Adapting to Sea Level Rise: A Law of the Sea Perspective

According to the United Nations Convention of 10 December 1982 on the Law of the Sea (UNCLOS), maritime zones can be divided mainly into six areas as follows. The internal waters are located on the landward side of the baselines and comprise the maritime waters adjacent to the land territory of the coastal State (article 8 § 1 UNCLOS); the territorial sea is adjacent to the internal waters, and it measures 12 nautical miles from the baseline (articles 2 § 1 and 3 UNCLOS); the contiguous zone measured 24 nautical miles from the baseline where coastal State has, notably, policing powers in relation to its customs, fiscal, sanitary and immigration laws, and regulations (article 33 UNCLOS); the exclusive economic zone is 200 nautical miles wide (article 57 UNCLOS) where coastal State has sovereign rights on this zone in respect to environmental protection, scientific research, exploration, and the use of natural resources (article 56 UNCLOS). The continental shelf is the prolongation of the coastal State’s land territory submerged for 200 miles from the baselines when the outer edge of the continental margin is less or up to 350 nautical miles (or 100 nautical miles from the 2500 m isobath) if it is wider (article 76 UNCLOS). However, since the coastal State’s right to outer limits of continental shelf relies not only on the 200 nautical miles rule but also on the “natural prolongation” criterion, it implies that the outer limits of the continental shelf must not always be measured from baselines. The coastal State has sovereign rights over this area in respect to the exploration and exploitation of natural resources (article 77 § 1 UNCLOS). Finally, the high seas are not subject to the State’s sovereignty and are located beyond the external limit of the EEZ (as a maximum of 200 miles from the baselines) (article 86 UNCLOS). The outer limit of all these zones are determined and delimited from baselines except for one of the situations where outer limits of continental shelf exceed 200 nautical miles.

UNCLOS establishes the legal framework of baselines. However, in some cases, it appears that a distinction between baselines serving for measuring the limits of the maritime zones and baseline serving for establishing maritime boundary can be drawn.

Legal consequences of the sea level rise are difficult to predict with precision. The change in the coast can be in many ways. However, potential examples and situations can be examined. The first situation to address is that when base points and baselines shift (retreat) landward, and the second is when base points and baselines situated on islands, rocks, and low-tide elevations disappear.

Referring to the above analysis of low water normal baselines of article 5 of UNCLOS, it is understood that there is a common uncertainty related to the coastal State having the choice regarding which one is the low-water line, which is inherently changing by sea level rise. It is to recall that the lower water line is the starting line of the outer limits of maritime zones.

In interpreting article 5 of UNCLOS, the International Law Association’ (ILA) Committee on Baselines under the International Law of the Sea has argued that the charted low-water line is the legal normal baseline and the chart itself is the legal document that determines the position of that baseline irrespective of the physical realities of the coast.⁴² As discussing above, the low-water line depends on the choice of vertical datum that is the level of reference for vertical measurements of a tide.

Article 5 of LOSC presents another uncertainty in that it does not specify a particular vertical datum and thus low-water line to be used. “With respect to the changes in the location of the low-water line caused by the tidal cycle, this line can be fixed by identifying the single vertical, or tidal, datum (among several used in the hydrographic community) to represent low tide. This vertical datum is the ‘zero level’ to which elevation and depth measurements are reduced. The intersection of the sea—when it is at that chosen level—with the coast is the low-water line. The low-water line thus defined is an elusive feature if not a purely conceptual construct.”⁴³ Therefore, the choice is left to the coastal State since there is no “wrong” answer.⁴⁴

Once the selected low-water line is shown on the charts officially, there is therefore recognition by coastal States and normal baseline could remain in place, irrespective of sea level rise. This would ensure safety and prevent navigation from uncertainty.

However, another interpretation was given to article 5 of UNCLOS by the ILA in the case of unstable coasts due to sea level rise. Normal baselines could adapt to physical realities, and therefore they could be dynamic.⁴⁵ This means that it would create a baseline system that reflects the actual geographical conditions by being ambulatory.⁴⁶

The ambulatory approach considers that the Convention does not provide any provision on the consequences of sea level rise on the baselines, islands, and low-tide elevations, and consequently nothing can require from a coastal State to permanently fix its limits and boundaries. The very few provisions that might be seen as dealing with stability of maritime limits are related to the continental shelf and with the deltas’ baseline provisions, but they are far from being sufficient. Thus, with regard to the continental shelf, UNCLOS requires from the coastal State to “deposit with the Secretary-General of the United Nations charts and relevant information, including geodetic data, permanently describing the outer limits of its continental shelf.”⁴⁷ As to the baselines of the deltas, UNCLOS provides that “the appropriate points may be selected along the furthest seaward extent of the low-water line and, notwithstanding subsequent regression of the low-water line, the straight baselines shall remain effective until changed by the coastal State in accordance with this Convention.”⁴⁸

The ambulatory or shifting baseline approach has been developed by some scholars⁴⁹ who consider that with sea level rise uncertainty in maritime boundaries is created in that the baseline from which the boundary is drawn is ambulatory. In this sense, when feature from or on which the baseline is drawn disappears, the baseline must move and the maritime boundary generated from it has to be redrawn and calculated from the new baseline. Therefore, the maritime boundary generated from the previous disappeared baseline is not valid anymore and is reestablished from the new baseline. In this case, the outer limits of maritime zones are ambulatory in that they will move with the baselines from which they are measured and normal baselines may change with the change of the low-water line.⁵⁰

The disappearance of baseline point implies the disappearance of the boundary generated by that point. The boundary though follows respectively the “movement” base point and the baseline. It results that maritime limits and boundaries shift when baselines shift, islands, or low-tide elevations disappear.

