The impact of sea level rise on the stability of maritime boundaries under international law

Abstract

Sea-level rise presents a significant challenge to the legal framework governing maritime zones under international law. The United Nations Convention on the Law of the Sea establishes that maritime zones are measured from baselines determined by the coastal State’s shoreline. However, rising sea levels threaten the stability of these baselines by altering coastal geography, potentially leading to the contraction of maritime zones and thereby possibly creating uncertainty in the stability of maritime boundaries. This dissertation examines the extent to which existing international law accommodates the impacts of sea-level rise on the stability of maritime boundaries. The study analyses the legal regime governing baselines under the UNCLOS and evaluates how these rules interact with dynamic coastal changes. Particular attention is given to provisions within the Convention that promote stability. The research also considers the broader principles of legal certainty and stability in maritime delimitation, as reflected in international jurisprudence and state practice. Furthermore, the dissertation explores emerging approaches proposed by scholars and leading international organisations to address the legal uncertainties caused by sea-level rise, including the concept of fixed or ambulatory baselines and the possibility of maintaining established maritime boundaries despite geographical changes. Developments within international law, including discussions within the International Law Commission and state practice supporting the permanence of maritime zones, are also examined. The analysis demonstrates that while UNCLOS does not explicitly address sea-level rise, its underlying principles and certain provisions support the stability of maritime boundaries. The dissertation concludes that maintaining established baselines, drawn according to international law, despite coastal changes offers the most legally coherent and equitable approach, particularly for vulnerable coastal and less developed States facing the existential consequences of climate change.