Just like many other people, I was overwhelmed when the massive earthquake struck Japan on March 11, 2011. While reading news about how resilient Japan had been in facing the disaster, a friend of mine sent me a news link. It was about how the quake had displaced Japan by more than 2 meters.
“What was its impact on borders between countries?” my friend asked. The question was apparently about borders at sea (maritime boundaries), since Japan does not share land territory with other countries. He might have imagined the case of international borders like a fence sitting between two houses. When one house shifts relative to another, should the fence also be moved?
My friend’s question really made me think. Whether maritime boundaries can change due to the change of a coastline as a consequence of a natural disaster is a valid question. From a broader perspective, when coastlines change, for whatever reason, will the limits of a state’s maritime entitlement also change? Let us take a closer look.
The first key issue to address is: What is the basis for claims to offshore areas? In fact it has been well established as a principle of international law that “the land dominates the sea”. That is, claims to maritime jurisdiction over areas of the ocean arise on the basis of sovereignty over land territory. Thus, according to the United Nations Convention on the Law of the Sea, a coastal state like Japan or Indonesia is entitled to maritime areas or zones of maritime jurisdiction, the breadth of which are measured from its baselines. In most cases, baselines are, in fact, coastlines during low tide.
Measured from these baselines, a coastal state can have territorial sea out to 12 nautical miles (nm), a contiguous zone out to 24 nm, exclusive economic zones (EEZ) out to 200 nm and a continental shelf out to up to 350 nm or more from baselines. Analogous to a home, the maritime entitlement is like a house having front, back, and side yard around it.
Imagine there is a state in the middle of the ocean with no neighbors nearby. The state is allowed to define the limits of its maritime area pursuant to the Law of the Sea Convention without a need to deal with other countries. This is called a unilateral process. However, in reality, every state around the world has at least one neighbor. That is, every coastal state’s maritime claims overlap with another neighboring state or states giving rise to many maritime boundaries to be settled, worldwide.
Like at home, front fences can be built unilaterally but side fences must be settled with neighbors. For the case of a state, a unilateral border is usually called the “maritime limits” and a bilateral one with a neighboring state is known as a “maritime boundary”.
Baselines play an important role in defining maritime limits because baselines are the reference from which maritime limits are measured. Similarly, baselines are also vital in constructing maritime boundaries between states. When baselines shift, will maritime limits or maritime boundaries also move? Yes, maritime limits can shift if baselines move.
The shift of a coastline due to, for example, land displacement as a consequence of an earthquake, sea level rise, or erosion requires coastal states to redefine their baselines. This involves surveys and mapping, particularly hydrographic surveys. In many cases, coastlines shift landward so that baselines also move landward and consequently land territory shrinks.
Since maritime limits are measured from baselines, they too will move landward. In this case, the total area of land territory and maritime area decreases. They shrink.
How about if the whole area of an island is displaced, like what happened to Japan’s Honshu Island? In this case, the shape and size of the island might not change but its coastlines/baselines have certainly shifted. Consequently, maritime limits will also move relative to the “new” location of its baselines. This requires a technical investigation, which includes accurate surveys and mapping to identify the spatial extent of the shift.
While maritime limits can shift due to changes to coastline/baselines, this is not the case for maritime boundaries. Once agreed by two or more states, maritime boundaries stay where they are. Maritime boundaries do not change unless the parties in question agree that the boundary in question should change.
Indeed, boundaries and boundary treaties have a privileged place in international law. The 1969 Vienna Convention on the Law of Treaties (Article 62 (2) (a)) states that boundary treaties are excluded from the rule that a party to a treaty may invoke “a fundamental change in circumstances” as grounds for terminating a treaty.
In addition, the 1978 Vienna Convention on Succession of states in Respect of Treaties (Article 11 (a)) also provides that a change of states does not affect a boundary established by a treaty. In other words, agreed maritime boundaries are fixed in terms of location even if baselines from which they are constructed have shifted.
To answer my friend’s question, the displacement of land territory and the change of coastline will not alter agreed maritime boundaries established bilaterally between neighboring states. However, it can change a coastal state’s unilaterally-defined maritime limits. If we think of a home, once again, the front fence that is defined unilaterally may shift due to the shift of the house but not the side fence that has previously been agreed to with neighbors.
Will the size of Japan’s maritime area change due to potential shift of its maritime limits? It all remains to be seen. Thinking of maritime limits and boundaries does not seem to be the first priority for Japan at the moment.
Nonetheless, it is good to be aware that the time to deal with it will certainly come not in the very far future. This is not only applicable to Japan but also to other coastal states in the face of their coastal instability due to natural disasters, sea level rise, or land subsidence.
The writer is a lecturer at the School of Geodetic Engineering, Gadjah Mada University. His research interest is in the technical/geodetic and legal aspects of maritime boundary delimitation. This is his personal opinion.
