Adrift along the Sundarbans mangroves, east India

Mid March 2021, I set out with 2 other wildlife enthusiasts to explore the Sundarbans delta in east India. The 3-hour journey from Kolkata city, on a busy road fringed by industrial towns tapered off at Gadkhali port – civilization’s last ‘land’ frontier before the largest  continuous mangrove stretch in the world. We arrived after dusk, boarded our boat (with a crew of 2 naturalists, 3 boatmen, and a chef!), and were adrift upon dark waterways guided by twinkling village lights. In our haste, we thought little of just how ‘remote’ this wilderness was. 

The next morning, we woke up to a different world – sheer, open stretches of water that melted away into the morning haze. Nothing quite prepares you for the Sundarbans, one imagines river deltas as narrow channels of water interrupted by little islands, yet that morning, with no other islands visible on the horizon, it seemed more like a sea than a river. For the next three days, we’d be exploring the Sundarbans – among the most difficult terrains for civilization and wildlife watching, from dawn to dusk. 

A stand of 'sundari' trees (Heritiera fomes) with a distinct line of discolouration marking the high tide line.
A stand of ‘sundari’ trees (Heritiera fomes) with a distinct line of discolouration marking the high tide line.
Photo credits: Devayani Khare

Formed as several rivers, including the Hooghly, Ganges, Brahmaputra, Meghna, and other channels with different local names, combine and flow towards the sea. The Sundarbans named for the ‘sundari’ trees (Heritiera fomes) + ‘ban’ the local word for forests, covers roughly 10,000 sq. km (3900 sq. miles), partly in India and partly in Bangladesh. Of the delta’s 104 islands that fall within India’s territory, just a handful of islands are inhabited, while the rest form the buffer and core zones of the Sundarbans National Park. With its incredible, fragile biodiversity, the Sundarbans was also declared a UNESCO World Heritage Site in 1987.

As idyllic as remote islands seem, the Sundarbans has always been a dangerous landscape, and not just on account of the tigers. Rapid coastline erosion, riverbanks and islands shape-shift due to the accumulation or removal of sediment or silt, and extreme events like cyclones are commonly experienced in the Bay of Bengal [1] – the sea that the delta opens out into. Cyclones like Amphan (May 2020), Fani and Bulbul (both 2019) were among the 13 supercyclones this area has witnessed in the past two decades [2]. Research across the world has shown that dense mangrove vegetation reduces the wave height and wave energy during storms[4], and can thereby dampen the effect of extreme events like storms and cyclones.  Yet, deforestation has thinned out the ‘protective shield’ of mangrove, and the ‘sundari’ trees which the forests were named after have been declared endangered by the IUCN. 

There is less than a century’s worth of geoscience research available for the region, and it indicates that the delta is in constant flux: sediment building and eroding away at its banks. This makes embankments and other coastal engineering solutions unviable, and farming is a poor prospect[3]. Rising sea-levels caused by climate change may further fragment the habitat and cause greater salinity in the water, both of which will adversely affect the fauna and flora. The short data record makes it difficult to understand long-term cycles for better mitigation in the near future.

A partly leucistic i.e lacking skin pigment, saltwater crocodile (Crocodylus porosus) basking along the banks - crocodiles and tigers account for most of the human-wildlife conflicts in the Sundarbans.
A partly leucistic i.e lacking skin pigment, saltwater crocodile (Crocodylus porosus) basking along the banks – crocodiles and tigers account for most of the human-wildlife conflicts in the Sundarbans.
Photo credits: Devayani Khare

For locals, livelihood options are limited: near-subsistence farming or fishing (saltwater fish, shellfish, and crabs), boat-operated trade with the mainland, timber-felling (most of it illegal), honey, fruit, resin and medicinal plant extraction governed by the forest authorities and forest range services with a high risk of man-wildlife conflicts. Fly ash trade with Bangladesh flourishes, but as Kolkata is the major hub of operations with the Sundarbans merely a thoroughfare, there are few local job opportunities. However, in recent years, tourism within the delta has emerged as an economic champion: encouraging private investment in infrastructure, accelerating development with over 30 hotels and resorts ranging from economic to luxury, and the promise of further expansion.

Yet tourism development is a two-edged sword: in India, it has often been blind to the carrying capacity, local needs, and risks of a destination. The recent, mid-March 2021 election drive saw promises being made by the central government – Rs 2 lakh crore/trillion (that’s over 13 billion USD!) investment to develop the Sundarbans into the most advanced region in the West Bengal state. Even if this is empty political rhetoric, development of the Sundarban delta is an imminent threat – as not all of it will consider the ecological role of mangroves, the complexities of sediment transfer, the storm-dampening effects nor the local socio-economic and political context.

