A new study has reconstructed nearly 4,000 years of climate and vegetation history of Majuli Island in Assam, offering fresh insights into long-term climate variability, flood dynamics and ecological change in the world’s largest inhabited river island.
Majuli, located in the Brahmaputra river system, is culturally significant as a settlement of several tribes and a major centre of Neo-Vaishnavite culture. The island has also been severely affected by recurrent flooding, riverbank erosion, deforestation and land loss.
The study, carried out by scientists from the Birbal Sahni Institute of Palaeosciences (BSIP), Lucknow, an autonomous institute under the Department of Science and Technology, is the first comprehensive palaeoecological reconstruction of Majuli based on integrated modern and fossil pollen records.
Researchers collected a 150-cm-deep sediment core from Sakali Wetland on Majuli Island and analysed pollen and grain-size data to reconstruct past vegetation, river dynamics and flood intensity. The findings provide a detailed environmental record of the island during the Mid to Late Holocene period.
The study, led by DST-INSPIRE SRF Arya Pandey and BSIP Scientist-E Dr Swati Tripathi, was conducted in collaboration with researchers including Dr Sadhan Kumar Basumatary, Dr Salman Khan, Dr Hema Singh, Dr Biswajeet Thakur and Dr Anupam Sharma.
According to the researchers, the island experienced an early warm and humid phase between around 4040 and 2260 calibrated years before present, marked by dense forest cover. This period showed resilience even during the 4.2-kiloyear dry climatic event.
The record then shows phases of changing monsoon intensity and flood activity, including a relatively moist phase between 1100 and 500 calibrated years before present, corresponding to the Medieval Climatic Anomaly. The past 500 years indicate declining temperature and rainfall, in line with the Little Ice Age, along with greater human influence and more scattered vegetation.
The grain-size analysis also points to a shift from low-energy to high-energy fluvial conditions, suggesting increasing hydrodynamic instability over time. Researchers said this improves understanding of the interaction between climate, vegetation and river processes in river island ecosystems.
The study further highlights the role of the Brahmaputra and its tributary systems in shaping the depositional environment and ecological dynamics of Majuli. Scientists said the integration of pollen and grain-size analysis offers valuable clues on past flood intensity, sediment transport and erosion processes.
Published in the journal Review of Palaeobotany and Palynology, the study presents the first multi-proxy reconstruction of long-term climate-vegetation dynamics and river processes on Majuli Island.
Researchers said the findings could support biodiversity conservation, wetland restoration, river management and climate adaptation planning, particularly for communities affected by recurrent flooding and land loss in the Brahmaputra basin.
