Sea Level Rise and Its Implications in International Law

Sea Level Rise and Its Implications in International Law

[Tanishk Goyal & Dhruv Gupta are students at The West Bengal National University of Juridical Sciences, Kolkata.]


Of the multiple threats that climate change poses to the word order we live in, the rise in global sea level remains its most significant manifestation. While the rise in sea level has become a growing concern for States all over the world, its implications concern some States more than others. It is unarguable that Small Island Developing States (‘SIDS’) stand on the frontline and are the most vulnerable to the impacts of the rise in Sea level which directly threatens their very existence. For SIDS, the impacts of a rise in sea-level range from an impending threat of the displacement of their people to undermining their food and water security in the foreseeable future. However, for the purposes of the present piece, we limit our analysis to the implications of the rise in sea level on the delimitation of Maritime Boundaries, with specific emphasis on the fate of the Territorial Sovereignty and existing Maritime entitlements of SIDS under the United Nations Convention on Law of the Seas (‘UNCLOS’). However, before moving on to analyse the specific implications of the rise in sea level on SIDS and suggesting a way forward, it is necessary to address the inevitable clash which will occur between an emerging custom and the UNCLOS with a rise in sea level.

In order to do so, we begin in Part II discussing how the development of a subsequent custom due to emerging State Practice on the ambulatory baseline approach may be able to modify the UNCLOS. In Part III, we discuss how such a modification, (assuming that a subsequent custom on ambulatory baselines actually develops), being against equity would disproportionately impact the territorial sovereignty and extent of maritime entitlements of the SIDS. Finally, in Part IV, we conclude by emphasising how the fixing of Maritime entitlements by States should be the ultimate way forward especially against the backdrop of the equity and stability concerns which form the core principles of the UNCLOS and Public International Law.

Development of Subsequent Custom modifying Treaties under International Law.

The rise in global sea level has also rekindled the debate between fixed and ambulatory baselines under International Law. At the outset, Article 4 of the UNCLOS defines a Normal Baseline as the low-water line along the coast as marked on large-scale charts officially recognized by the coastal State. The normal baseline of a State is essentially used to calculate its Maritime Boundary and consequently, the extent of its Maritime entitlements under International Law. While an ambulatory baseline approach requires the limits of the Maritime Jurisdiction of States to correspondingly shift with a change in their normal baselines due to a rise in sea level; a fixed baseline approach requires States to permanently delineate the outer limits of their Maritime Jurisdictions by fixing their baselines which are to remain effective irrespective of the submersion of coastal areas due to the rising sea level.

Since the text of the UNCLOS does not explicitly provide that the maritime boundaries shall shift with a change in baselines, it can be said that the UNCLOS does not decidedly exclude the possibility of States resorting to either of the two approaches. This gives rise to the concerns as to whether the development of a subsequent custom on either of the two approaches may be able to modify the UNCLOS or not.

Ideally, a treaty can be modified by mutual  consent or the subsequent practice of all the States who are parties to it. One may then argue that the UNCLOS may be modified in a similar manner to accommodate the interests of the States with a rise in sea level. However, the traditional modes of modification by mutual consent and even subsequent practice may not be able to modify the UNCLOS. This is essentially because the modes of mutual consent and subsequent practice require the practice of all states in order to modify a treaty. In case of the UNCLOS the subsequent practice of all the States which are parties to the treaty will not be the same with respect to the determination of ambulatory and fixed baselines. While the State practice of developed States generally supports an ambulatory baseline approach, the State Practice of SIDS prefers a fixed baseline approach. The reason for this contradiction is the fact that a rise in sea level and a subsequent loss in the Exclusive Economic Zone (‘EEZ’) of developed states does not substantially curtail their freedom of navigation and entitlement in the high seas since their resources permit them to do so. Following an ambulatory baseline approach, while a rise in sea-level may reduce the EEZs of Developed States, they still stand to gain access to the maritime entitlements which were formerly under the EEZ of other States and now form a part of the High Seas. On the other hand, due to the scarcity of resources, the loss of an EEZ for SIDS would essentially curtail their control over their maritime entitlements and the economic resources off their coast, thus threatening their very existence under International Law. Thus, since the developed states stand to effectively benefit from contraction of maritime territories of SIDS and other coastal States, the subsequent practice of all the States with respect to the determination of ambulatory or fixed baselines cannot be the same.  

