Climate Change Impacts on Coastal Agriculture in Tamil Nadu, India: An Assessment of Sea-Level Rise and Salinity Intrusion

Background: The coastal districts of Tamil Nadu, spanning approximately 1,076 km of the Bay of Bengal shoreline, are among the most agriculturally productive and climatically vulnerable regions in peninsular India. Accelerating sea-level rise and progressive salinity intrusion now pose existential threats to coastal farming systems, with cascading consequences for food security, rural livelihoods, and ecosystem services. Objectives: This systematic review synthesises peer-reviewed literature published between 2017 and 2026 to assess the nature, magnitude, and spatial distribution of climate change impacts—specifically sea-level rise (SLR) and salinity intrusion—on agriculture in coastal Tamil Nadu. It further evaluates the current state of adaptation science and identifies critical knowledge gaps. Methods: Following PRISMA 2020 guidelines, a structured search of six databases (Web of Science, Scopus, Google Scholar, ScienceDirect, PubMed, and CGIAR/ICAR repositories) yielded 2,847 initial records. After systematic screening, 66 studies met full eligibility criteria, of which 47 were included in quantitative synthesis and 28 in meta-analysis. Results: Satellite altimetry data indicate a mean sea-level rise rate of 3.4–4.1 mm per year along the Tamil Nadu coast since 1993, with ensemble projections estimating 0.4–0.8 m of rise by 2100 under RCP 4.5–8.5 scenarios. Salinity intrusion currently extends 15–40 km inland along major estuaries during the dry season, with electrical conductivity values in affected paddy soils frequently exceeding 8 dS/m—well above the critical threshold for rice (Oryza sativa L.) cultivation. Yield losses in affected areas range from 25% to 70% for rice, 20–55% for groundnut, and up to 80% for banana in severely impacted zones. Districts of Nagapattinam, Tiruvarur, and Ramanathapuram are identified as hotspots of compounded vulnerability. Conclusions: The convergence of SLR, increased cyclone intensity, and salinisation represents a systemic risk to coastal agricultural sustainability in Tamil Nadu. Evidence-based adaptation strategies, including salt-tolerant variety deployment, managed aquifer recharge, and integrated coastal zone management, are urgently required. Significant research gaps persist in socioeconomic impact quantification and long-term monitoring. This review provides a consolidated evidence base for policymakers, agronomists, and climate scientists.