puna

The Quechua puna names the high-altitude grassland and shrubland ecosystem of the Andes, generally found between approximately 3,200 and 4,800 meters above sea level — above the treeline, below the permanent snowline, in the zone where the air is thin, the temperature swings violently between day and night, and the vegetation has adapted to ultraviolet radiation, frost, and fierce wind. The word passed into Spanish and then into scientific English as the standard term for this distinctive biome. Puna covers an enormous area: it is the predominant landscape of the Bolivian Altiplano, the Peruvian highlands, and the high Andes of Argentina and Chile, stretching across some of the most extreme terrain inhabited by humans anywhere on the planet.

The puna is not a uniform landscape but is divided by ecologists into sub-types: the wet or moist puna of the northern and central Andes, which receives more rainfall and supports dense tussock grass communities dominated by the ichu grass (Stipa ichu) and cushion plants; and the dry puna of the southern Altiplano, which grades into semi-desert conditions and is characterized by spiny shrubs and scattered grasses. Both are habitats for the wild camelids — guanaco and vicuña — that the Inca hunted and from which they developed their domestic animals. The puna is also the home of the puma, the Andean fox, the viscacha (a rabbit-like rodent), the Andean condor, and the flamingoes that breed in the extraordinary hypersaline lakes scattered across the Altiplano.

Human habitation of the puna is one of the more remarkable achievements of Homo sapiens as a physiological organism. The populations of the Altiplano — Aymara and Quechua speakers whose ancestors have lived at these altitudes for approximately 11,000 years — have developed genetic adaptations that allow them to function at oxygen concentrations that would incapacitate or kill an unacclimatized lowlander within days. These adaptations include modifications to hemoglobin, increased lung capacity, enlarged hearts, and, in Tibetan populations (the only other group with comparable altitude exposure), different but convergently evolved genetic pathways. The puna is the crucible in which these adaptations were forged.

The word puna entered English primarily through natural history and geography writing, particularly the accounts of 19th-century travelers and scientists exploring the Andes. Alexander von Humboldt described the puna ecosystem in detail in his Andean writings. Darwin encountered the puna ecology on his South American travels. The word became established in scientific literature as the correct term for this biome, distinguishing it from related but different high-altitude ecosystems such as the South African highveld or the Central Asian steppe. The term soroche — Quechua for altitude sickness — is closely associated with the puna, as this is the landscape where altitude sickness first dramatically announced itself to European travelers who had never before ascended above a few hundred meters.