Atoll Habitability

PhD Student - Mayukh Dey

Program - Oceans and Coasts Program

Guide - Rohan Arthur

The project addresses issues of immediate relevance to the continued survival of island societies living in Lakshadweep. Despite being the smallest UT in India, its dense human population of 65,000+ individuals are completely dependent on the continued protection atolls afford them. This study will provide realistic and differentiated projections of climate change impacts on the future habitability of their islands over the coming decades. Seen through the lens of reef decline, island stability and freshwater, it addresses critical pillars of habitability that will need to urgently be addressed to prevent Lakshadweep islanders from becoming one of India’s first climate refugees. Beyond this, my project will contribute to a larger understanding of i) the anthropogenic and environmental factors that determine freshwater budgets on low-lying islands; ii) the long-term dynamics of reef accretion, and the influence of climate change disturbances on rates of reef growth; and iii) compromised ecological functioning of coral reefs and interactions with oceanographic factors in determining atoll behaviour; and iv) highlighting the importance of human agency and their ability to influence a region's environmental vulnerability. This will contribute a nuanced understanding of not only the geophysical limits to habitability, but also help highlight how many vulnerabilities in our projected climate scenarios can also be altered. This study adds to a global debate that is largely focused on establishing two contrasting viewpoints of an atoll’s ability to cope or sink with climate change, while filling a much-needed data gap in the northern Indian Ocean.

Atolls around the world are characterised by small habitable land areas, low elevation gradients and relatively bounded socio-ecological systems. Human survival on these islands primarily depends on the integrity of coral reefs, the stability of the land, and the availability of freshwater. These form the primary pillars of atoll habitability, and are all linked - directly or indirectly - to the various regulatory and provisioning functions that the coral reef provides. The buffering capacity of coral reefs and their ability to generate sediments is what creates the conditions necessary for land to form within the calm lagoons of atolls. Sediments generated from the reef are transported by wind and waves over thousands of years and form the basis for island formation, together with native vegetation, guano from nesting birds, and other soil formation processes. Rainfall then infiltrates as freshwater beneath the island, which floats as a thin lens on top of more saline water. The calm lagoons, stable land and finite but sufficient freshwater together ensured that human societies were able to sustain themselves on atolls. However, given the pace of climate change, there is growing concern that the integrity of all three pillars of habitability is being compromised, threatening the economy, livelihoods and survival of thousands of people who live on atoll islands.

In this doctoral study, I will attempt to disentangle the complex interaction between the reef, land, and freshwater in the Lakshadweep archipelago by adapting an inter-disciplinary approach and combining ecology, geomorphology, oceanography and hydrology. The Lakshadweep archipelago is home to approximately 65,000 people and the need to investigate their islands’ vulnerability has never been so pressing. My study will be concentrated on the three atolls of Kavaratti, Agatti and Kadmat which follow a strong gradient of human density. First, I will attempt to gauge the state of coral reefs in Lakshadweep that have been marred by three mass bleaching events in the past quarter of a century. Examining the altered community composition will help me understand the two most important ecosystem functions of coral reefs – wave buffering and sediment generation capacity. Thus, for my second chapter, I will attempt to quantify these critical functions for our selected atolls, focusing on sediment production and distribution. In the third chapter, I will characterise the climatology of the Lakshadweep and determine its current vulnerability given its location. Further, I will assess the risk of island inundation and freshwater contamination, and identify regions that are the most susceptible, based on the elevation profile of the islands, and wave buffering abilities of the reef. For my fourth chapter, I will attempt to estimate a water budget for the atolls while factoring in rainfall patterns, human extraction and plant transpiration rates, and how these components interact with the finite potable groundwater lens in selected atolls. Finally, I will attempt to discuss the potential future of the Lakshadweep and how physical risks interact with human agency to further aggravate or diminish vulnerability to climate change. This nuanced approach, I believe, is critical for directing our finite resources when climate change mitigation strategies are devised for the islands.

Mayukh Dey, Wenzel Pinto, Radika Nair, Rajeswari BT, Sidharth Sankaran, Siddhi Jaishankar, Dr. Jagdish Krishnaswamy, Dr. Chris Perry, and Dr. Rohan Arthur

Mayukh is an ecologist by the day and a bassist by night. When not in the islands he plays for a jazz fusion trio - Preacher and her Creature Feature.

Listen to his latest album, 'Some Minor Feet' on:

Spotify - https://open.spotify.com/album/79lPsnpgJHJDYwFiggCMWe?si=XNDEERksRxu0QO_OUxcIFQ

YouTube - https://www.youtube.com/channel/UC60RTFRnHlDV_kJvCCXJPuQ