Along the Arctic coast, in the area of permanently frozen subsoil, or permafrost, is the tundra. Here mosses and lichens prevail. South of the tundra, stretching across the continent into Europe, is the vast northern coniferous forest, or taiga. Pines, firs, and spruces are the most common trees; larches are also abundant.
As rainfall decreases toward the heart of the continent, the taiga merges into treeless short-grass plains, or steppes. Farther inland, the steppes merge into deserts, which are virtually devoid of plants except in scattered oases. One of the most desolate areas is the Rub al Khali, or Empty Quarter, of the Arabian Peninsula. Along the Mediterranean coast are cypresses, oaks, and olives.
In the tropical areas of southeastern Asia grow luxuriant rain forests of tall broad-leaved evergreens and dense undergrowth. Similar vegetation is found in the wetter monsoon areas; inland these rain forests give way to deciduous forests and low scrub.
In the densely settled parts of Asia, particularly in India and China, most of the natural covering vanished long ago because of intensive cultivation.