Fluctuating boundaries in a changing marine environment

Environmental changes, such as sea level rise and coastal erosion, have an increasing impact on coastlines worldwide. Unilaterally declared maritime limits are generally determined by reference to coastlines and they are only binding insofar as they conform to the applicable law. Bilateral maritime boundaries are not equally affected by changing coastal geography because, once established, they are binding on parties to the arrangement under the pacta sunt servanda and res judicata principles. Maritime delimitation generally produces geographically stable boundaries. In principle, these remain fixed notwithstanding changes to the coastal geography that generates maritime entitlements or the ecosystems central to national interests. Indeed, stability and predictability are among the objectives of maritime delimitation. However, legal stability can be achieved without geographic stability and the requirement of predictability may be unattainable in a new world of environmental uncertainty. After all, baselines and derived outer limits fluctuate to reflect changing coastal geography and the same is true of bilateral boundaries, unless and until otherwise agreed. States have concluded boundary agreements that refer to fluctuating concepts, such as the equidistance line, instead of fixed co-ordinates. Furthermore, the International Court of Justice has left a segment of a maritime boundary to fluctuate until otherwise agreed and a Chamber of the Court has addressed the possibility of establishing a boundary by reference to a fluid oceano-biological boundary in the marine environment. This suggests that maritime boundaries can fluctuate if established by reference to sufficiently clear and relevant limits in the natural environment.