ABSTRACT
High mountains exist on all continents, on many islands, and in all latitudes. Elevation interacts with latitude as well as with permanent snowline so that relatively low mountains at high latitudes or near stormy middle-latitude coastlines can be "alpine" in a "high-mountain" sense. Islands have been buffered by surrounding seas against invasions by plants and animals; high mountains are similarly buffered by "seas" of surrounding lowland deserts, grasslands, or forests. Extreme cases in the evolution of alpine and montane ecosystems occur on high mountains on oceanic islands. In the large mountain systems, such as the American Cordillera, once plant and animal taxa have migrated up into the high mountains and evolved adaptations to the alpine environment, many of the species are able to migrate and join other high mountain ecosystems. Primary productivity in an ecosystem is the rate at which solar energy is captured by the vegetation per unit area of land surface or water volume.
