Title : Geo-information for conservation strategy of archaeological heritages in an Alluvial Terrain (Bangladesh) in the context of climate change
Bangladesh is one of the worst affected countries of the world by human induced global warming and climate change because of its unique geographic and geologic locations, dominance of flood- and deltaic plains formed by dynamic river system, low elevation from sea, high population and density, substantial dependence on agriculture, and poverty (worsen by Covid-19 pandemic). Climate change have impact not only on water resources, agriculture, health, coastal zones and ecosystem but also on land resources which house its rich archaeological sites and cultural heritages. Its geology and geomorphology favour development of human settlement since long like other parts of the globe. Early human occupations in this country thought to be of pre-historic (paleolithic, mesolithic and neolithic) period developed in the hilly areas of eastern, northeastern and mid-northern parts. The humans changed habitational sites and styles through time with changes in behavioural characteristics and adaptation capability. Settlements dated about two thousand four hundred years and later periods developed on the uplifted terraces in the middle, eastern and north-western parts of the country. Later habitations started on Recent floodplains when the landform became habitable because new environment offered fertile land favourable for agriculture, suitable and well connected riverine communication system, potable water, construction materials with sites of dwellings and defence. Human migrated towards the coastal region of the country few hundred years ago probably for the emerged opportunity of trade and communication as well as improved knowledge. Climate change manifested by temperature increase, sea level rise, salinity intrusion, desertification in some region, changes in precipitation pattern and humidity; extreme weather events, natural hazards etc. will affect the archaeology in two ways -- the site on which the structure is sitting i.e. geomorphology and materials and processes, and the structure itself. Another factor namely, climate migrants will place extra impact on the situation. Geomorphology of Bangladesh can broadly be divided into five major divisions – flood, deltaic and coastal plains; slightly elevated flood and deltaic plains; uplifted terraces; hills; and wetlands. Geologically, eighty percent of the surface and near surface of the country is covered with floodplain and deltaic Holocene sediments consisting of unconsolidated sand, silt and clay of varying amounts, and are the products of piedmont, alluvial, fluvial, deltaic or coastal processes. Eight percent area is covered with uplifted terraces composed of Pleistocene Clay Residuum whereas rest 12% area is occupied by hills consisting mainly of folded sandstone, siltstone, shale and clay of Tertiary age. Regional active tectonics, continues till today since Miocene, has control on geology, shaping the delta surface and sediment distribution rate and pattern, and river courses. Now it is clear that operating processes, ages of the geomorphological entities and their constituent materials are different having varied mineralogical, physical and chemical properties. All these will behave differently with different intensity under changed climate scenario along with anthropogenic pressure. Thus geo-information about the archaeological sites would act as an aid to conservationists to formulate the strategy for management of our archaeological and cultural heritages.