<P> Though precipitation increases with the height, there are semiarid conditions in the nearly 7000 m towering highest mountains of the Andes . This dry steppe climate is considered to be typical of the subtropical position at 32--34 ° S . The valley bottoms have no woods, just dwarf scrub . The largest glaciers, as e.g. the Plomo glacier and the Horcones glaciers do not even reach 10 km in length and have an only insignificant ice thickness . At glacial times, however, c. 20 000 years ago, the glaciers were over ten times longer . On the east side of this section of the Mendozina Andes they flowed down to 2060 m and on the west side to c. 1220 m asl . The massifs of Cerro Aconcagua (6,961 m), Cerro Tupungato (6,550 m) and Nevado Juncal (6,110 m) are tens of kilometres away from each other and were connected by a joint ice stream network . The Andes' dendritic glacier arms, i.e. components of valley glaciers, were up to 112.5 km long, over 1020, i.e. 1250 m thick and overspanned a vertical distance of 5150 altitude metres . The climatic glacier snowline (ELA) was lowered from currently 4600 m to 3200 m at glacial times . </P> <P> The Andean region cuts across several natural and floristic regions due to its extension from Caribbean Venezuela to cold, windy and wet Cape Horn passing through the hyperarid Atacama Desert . Rainforests and tropical dry forests used to encircle much of the northern Andes but are now greatly diminished, especially in the Chocó and inter-Andean valleys of Colombia . As a direct opposite of the humid Andean slopes are the relatively dry Andean slopes in most of western Peru, Chile and Argentina . Along with several Interandean Valles, they are typically dominated by deciduous woodland, shrub and xeric vegetation, reaching the extreme in the slopes near the virtually lifeless Atacama Desert . </P> <P> About 30,000 species of vascular plants live in the Andes, with roughly half being endemic to the region, surpassing the diversity of any other hotspot . The small tree Cinchona pubescens, a source of quinine which is used to treat malaria, is found widely in the Andes as far south as Bolivia . Other important crops that originated from the Andes are tobacco and potatoes . The high - altitude Polylepis forests and woodlands are found in the Andean areas of Colombia, Ecuador, Peru, Bolivia and Chile . These trees, by locals referred to as Queñua, Yagual and other names, can be found at altitudes of 4,500 m (14,760 ft) above sea level . It remains unclear if the patchy distribution of these forests and woodlands is natural, or the result of clearing which began during the Incan period . Regardless, in modern times the clearance has accelerated, and the trees are now considered to be highly endangered, with some believing that as little as 10% of the original woodland remains . </P> <P> The Andes are rich in fauna: With almost 3,500 species, of which roughly 2 / 3 are endemic to the region, the Andes are the most important region in the world for amphibians . The diversity of animals in the Andes is high, with almost 600 species of mammals (13% endemic), more than 1,700 species of birds (about 1 / 3 endemic), more than 600 species of reptile (about 45% endemic), and almost 400 species of fish (about 1 / 3 endemic). </P>

What is the most common type of vegetation in the andes