Some scholars have suggested that the implications of sea level rise on maritime boundaries could lead to “renegotiation of maritime boundary agreements based on the principle of equidistance to correspond with new geographic realities; re-evaluation of both equity and equidistance principles by international courts and tribunals in settling boundary disputes; or finally, reversion of highly disputed exclusive economic zone claims to the legal status of high seas.”⁵¹ This was, for example, the case of the two coastal State neighbors Switzerland and Italy.⁵² The maritime boundary between these States shifts because of the height of the glaciers. Therefore, it was not permanently determined and led the parties between 2008 and 2009 to negotiate the definition of a new maritime boundary.⁵³

This shift may generate some critical consequences. It would create uncertainty in maritime boundaries that would not be appreciated by a law that aims to generate stability between States in their relation. Modifying maritime boundaries regularly would create legal insecurity for States that have a constant unstable coast. They would have to constantly review their maritime limits and boundaries, and this would also create conflicts and instability for any neighboring state, even those that have more stable baselines.

In fact, the change of baseline could create conflicts between adjacent or opposite coastal States over the exploitation of natural resources.⁵⁴ If the shift of baseline is to be applied, some States that would lose part of their territory, islands, or low-tide elevations may invest huge financial efforts to maintain them even “artificially.”⁵⁵ On the other side, by adjusting and correcting baselines, coastal States must take into consideration the costs of adaptation and the time that has to be spent in the long process of modifying maritime borders. Moreover, by applying the ambulatory baseline approach and if baselines are not marked on large-scale charts, navigation charts would not be precise in determining the maritime limits and boundaries and ships would not know exactly in which zone they navigate and to which rights they are subject (right of innocent passage, fishing rights, etc.).

In State practice, some States having an unstable baseline have made reference, in their national legislation, to the point on which the base point is situated without indicating the exact geographical coordinates of the point. To avoid the risk of establishment of a baseline that would not be stable, some States did not register their geographical coordinates but are content in the publication of the marine charts, which are formally easier to update with more flexibility in determining base points. For example, the Mexican legislation, in determining base points in the Mexican Golf, indicated that the departure point of the baseline is situated in the middle of the point in the mouth of Rio Grande without adding any precision about the geographical coordinates about this point.⁵⁶

Taking into consideration all these implications of the shifting baseline approach, the ILA argued that the actual low-water line is the legal normal baseline and charts, and it should be considered as the evidence of the physical coastal realities or the actual coastal configuration.⁵⁷ The interpretation of article 5 of UNCLOS by the coastal State is fundamental for addressing the potential impacts of sea level rise with regard to maritime zones.

As discussed above, neither in the case of normal baselines nor in straight baselines does UNCLOS provide that the maritime zone limits and boundaries can move with baselines. It “permanently” fixes the outer limit of the continental shelf to every State since they have to deposit to the Secretary-General of the United Nations charts and relevant information, including geodetic data, permanently describing the outer limits of their continental shelf.⁵⁸ It also fixes the baselines for deltas and other natural conditions that make coastlines highly unstable. Since UNCLOS does not fix the outer boundary of the territorial sea, the contiguous zone, and the EEZ, one may think that these maritime zone boundaries can be ambulatory. However, the unique provision of UNCLOS to the question of instability of geography is illustrated in article 7(2).⁵⁹ It indicates that despite the possible shift of the coast landward, the appropriate points and the straight baselines joining them “shall remain effective until changed by the coastal State.” This article would present some help in our contest because it concerns, according to the Convention, the case of “the presence of a delta and other natural conditions the coastline is highly unstable (emphasis added)” (article 7 (2)). Although it is unclear in which case a coast can be considered as highly unstable, the ICJ in the Nicaragua/Honduras case, noting the highly unstable nature of the mouth of the River Coco at the Nicaragua-Honduras land boundary terminus, decided that fixing base points on either bank of the river and using them to construct a provisional equidistance line would be “unduly problematic.”⁶⁰

However, the Convention is silent about the legal solution for changes of coasts or disappearance of features on which baselines and base points are established. The preservation of baselines and base points approach have been proposed in 1990 by A.H.A. Soons and was followed by several scholars:⁶¹ “[C]oastal states are entitled, in the case of landward shifting of the baseline as a result of sea level rise, to maintain the outer limits of the territorial sea and of the [exclusive economic zone] where they were located at a certain moment in accordance with the general rules in force at that time.”⁶² Following this idea, other scholars (Prescott and Schofield) have underlined that some States, such as the United Kingdom and the Netherlands, have considered the nautical chart as the only legal document that defines baselines. In fact, by recognizing that coastline change by the time, the nautical chart or the straight baseline geographical coordinates as deposited in the Secretary-General must remain the reference legal document regardless of the coastline changes.

