The floristic communities of the lomas formations essentially function as terrestrial islands separated by hyperarid habitat where virtually no plants exist. No fewer than 80 localities have been recognized as unique assemblages. A map of localities and a listing of individual lomas formations are provided. The plants within the lomas formations have diverse origins including amphitropic disjuncts, semi-arid Ecuadorian and central Chilean species, montane Andean disjuncts, and many lomas endemics. While the desert is continuous from Peru to Chile, the topography, climate, and vegetation of each desert is distinct.
Aridity is controlled by three climatic anomalies.
This pattern of temperature stability results from the influence of cool, sea-surface temperatures associated with the south to north flow of the Humboldt or Peruvian Current. Also important is the influence of strong atmospheric subsidence associated with a positionally stable, subtropical anticyclone. The result is a mild, uniform coastal climate with the regular formation of thick stratus cloud banks below 1000 m during the winter months. Click on the image for an enlargement. Where coastal topography is low and flat, this stratus layer dissipates inward over broad areas with little biological impact, but where isolated mountains or steep coastal slopes intercept the clouds, a fog-zone develops with a stratus layer concentrated against the hillsides.