A crested serpent eagle (Spilornis cheela) is one among many raptors that haunt the mangrove stretches in search of snakes and lizards.
Photo credits: Devayani Khare

Over the three days, we cruised along the Sundarbans. Wildlife sightings were few, and far between – yet offered rare glimpses into the resilience of creatures in this adverse, brackish landscape. Ever so often, we encountered holidaymakers and casual tourists: there were more of them than the wildlife enthusiasts, reflecting what tourism development would mean for the Sundarbans. I believe everyone should have access to a destination, however sensitisation, awareness, and education is a crucial part of tourism, especially in landscapes as fragile as deltas. In this context, geoscience can lay the foundations to ensure biodiversity, people, livelihoods, and infrastructure are resilient to environmental change and natural hazards, and how tourism can be beneficial in the long-term.

Cited Literature:

[1] Dasgupta, Susmita, David Wheeler, Md. Istiak Sobhan, Sunando Bandyopadhyay, Ainun Nishat, and Tapas Paul. 2020. Coping with Climate Change in the Sundarbans: Lessons from Multidisciplinary Studies. International Development in Focus. Washington, DC: World Bank. doi:10.1596/978-1-4648-1587-4. License: Creative Commons Attribution CC BY 3.0 IGO

[2] Cracks in the shield: How the Sundarbans is dying and making Bengal prone to cyclones, News Laundry, Dec 2020

[3] Sunando Bandyopadhyay, Dipanwita Mukherjee, Sima Bag, Dilip Kumar Pal, Rabindra Kumar Das, and Kalyan Rudra. 2004. 20th Century Evolution of banks and islands of the Hugli estuary, West Bengal, India: evidences from maps, images and GPS survey. Geomorphology and Environment.
[4] McIvor, A.L., Spencer, T., Möller, I. and Spalding. M. (2012) Storm surge reduction by mangroves. Natural Coastal Protection Series: Report 2. Cambridge Coastal Research Unit Working Paper 41. Published by The Nature Conservancy and Wetlands International. 35 pages. ISSN 2050-7941. URL: http://www.naturalcoastalprotection.org/documents/storm-surge-reduction-by-mangroves


Adrift along the Sundarbans mangroves, east India by Devayani Khare is licensed under a Creative Commons Attribution-ShareAlike 4.0 International License.

Taking the measure of the measurer

Featured image: A USGS “Did you feel it?” map for a M6.5 earthquake that occurred in the Monte Cristo Range in Nevada on May 15th, 2020 (public domain)

Paper: Which earthquake accounts matter?
Authors: Susan E. Hough and Stacey S. Martin

Seismologists who study earthquakes spend much of their time looking at wiggly lines that represent recordings of ground motion from seismometers, but in places where those data aren’t available, we often turn to what we call “macroseismic” data: eyewitness accounts from people who felt the shaking. But when we ask people on the ground, “Did you feel it?,” who is answering?

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Etched in stone: tracing earthquakes through archaeological ruins

The Shore Temple at Mahabalipuram, Tamil Nadu, India

Feature image: Shore Temple at Mahabalipuram, Tamil Nadu, India by Nireekshit, CC BY-SA 3.0

Article: Archaeoseismological potential of the Indian subcontinent

Authors: Miklós Kázmér, Ashit Baran Roy and Siddharth Prizomwala

India’s ancient monuments whisper more than just stories of past empires and civilizations: they also tell tales of its geological past. Evidence of earthquakes is etched in stone, displacements and warps that can help us identify past seismic events.

India’s documentation of earthquakes is sketchy, pieced together from historical data, monographs, and British records. In 1898, the first seismograph was established in Pune, Maharashtra, but serious instrumental recording only began when the 1967 Koyna Dam earthquake struck.Such a short record is not enough to map out active seismic regions or understand recurring earthquakes, so some scientists are turning to archaeological evidence.

Archaeoseismology studies past earthquakes by analysing damage to archaeological sites. How much damage an earthquake does to a structure depends on how hard or soft the ground beneath is, and damage may be mitigated through preventative building techniques. Earthquakes can result in shifts and tilts in masonry or brickwork, displaced walls, warped floors, missing sections, and sometimes, a complete collapse of the structure. The Earthquake Archaeological Effects (EAE) scale helps categorise the intensity of past earthquakes based on observations of structural damage.

A recent paper by Kazmer et al., looks at earthquake damage to 3 late medieval UNESCO World Heritage sites: Mahabalipuram in Tamil Nadu (7th-8th CE), the Qutub Minar complex in Delhi (12th-19th CE), and Konark near Bhubaneshwar in Odisha state (13th CE). All three sites feature masonry buildings commonly seen in 7th and 12th centuries CE architecture across the Indian subcontinent. The seismic history of the subcontinent is understudied compared to the seismically active Himalayan terrain.

The tilt of masonry wall and floor at the Shore Temple in Mahabalipuram indicates liquefaction, a sudden loss of soil stability that can be caused by a seismic shock.. In the Qutub Minar complex, damage to the minar including masonry blocks at the top of Iltutmish’s tomb with gaps of about 5 cms  are attributed to an earthquake in 1803. At Konark, smaller temples around the Sun Temple display shifted blocks. Other temples are missing a shikhara or deul, the temple spire or tower, which might have been toppled by an earthquake.

