by the mutual consent of the states sharing the boundary. Such borders are quite
common in the Western Hemisphere, and some parts of Africa. Borders are also
drawn alongethnographiclines of division. These borders separate groups based
on distinctions in language or religiousaffiliation, and are the dominant kind of
political boundary in much of the world. New countries that have appeared on
the map in recent years have formed along ethnographic boundaries: Kosovo,
Timor-Leste, and Eritrea are all countries that have become independent since
1993, and are defined predominantly by ethnographic boundaries. It is often the
case that the borders between states are composed of all three types of these boun-
daries. The border between the United States and Mexico, for example, contains
segments that are both natural and geometric, and the entire length may be said
to represent an ethnographic boundary as well.
Political boundaries may also be classified in a system based on when the boun-
dary was established. The eminent political geographer Richard Hartshorne sug-
gested such a system in the early part of the 20th century. In this system, a
boundary that appears in a region that is devoid of settlement is termed apioneer
boundary. Such a boundary may become a relict boundary relatively quickly once
the region it lies within becomes inhabited or, on the other hand, may prove to be
resilient and continue to serve as a functional boundary for a considerable time.
Anantecedentboundary is one that is set prior to the establishment of the contem-
porary settlement pattern. Many of the boundaries in modern Africa are of this
type, because the colonial powers that pursued a policy ofimperialismthere in
the 19th century drew boundaries between their territories well in advance of any
Boundaries 39Hydropolitics
Water has become a scarce and precious resource in manyregions. Where bodies of water
are shared by more than one state, conflict may arise over the allocation of water. This is
increasingly the case where a river crosses an internationalboundary. Some of the world’s
major river systems have now become the focus of geopolitical tensions because of increas-
ingly pressures on the use of water. The Nile, Jordan, and Tigris-Euphrates river systems in
the Middle East, the Indus River in South Asia, and the Amu Darya in Central Asia all are at
the center of potential regional water conflict. It is not just thequantityof water that is at
issue, but often thequalityof water is a concern as well, especially if the water will be used
by humans or livestock for drinking. Growingpopulationsin some of the river basins where
friction is highest compound the problem, because the additional people of course require
additional water. Countries that pursue development on their stretch of the river, such as
building a hydroelectric dam for energy production, may instead generate tensions with a
downstream neighbor, who is concerned about reduction in flow. The politics of water will
likely be a major problem in the forthcoming century.