In such a scenario, there may be a possibility that the subsequent development of a rule of Customary International Law may be able to modify the Treaty, with respect to the approach preferred in delimiting maritime boundaries. Subsequent custom, unlike subsequent practice, does not require consent of all states, but only the relevant ones. However, there is lack of consensus between scholars on this contention. There have been arguments that treaties like UNCLOS and other bilateral treaties, which determine the boundaries between States should not be altered without adherence to set procedures. The same has gathered support from the Vienna Convention on the Law of Treaties (‘VCLT’) which has a special provision that protects boundary treaties from being terminated even in extreme situations such as those of ‘fundamental change in circumstances’. However, in our opinion, a subsequent custom has the power to modify the obligations under treaties without a formal change. While this is admittedly a heavy burden to discharge, certain historical delimitation treaties have actually been modified in such a manner (Convention for the Construction of a Ship Canal to Correct the Waters of the Atlantic and Pacific Oceans, arts. II-III, Pan-U.S. Nov. 18, 1903, 33 Stat. 2234;  Convention sur la peche maritime entre le royaume du Maroc et I’Espagne, Morocco-Spain, Art. 3,1969, reprinted in National Legislation And Treaties Relating To The Law Of The Sea 512, 513, U.N. Doc. ST/LEG/SER.B/16 (U.N. Legislative Series 1974); Convention Regarding the Abolition of the Capitulations in Egypt, May 8, 1937, reprinted in actes de la conftrence des capitulations: montreux, 12 avril-8 mai 1937, at 259 (1937); Act of Rabat on the Spanish-Moroccan Negotiations Concerning Maritime Fisheries, Morocco-Spain, May 12, 1973, reprinted in 5 new directions in the law of the sea 18 (Robin Chrchill et al eds. 1977); Espagneet Maroc: SignaturedeI’accorddepche du 18 aofdt 1983, 88 revue generale de droit international public 231-32 (1984); Kontou, supra note 10, at pp 69-70, 76).  At the outset, there exist atleast two instances which can be regarded as evidence of a subsequent custom modifying Treaty Obligations under International Law.

Firstly, It is pertinent to note that the treaty preceding UNCLOS did not provide for EEZs but regarded everything apart from territorial seas as high seas. When the drafting of UNCLOS began, a new custom was developing, granting every state an EEZ up to 200 nautical miles from their baselines. While this custom was subsequently incorporated in UNCLOS, States had begun to practice it long before UNCLOS came into force. It is interesting to note that, although such kind of State Practice violated the provisions of The Convention on the High seas which was in force at that time, and was resisted by the developed states Developed States and the ILC until the 1970s,[1] the EEZ eventually came to be accepted by States in light of the new customary norm. This has been viewed by various scholars to be evidence of a subsequent custom modifying the obligations under existing treaties.

Secondly, there has also been a demonstrated history of interpretingTreaties in light of the subsequent development of CIL. This approach finds mention in the case of Legal Consequences for States of the Continued Presence of South Africa in Namibia where it was said that [Treaty] interpretation cannot remain unaffected by the subsequent development of law.” Similarly, in Case Concerning Gabdikovo-Nagymaros Project,the ICJ noted that a  newly developed norms of environmental law are relevant for the implementation of the Treaty. While the debate regarding interpretation of a Treaty in light of the development of a subsequent custom, qualifying as its modification has been a long-running one, there is scholarly consensus on the fact that a sufficiently flexible treaty with multiple reasonable goals and purposes can accommodate an interpretation in light of the development of a subsequent custom as its modification under International Law.

In light of both of these factors, UNCLOS can arguably be modified by the subsequent development of a custom on ambulatory baselines. This is even more so,  because developed States, having the State Practice of an ambulatory baseline approach, may easily assert that their conduct is in line with the Treaty’s objects and purposes, perhaps because one of its ultimate goals is the efficient utilization of a State’s resources, making any interpretation that promotes such efficiency a fair reading. (This is not to say that the custom on a fixed baseline approach cannot be developed. This is just to establish, how an ambulatory baseline custom is more likely to develop, in light of the State Practice of Developed States, and how such a custom would subsequently reinforce the existing hegemony of Developed States over SIDS under International Law.)

The Disproportionate impact on the Territorial sovereignity and The Maritime Entitlements of SIDS

Assuming that an ambulatory baseline approach develops into a subsequent custom, thereby modifying The UNCLOS, a rise in sea-level would then have the following impact(s) on the SIDS.

Firstly, a rise in sea level would disproportionately impact the Territorial Sovereignty of SIDS. The essence of the concept of Territorial Sovereignty lies in the notion of title. The ‘title’ to a territory encompasses both the evidence which may help establish the existence of a right, and the actual source of that right. The principle of territorial sovereignty implies that a State exercises full and exclusive authority over its territory which cannot be interfered with by other States.