Beyond categorising such damage, archaeoseismology can indicate the date or date interval, location, and intensity for both seismically active and less active regions. Comparisons with historical records can offer broader insights into the Indian subcontinent. The volcanic plateau that forms the Indian peninsula has long been considered a ‘stable’ region, yet all 3 sites in this study located on the ‘Indian shield’ indicate otherwise – the region has seen earthquake activity in the past. 

Over the years, monuments have undergone intensive restoration by various rulers, British colonial authorities and the Archaeological Survey of India to preserve them for future generations, but in the process, the evidence of past earthquakes has been erased. Kazmer and co-authors suggest that archaeoseismic studies are conducted before all large-scale restoration projects. That way, we can ensure both the historical and geological legacies are preserved for posterity.


Etched in stone: tracing earthquakes through archaeological ruins by Devayani Khare is licensed under a Creative Commons Attribution-ShareAlike 4.0 International License.

What lies beneath: tracing human migrations through stone tools, India

A map demonstrating possible migration routes of modern humans

Featured image: Katerina Douka, Michelle O’Reilly, Michael D. Petraglia – On the origin of modern humans: Asian perspectives; Science 08 Dec 2017: Vol. 358, Issue 6368, DOI: 10.1126/science.aai9067 [1], CC BY-SA 4.0 (Wikimedia Commons) with minor edits

Paper: Human occupation of northern India spans the Toba super-eruption ~74,000 years ago

Authors: Chris Clarkson, Clair Harris, Bo Li, Christina M. Neudorf, Richard G. Roberts, Christine Lane, Kasih Norman, Jagannath Pal, Sacha Jones, Ceri Shipton, Jinu Koshy, M.C. Gupta, D.P. Mishra, A.K. Dubey, Nicole Boivin & Michael Petraglia

Modern humans evolved around 200,000 years ago in Africa, and dispersed from there to other parts of the globe. The Out of Africa theory is a well-established model that explains the early dispersal of Homo sapiens or modern humans from Africa, into Asia and Oceania. Among the routes proposed is the Southern Route migration from East Africa to the Near East, across the Red Sea, and around Arabia and the Persian Plateau to India, and then finally with modern humans settling in Asia and Australasia. 

India’s geographic location is a key piece of this puzzle. Mitochondrial DNA of contemporary populations in India indicate that the country was an important stepping stone in the colonisation of Australasia. However, the timeline for the proposed Southern Route migration is still a matter of debate – could dating the arrival and settlement of modern humans in India provide some clues?

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Could corals help study the variability of past Indian monsoons?

Featured image: A coral colony from Maldives, Indian Ocean. Picture credit: Андрей Корман from Pixabay (Public domain)

Paper: Potential of reef building corals to study the past Indian monsoon rainfall variability

Author: Supriyo Chakraborty

Paleooceanographers have often used reef-building corals to study oceanic processes like the El Niño and Southern Oscillation, ocean circulation patterns, air–sea gas exchange, and the Indian Ocean dipole (a.k.a Indian Niño), among others. Yet how exactly do corals provide clues about the physical and chemical conditions of their environments? The answer lies in their skeletons. 

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Where the river flows: India’s catchment crisis

Dandeli river, Karnataka, India

Paper: Insights into riverscape dynamics with hydrological, ecological and social dimensions for water sustenance

Authors: T.V. Ramachandra, S. Vinay, S. Bharath, M.D.Subash Chandran, and Bharath H.Aithal

A catchment or watershed represents an intricate network of streams that coalesce into a river. In ecology, river networks are considered as ecosystems since they facilitate interactions between organisms and their environments. A healthy river ecosystem sustains the biodiversity of fringing forests and aquatic habitats, and enhances the landscape’s resilience to water resource development, droughts and climate change. Rivers provide water for domestic, agricultural and industrial use, and sustain native vegetation which in turn regulates the water cycle, and provides forest-based goods and services.

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Rivers of Memory: India

Paper: Evolution of modern river systems: an assessment of ‘landscape memory’ in Indian river systems

Authors: Vikrant Jain, Sonam, Ajit Singh, Rajiv Sinha, S. K. Tandon

“A river cuts through rock not because of its power, but because of its persistence.”

James N Watkins

In geomorphology, the persistence of rivers is etched into the very landscape – a memory of the forces that once shaped it, and continue to do so, slowly, and inexorably. Landscape memory, as Gary John Brierley once wrote, is the imprint of the past upon contemporary landscapes, which include geologic, climatic, and anthropogenic factors.

The rivers of the Indian subcontinent bear witness to forces that shaped them over millennia – and a recent publication in the Journal of International Geosciences traces the evolution of India’s river systems at different time scales.

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