Sundabarns Flashcards
Briefly describe the location and extent of the Sundarbans coastal zone
Extends over 10,000km2 of southern Bangladesh and India on the Bay of Bengal.
Identify two natural features of this unique coastal landscape
• The world’s largest delta.
• Extensive mangrove forest – the climatic climax vegetation
Name the rivers that feed into the delta
• Ganges
• Brahmaputra
• Meghna
Identify the natural processes that have a role to play in creating this coastal landscape
• Deposition
• Tidal processes
• Marine erosion
• Aeolian (wind) transport and deposition
Outline the role played by deposition in the formation of this landscape
• The three rivers, including the Ganges, carry large amounts of fine sediment (silt and clay) which is deposited when the rivers lose energy as they approach the Bay of Bengal.
• As the sediment builds up over time it forms mounds or islands in the river channels. This has created a network of interconnected channels flowing round islands of sediment. The small channels are called khals.
• The position of the islands and channels remain relatively stable as the silt and clay is quite cohesive and resistant to erosion.
Outline the role played by tidal processes in the formation of this landscape
• The delta is tidal. Twice a day at high tide saline water washes northwards into the delta and then at low tide water washes southwards back towards the Bay of Bengal.
• This regular tidal flow has led to the development of larger (up to 2km wide), straight channels in the delta running north-south.
• The larger channels are connected to each other by the smaller khals.
Outline the role played by aeolian processes in the formation of this landscape
• Whilst fine silt and clay is deposited by the river in the delta, coaster, less cohesive sand is carried further towards the mouths of the channels nearer the coastline.
• Some of the sand builds up on the banks to form chars.
• Where the sand dries out, when it is above the waterline, it
is picked up by the south-westerly Monsoon winds and transported inland where it is deposited to form sand dunes over time.
Outline the role played by vegetation succession in the formation of this landscape
• As sediment builds up over time in the delta the islands will remain above the water under normal condition.
• Vegetation succession will take place beginning with salt tolerant (halophytic) pioneer species and progress to the climatic climax vegetation, mangrove forest (if not
interrupted by human activity or natural disaster).
• Once established the root system of the mangrove trees
will further stabilise the islands of sediment, help prevent
erosion and trap more sediment over time.
• Vegetation succession will also occur on the sand dunes, stabilising the chars and providing more protection resulting in increased deposition in the river channels behind and the formation of more islands.
Identify three goods provided by the mangrove forest and outline how they provide economic or environmental opportunities for people
• Wood from the forest can provide fuel for heat and cooking, for furniture and construction (including thatch for rooves).
• Natural poison and floats help in the catching of fish which is also an important food source.
• The rich ecosystem provides many food items including crab, shrimp, honey, leaves, and fruit.
• Commercial products include textiles from furs and skins, natural dyes, wax, glue, medicines and paper.
Outline three services that the mangroves provide for people and outline the environmental and economic benefits
• The forest provides protection from flooding and cyclones.
• The forest is an important carbon sink and sequesters
around 4 billion tonnes of CO2 a year.
• The forest provides nursery grounds for fish which helps
maintain the natural ecosystem.
• The forest has value for ecotourism, education, and
scientific research as well as for cultural, spiritual, and religious reasons.
Identify three key risks for people living in the Sundarbans and outline the challenges they pose
• Royal Bengal tigers are becoming an increasing risk because of decreased habitat due to deforestation and increased population growth.
• Coastal flooding in the Bay of Bengal due to eustatic sea level rise (enhanced greenhouse effect and thermal expansion) is resulting in higher levels of salinity in the soil making agriculture difficult and affecting freshwater drinking supplies.
• More intense cyclones in the Bay of Bengal due to higher sea surface temperature increase the risk of erosion, flooding, and damage to the forest and well as increasing the risk to people and property.
• Coastal resources, including the forest and fish, are being over-exploited due to a growing population and more destructive fishing techniques. Wetlands are being converted into agricultural land leading to a loss of biodiversity.
Identify three ways in which the people of the Sundarbans are adapting to the challenges they face
• Salt tolerant varieties of rice – these have been introduced to cope with the increased salinity of the soil due to saltwater intrusion.
• NOGs are building latrines on higher ground to avoid contamination of the water supply during floods.
• USAID have trained 30,000 people in the use of improved agricultural techniques more suited to the conditions caused by climate change.
• Storage tanks for rainwater are used to protect supplies in areas as risk of saltwater inundation.
• Cyclone shelters are becoming multi-purpose e.g., used as primary schools.
Outline two examples of resilience shown by people in the face of the challenges faced
• The mangrove forest allows people to be resilient in the face of a storm – a density of trees of 30 per 0.01 hectares can reduce the destructive force of a cyclone by up to 90%.
• The mangroves also provide a wealth goods and services - giving a range of options in the face of change e.g., the natural fertility of the soil and ecological diversity provide a range of nutritious foods.
• When only used for traditional activities, the forest has an economic value of $12,000 per hectare (fishing, timber, tannin, and seafood).
Outline two examples of mitigation in the face of the challenges posed by climate change
• Community access to natural resources on khas land (government owned land protected for use by local populations) as well as access to the forest and fishing.
• Significant investment in infrastructure, such as cyclone shelters, flood protection and tube wells (to reach fresh ground water stores).
• NGOs and the government have provided micro-credit for businesses which provides an economic safety net.
• Afforestation of mangrove forest on some islands.
Identify reasons why the resilience of local people is being eroded over time and why mitigation strategies may be insufficient.
• The forest ecosystem continues to be degraded in many areas, reducing the level of protection it provides and the range of goods and services it offers. This is due to continued population rise and loss of land due to erosion and over exploitation of resources.
• Open access areas, including khas lands) are shrinking over time.
• The number of deaths from tiger attacks in increasing over time.
• Sea levels continue to rise, and the threat of cyclones increases as global temperatures continue to rise due to the enhanced greenhouse effect.
