The arid and semi-arid climate of much of Southwest Asia creates biomes that are characterized by

Deserts and steppes.

Explanation:

Southwest Asia, also known as the Middle East, is one of the driest regions in the world. Its location, as well as the natural features in the region, prevent formation of humid air masses and precipitation, which in turn has made the region arid and semi-arid in general, with only very small parts stepping out of that.

Because the precipitation is so low, and the temperatures are very high, the biomes of this region are dominated by deserts and steppes. In other words, the landscape is dominated by rocky and sandy deserts, and by vast grasslands with short grasses. The diversity of the species both flora and fauna is pretty low.