Study Areas The study was conducted in different residing locations of the Rakhine community in Patuakhali and Barguna Districts under the Barisal Division of southern Bangladesh. Patuakhali and Barguna are 2 coastal districts of Bangladesh situated at the fringe of the Bay of Bengal. The coastal region of Bangladesh covers an area of about 47,201 km2 and its coastline is 710 km long and there live about 130 million people.32 The 2 study areas were subsequently divided into smaller study sites (S-1, S-2, S-3, S-4, S-5, S-6, S-7), where most of the Rakhine people live (Figure 1 and Table 1). The survey was performed in different locations of Kalapara Upazila (Patuakhali district) and Amtali Upazila (Barguna district). Survey areas were selected according to the maximum existence of Rakhine population in the areas. Kalapara Upazila is a local administrative region of Patuakhali district covering 483.08 km2 areas and lies in between 2148’ and 2205’ north latitudes and in between 9005’ and 9020’ east longitudes.
Kalapara Upazila is demarcated and delimited by Amtali Upazila on the north, the Bay of Bengal on the south, Rabnabad Channel, Galachipa Upazila on the east, and Amtali Upazila on the west.33,34 On the other hand, Amtali Upazila is a local administrative region of Barguna district covering 720.76 km2 areas and located in between 2151’ and 2218’ north latitudes and in between 9000’ and 9023’ east longitudes. It is bounded by Patuakhali sadar Upazila on the north, Bay of Bengal on the south, Galachipa and Kalapara Upazila on the east, Barguna sadar and Mirzaganj Upazila (Patuakhali) on the west. The study areas enjoy a tropical maritime climate characterized by high rain during monsoon. The study areas are characterized by calcareous alluvium, gray floodplain and grey piedmont soils. These types of soils are containing acid phosphate and are saline and the PH values are neutral to slightly alkaline. The study areas consist of coastal mangrove and wetland ecosystems and include both subtropical mixed evergreen and mangrove forests. Therefore, an abundance of mixed evergreen and mangrove plants can be seen throughout the study area. The most commonly found mangrove plants of this region are Barringtonia asiatica, Erythrina variegata L., Nypa fruticans, Sonneratia apetala, S. caselaoris, Avicennia officinalis, Excoecaria agallocha and Bruguiera gymnorrhiza e.t.c. Moreover, few representations of Heritiera fomes and Ceriops decandra were also noticed in the areas. In addition to the mixed evergreen plants like Albizia lebbeck, Cassia fistula L., Acacia nilotica, Borassus flabellifer L., Calotropis procera, e.t.c. are commonly found in the areas.
Sampling of Informants During the study period from April 2018 to June 2019 in separate seasons such as summer, monsoon, winter and spring, several repeated field trips were conducted to search for ethno-medicinal information from the Rakhine community in the study area. The investigation was done by adopting random interviews among the male and female informant members of the Rakhine community. Elderly Rakhine informants with age ranging from 45 years old to above were selected due to their vast traditional knowledge about the use of plant and plant products in their daily lives. The educational background and expertise in the use of traditional medicinal plants of the informants were also taken into consideration and priority was given to senior members of the family. A total of 41 individuals were interviewed in this study. They were mainly made up of elderly people from Rakhine tribes including the Traditional Health Practitioners (THPs) among the Rakhine community (Figure 2). The senior family members of the Rakhine community were asked to mention which plants they used and how they use it in curing diseases in daily lives. They were asked through field interviews, group interview guided field walks by receiving open-ended and semi-structured questionnaire (see Supplementary file) techniques according to Martin.36 To facilitate better communication and understanding, Bengali and Arakanese language were used which is made possible by the help of a local native language translator guide.
Data Collection and Identification For data collection in the survey areas, we first sought permission from the administrative authorities and later from the tribal chiefs of the Rakhine community. At first, it was clearly explained to the Rakhine informants about the objectives of the investigations because they did not want to disclose the information. The following information was collected by asking them according to the prepared questionnaire such as—(1) Rakhaine name of the plant (2) Habit (3) Plant parts used (4) Name of ailments (5) Mode of preparation e.t.c. They were shown photography of plants instantly downloaded from the internet using smartphones for local identification. The collected information and specimens were recognized, confirmed, and depicted up to species using different standard literature books37-39 such as the Encyclopedia of Flora and Fauna of Bangladesh published by Asiatic Society of Bangladesh.40,41 The plant species were identified further by consulting Prof. Dr. AHM Mahbubur Rahman, a taxonomist at the Department of Botany, Rajshahi University, Bangladesh. The plant scientific names have been checked with the different websites of plant database such as the International Plant Names Index, http://www.theplantlis t.org, https://www.mpbd.info. The samples collected, voucher specimens were prepared and more preserved at the Herbarium of Department of Botany, University of Barishal.
Data Analysis All types of primary field data of the bio-resources were analyzed and computed to determine the informant consensus factor (ICF), citation frequency (Cf) as well as preparing graphs, charts, etc. using Microsoft Excel spreadsheets following the mentioned statistical equations.