The UNCLOS gives every State the right to claim territorial sovereignty over its territorial sea up to 12 nautical miles from its baseline. The baseline considered for this purpose is the normal baseline. With a rise in sea level, these baselines are bound to move inwards and by way of necessary implication, the outer limit of the territorial sea, the EEZs and the contiguous zones would also move inwards. This would subsequently result in the contraction of the area over which States can claim its title or other limited rights, thus, essentially resulting in their loss of Territorial Sovereignty over certain maritime areas. While this direct loss of territory can arguably be tackled by Developed States, which have the resources to undertake large-scale coastal fortifications in order to physically protect their territories, such an option is not feasible for SIDS. Thus, the inability of SIDS to physically protect their Territorial Sovereignty due to the dearth of resources, makes them more susceptible to the rise in sea level than Developed States.

Secondly, the GDP of SIDS is highly dependent on the extent of  their maritime entitlements, such as oil and gas deposits, fisheries etc which would be directly affected with the loss of their Territorial Sovereignty. In such a scenario, with a rise in sea-level, an ambulatory baseline approach would shift the marine entitlements of the SIDS formerly under the jurisdiction of their respective EEZs to the High Seas where they will have to compete with the developed States in exploring and exploiting portions of their own maritime entitlements. Owing to their limited resources, and fragile economies this will prove to unviable and incredibly expensive for SIDS. Moreover, the inability of SIDS to cope with an ambulatory baseline approach would also be aggravated by their unwillingness to be involved in expensive litigation with the developed States over the control of their marine entitlements which subsequently form a part of the high seas.

The use of an ambulatory baseline approach for the delimitation of maritime boundaries under International Law, therefore essentially leads to a situation where a rise in sea level would have no practical effect on the territory and extent of marine entitlements of Developed States. On the other hand, such a rise in sea level would either reduce the territory and marine entitlements of SIDS or make them the subject matter of Inter-State disputes. Illustratively, SIDS stand to lose control over portions of their most valuable marine entitlements while having contributed to less than 1 percent of the Global Green House Gas (‘GHG’) emissions. On the other hand, the developed States, having contributed the most to the global threat of climate change, stand to gain the benefits from the same natural resources as they shift from the EEZ of the SIDS to the High Seas.

This disproportionate impact on SIDS is antithetical to the principles of equity and fairness under the General Principles of International Law. This has been amply illustrated by International Courts and Tribunals which have time and again, applied the elements of equity and fairness in determining boundary lines over maritime areas while taking into account the impact on the geography and maritime entitlements of States, their ability to engage in coastal reinforcement to protect their marine entitlements and their contribution to climate change.

Apropos the foregoing discussion, it can be said that while the development of subsequent custom, may modify UNCLOS to disproportionality affect SIDS, the principles of equity and fairness may possess the potential to weigh-in the competing claims of Developed States and SIDS and suggest the ultimate way forward.

Fixing Baselines to delimit maritime boundaries: The way Forward

Until recently, the State Practice of Developed States supported an ambulatory baseline approach to delimit maritime boundaries under International Law. However, a fixed baseline approach is now being adopted by States in the Pacific Region for the same purposes.

This is essentially against the backdrop of the  principles of stability, certainty, equity and fairness which form the core principles of the UNCLOS. These principles mandate the fixing the baselines and delineating the outer limits of the maritime zones by States in order to permanently establish their maritime entitlements in accordance with the UNCLOS. The fixing of such baselines permanently without taking into account the sea level rise ensures that SIDS and Developed States continue to benefit from the marine entitlements within their respective EEZs despite any physical changes to a State’s geography with a rise in sea level.

Having said that, it is also pertinent to note that even a custom of fixing of maritime boundaries has both advantages and disadvantages. The major advantage as discussed in this paper includes the states being able to retain sovereignty over their current territories without having to forego any part of the territory in the case of a rise in sea level. However, the major disadvantage would be that the same would prima facie be violative of UNCLOS. 

However, in any case, this situation presents yet another opportunity to answer the highly debated hierarchy between custom and treaty. Moreover, with the majority of states’ interests tied with this, there is a pressing need in the international community to come up with a definitive answer conclusively. This situation also represents yet another ever-lasting concern of the third world’s practical equality in international law. The rise in sea level therefore poses a large concern for not only matters under environment law but various other fields of study. Whereas multiple steps are being taken to reduce the rise in sea level, it seems that the development in public international law is not expeditious as the International Law Commission took up this matter as recently as 2019 while the same has been a grave concern for the International Community for the last two decades.

In addition to the reviewers of the Opinio Juris blog, they would also like to thank Mahima Cholera and Adrija Ghosh for their invaluable inputs on the previous drafts of this piece.

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