By fixing permanently the baselines, resource conflicts between States are avoided. It could appear that the coastal State that had less than 200 nautical mile EEZ and has lost part of its coast would gain more maritime resources because its coastline retreats, but all States would not have more than they are entitled to under the Convention. It is important to understand that since the breath of the maritime zones is fixed by UNCLOS, equity considerations impose States to recall that choosing to fix the boundaries or to adjust them with the ambulatory baselines and base points will not allow States to gain more than what they presently possess.⁶³

Changing boundaries to adapt to the coastline changes would lead the state to protect the baselines by artificial costly installations. However, fixing baselines would avoid costs of adjustment to constant uncertain changes of the baselines⁶⁴ and costs of nautical maps modifications.⁶⁵

By fixing the boundaries, the principles governing the oceans and those agreed upon related to the maritime zones and maritime boundaries by the States to the Convention in their negotiations are preserved. Fixing (freezing) baselines would promote stability in the location of limits of maritime zones and also in maritime delimitation boundaries—bilateral and multilateral—agreements. And as the ICJ stated in the Temple of Preah Vihear case, “when two countries establish a frontier between them, one of the primary objects is to achieve stability and finality.”⁶⁶ The Division of Ocean Affairs’ Handbook on Maritime Delimitation underlines that maritime boundary delimitation agreements “have a vocation for permanence and stability.”⁶⁷

Baselines, because they have legal meaning and not only a geographical meaning, are characterized by legal stability and should not be moving with the geography. The law of the sea in general is the law that governs relations between States in their maritime affairs.⁶⁸ In this sense, what fundamentally interests the law of the sea, including the Convention, is the stability and security of the relations between States, including in their international boundary regime. Even though the particularity of this law is that it is based on geography—in which change and instability are inherent—law is considered the priority because it provides stability and security and answers perfectly to the objectives of the Convention. Thus, in stating factors that States should consider in boundary negotiations, the UN Division for Ocean Affairs and the Law of the Sea advises States not to take into consideration any future geographical or geological shifts and the corresponding impacts on resource distribution or equities.⁶⁹

Moreover, the Law of the Sea Convention is not the sole source of law governing maritime affairs and entitlements. Reference is made to other complementary Conventions that regulate general international law aspects in the law of the sea such as boundary agreements. According to the Vienna Convention for the Law of Treaties,⁷⁰ stability of boundary agreements is achieved regardless of coastline movement. Even though geography changes and baseline shifts, maritime boundary agreements and their geographical coordinates remain secure and stable.⁷¹

Article 62 of the Vienna Convention, however, underlines an exception by which a State can unilaterally terminate an agreement because of a fundamental change in circumstances (rebus sic stantibus ⁷² or “things standing thus”). In the light of this article, some scholars have considered that a change in the geography would be a fundamental change that justifies the termination of an agreement and therefore its revision or replacement by a new agreement that would take into consideration the new situation. The question that can arise here is as follows: is an involuntary change of circumstances based on geography considered a fundamental change? Can one of the parties invoke article 62 to unilaterally terminate the maritime boundary agreement? The answer must be preceded by a clarification. Both parties know, at the time of conclusion of their maritime boundary agreement, that change of geography is inherent to this kind of agreements and can initially be expected; thus, stable geography is not the “circumstance” that forms the ground of their consent. Therefore, article 62 of the Vienna Convention cannot be invoked, and coastline changes will not affect the maritime boundary agreement. International Courts have not accepted the recognition of the right of unilateral termination, given the importance of the stability of the treaty regime.⁷³ Some States like Argentina and Chile have expressly rejected the application of this theory.⁷⁴ Moreover, the terms of article 62(2) of the Vienna Convention explicitly excludes boundary agreements; although it is still debatable by the doctrine if it also applies to maritime boundaries, it stipulated that “[a] fundamental change of circumstances may not be invoked as a ground for terminating or withdrawing from a treaty […] if the treaty establishes a boundary […].”⁷⁵ The ICJ in the Aegean Sea case implied that maritime boundaries fall within the Article 62(2) exception: “Whether it is a land frontier or a boundary line in the continental shelf that is in question, the process is essentially the same, and inevitably involves the same element of stability and permanence, and is subject to the rule excluding boundary agreements from fundamental change of circumstances.”⁷⁶ A state would therefore be unlikely to succeed in unilaterally terminating a maritime boundary treaty by invoking the principle of rebus sic stantibus under article 62 of the Vienna Convention.⁷⁷

However, the stability of boundaries and the legal stability are defended by the legal reasoning⁷⁸ even though the approach of fixing baselines is criticized by being inappropriate and insufficient.⁷⁹ Avoiding instability and insecurity in maritime limits and boundaries would lead to fix them as they are situated at the time of agreement between States and at the time of deposit to the UN Secretary-General. Article 76 paragraph 9 of UNCLOS can be applied analogically to fix baselines and boundaries even though the technic of fixing them is not established yet.