How Are National Borders Drawn? Rivers, Rulers and Old Treaties
By the BrainSnail editorial team. How these articles are written and checked, and how to tell us when one is wrong.
Look at a map of Africa and about a third of the boundaries are straight lines, which no natural feature ever produces. Look at Europe and almost none are. The difference is not geography but history: lines drawn by people who had been to the place tend to follow rivers, ridges and the edges of who lives where, and lines drawn by people who had not tend to follow latitude. Both kinds are still in force, and the ones drawn badly are still generating conflicts a century later.
The kinds of line
Political geographers sort boundaries by what determined them, and the categories predict how much trouble each causes:
- •Physical boundaries follow a natural feature, usually a river, a watershed or a mountain ridge, which is convenient and creates its own problems when the feature moves
- •Ethnographic or cultural boundaries follow the distribution of a language or people, which minimises grievance and is impossible to draw cleanly anywhere populations are mixed
- •Geometric boundaries follow lines of latitude and longitude, quick to specify and indifferent to everything on the ground
- •Antecedent boundaries were drawn before an area was substantially settled, so the population grew around them, as much of the American and Canadian west was
- •Subsequent boundaries were drawn after settlement and had to accommodate what was already there
- •Superimposed boundaries were forced on an existing population from outside, which describes most colonial borders
- •Relict boundaries no longer have legal force and remain visible, like the line between the two Germanies, which is still detectable in voting patterns and infrastructure
The problem with rivers
A river looks like an ideal boundary and is a poor one, because rivers move. The law distinguishes two processes, and the distinction has decided real cases: accretion, the gradual shifting of a bank by deposition, generally moves the boundary with it, while avulsion, a sudden change of course in a flood, generally leaves the boundary where the old channel was. The Rio Grande has produced a century of disputes on exactly this basis, including the Chamizal tract at El Paso, which changed hands after the river shifted and took until 1963 and a presidential agreement to settle. Rivers also fail as boundaries for a social reason, since a river valley is usually a single community with the same language and economy on both banks, so a border along it cuts through a unit rather than between two. The stronger natural boundary is a watershed, which genuinely separates catchments and populations, which is why the Andes and the Pyrenees work better as borders than the Rhine or the Mekong.
Colonial lines
The African case is the clearest. The Berlin Conference of 1884 and 1885 set rules for European claims on the continent and was attended by no African representatives, and the boundaries that followed were agreed in European capitals, frequently by officials working from incomplete maps. The results split several hundred ethnic groups across borders, forced unrelated groups into single states, and created fifteen landlocked countries. Similar exercises produced the borders of the Middle East, where the Sykes-Picot agreement of 1916 divided Ottoman territory between British and French spheres, and the partition of India in 1947, where Cyril Radcliffe was given about five weeks to draw a line through Punjab and Bengal, had never visited India before, and worked largely from outdated census data; the resulting migration and violence killed somewhere between several hundred thousand and two million people. The striking fact about these lines is that they have almost all survived, because the African Union's predecessor adopted a principle in 1964 of respecting inherited borders, on the reasoning that opening any of them would open all of them.
How a border is actually made
The process has three technical stages that are frequently confused. Allocation is the political decision about which state gets what territory. Delimitation is writing the boundary down, in a treaty text and on a map, and this is where ambiguity enters, since a phrase such as the crest of the mountains or the main channel of the river has to be interpreted later. Demarcation is putting physical markers on the ground, which is expensive, and a very large proportion of the world's boundaries have never been demarcated at all. Disputes usually arise from the gap between stages: a treaty says one thing, a map attached to it shows another, and the ground matches neither. International tribunals resolve these by examining the treaty text, the maps, the conduct of the parties since, and the principle inherited from Roman law that a state succeeding a colonial administration inherits its administrative boundaries, which is how several African and Latin American cases have been decided.
Where they are still contested
Roughly a hundred land and maritime boundary disputes are active at any time, and several have specific well-documented causes. The line between India and China in the Himalayas rests on a boundary drawn at a 1914 conference that China did not ratify, and the two countries fought a war over it in 1962 and still hold periodic confrontations. Maritime boundaries have become more contested than land ones since the Law of the Sea Convention created two-hundred-mile exclusive economic zones, which turned isolated rocks into valuable assets because possessing one generates a zone around it, and which is the underlying driver of disputes in the South China Sea and the Aegean. Melting ice is producing new disputes in the Arctic, and it is also erasing some borders, since several alpine boundaries between Italy, Switzerland and Austria follow watersheds on glaciers that are retreating, forcing the states involved to adopt a moving boundary defined by whatever the ice does.
The takeaway
Boundaries are classified by what determined them, and geometric lines drawn from a distance cause far more lasting trouble than ones following watersheds or settlement patterns, which is why a third of Africa's borders are straight and Europe's are not. Rivers make poor boundaries because they move and because a valley is usually one community. A border passes through allocation, delimitation in a treaty and demarcation on the ground, and most disputes come from gaps between those stages. Maritime boundaries are now the most contested, since two-hundred-mile zones made isolated rocks valuable.