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This optional theme considers two different kinds of extreme environment:

Cold and high-altitude environments (polar, glacial areas, periglacial areas, high mountains in non-tropical latitudes)

Hot, arid environments (hot deserts and semi-arid areas) 

These environments are relatively inaccessible and tend to be viewed as inhospitable to human habitation. Despite this, they provide numerous opportunities for settlement and economic activity.

This theme examines the essential landscape characteristics of the two kinds of extreme environment, together with the natural processes operating in them, and the way in which people have responded to the opportunities they offer and the challenges they pose for management and sustainability.