U.S. Soldiers in U.N. Operation in the former Yugoslavia Another type of transnational threat is the international diffusion of health and environmental problems. With increasing travel and migration, epidemics like AIDS have become global rather than local scourges. As the planet's resources are used more intensely, environmental problems spill over from one nation to another, and dangers to the global commons multiply. All nations are affected by global warming, loss of endangered species, and the depletion of the ozone layer. A third type of transnational threat is disruptive migration.
Many industrial societies feel that immigration is already at intolerable levels.
Deteriorating conditions in troubled states and increased access to information about the industrialized world will stimulate more migration. Mass exoduses resulting from political strife or natural disasters will sometimes require mobilizing the military for emergency relief. Large numbers of refugees could overwhelm attempts to control their movements, thus requiring military force to contain them. The world has been experiencing a wave of democratization since the late 1970s. In Latin America and Central Europe, democracy has become the norm, not the exception.