangrove cover of the district. Such studies are thus indirectly responsible for its loss in the vicinity. essential to understand the impact of natural and Saltpans industry mainly developed in the intertidal anthropogenic influences on mangrove ecosystems. areas and was mainly responsible for the degradation of mangroves. The destruction of mangroves due to Acknowledgement the development of saltpans has been reported in The authors acknowledge the Space Application several parts of the world including India.33,34,35 This Centre (SAC), ISRO, Ahmedabad, for providing industry has occupied most of the barren intertidal funds in the initial stage of the study. They mudflat area (Fig. 2 – Year 2012) and any further acknowledge the Coastal Zone Management expansion would be at the cost of either mangroves or Authority (CZMA), Government of Gujarat, for salt marsh vegetation. providing satellite image of the year 2012. They also A closer look at Table 2 indicates that conversion acknowledge USGS (Glovis) for providing the free to water bodies was also responsible for loss of satellite images for the current study. The authors are mangroves. The change in the flow of Dhadhar River also thankful to Departmental Research Support has resulted in high erosion along the north-western (DRS), UGC, for help in carrying out the field work region (especially west to Paniyadra village) of the during the later part of the study. taluka. The intensity of erosion was so high that References mangroves which generally have a high resistance to 1 Odum, W.E., McIvor C.C., & Smith T.J., The Ecology of the erosion were also eroded along with the mudflats. Mangroves of South Florida: A Community Profile. A final This was the main reason for the reduction of report by the U.S. Fish and Wildlife Service for the U.S. KHARE & SHAH: MANGROVE VEGETATION CHANGE IN VAGRA TALUKA BHARUCH DISTRICT GUJARAT 509

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