Central Andean Wet Puna: Glaciated Peaks, Cushion Bogs, and the Queen of the Andes

The Central Andean wet puna is a cold, moist, high-elevation grassland that runs along the Andes from northern Peru to northern Bolivia, above the tree line at roughly 3,500 m (11,500 ft). It forms a long, narrow, often fragmented band between the dry Sechura Desert on the west and the wet Peruvian Yungas on the east, a setting that produces abrupt transitions over short distances. To the north it gives way to the Cordillera Central páramo, and to the south to the Central Andean puna and the drier Central Andean dry puna, which our Puna article compares. In Peru, the ecoregion spans most of the departments of Huancavelica, Ayacucho, Apurímac, and Puno, and large parts of ten others, including Áncash, Junín, and Cusco; in Bolivia it occurs in La Paz Department.

Three Zones Above the Tree Line

WWF divides the ecoregion into three zones. The high Andean puna, between 4,200 and 5,000 m (13,780 and 16,400 ft), is the coldest, with summer by day and winter by night, frost every night of the year; and it receives less than 700 mm (28 in) of precipitation, mostly as snow and hail. The wet puna proper lies on the Altiplano between 3,700 and 4,200 m (12,140 and 13,780 ft), where average annual temperatures are only 5 to 7 °C (41 to 45 °F), nights are frosty from March to October, and 500 to 700 mm (20 to 28 in) of precipitation falls over eight wet months around Lake Titicaca but over only one or two in the south. The wet montane grassland covers the eastern flank between 3,800 and 4,200 m (12,470 and 13,780 ft), a landscape of steep mountains and deep glacial valleys that is more humid than the puna itself.

Ice-Carved Mountains and Lakes

Most of the bedrock is volcanic rock of Tertiary and Quaternary age, and ice shaped the rest. During the ice ages, much of the land above 4,000 m (13,100 ft) lay under ice, and glaciers descended as low as 3,000 m (9,850 ft), leaving moraines, glacial lakes, and, in northern Peru, deposits of wind-blown glacial dust up to 1 m (3.3 ft) deep. In the north, the wet puna is fragmented across the higher parts of lower ranges, including the Cordillera Blanca, Cordillera Negra, Cordillera Vilcabamba, and Cordillera Carabaya of the Peruvian Andes. In Bolivia, it follows the Cordillera Real, whose chains include the Apolobamba, Muñecas, La Paz, and Tres Cruces ranges. The ecoregion's highest peak is Nevado Huascarán, at 6,768 m (22,205 ft), and its largest lake is Lake Titicaca, at about 3,800 m (12,500 ft), which is fed on the Bolivian side by the Suches and Tiwanacu rivers.

Grasses, Cushion Bogs, and the Queen of the Andes

Bunchgrasses, wetlands, small shrubs, and herbs dominate the vegetation. In the high puna, grasses such as Festuca dolichopylla, Stipa ichu, and species of Calamagrostis grow among cushion-forming plants such as Azorella and Aciachne pulvinata. Wet ground below 4,000 m (13,100 ft) is covered by sedges and rushes of the genera Carex, Juncus, Oreobolus, and Scirpus, while above that elevation the bofedales are built by dense cushions of Distichia muscoides, Oxychloe andina, and Plantago rigida rooted in permanently saturated ground. Botanists have counted 1,000 to 1,500 vascular plant species on the Peruvian side alone, and the ecoregion is a center of diversity for the genera Culcitium, Perezia, and Polylepis. The only trees are Buddleja coriacea and several species of Polylepis, which form small woodlands in sheltered ravines and on rocky slopes.

The most striking plant is the Queen of the Andes (Puya raimondii), the world's largest bromeliad, a spiny rosette that grows for 40 to 100 years, by different estimates, before sending up a single flower spike up to about 15 m (50 ft) tall, typically 10 to 12 m (33 to 39 ft), and then dying. It is classified as Endangered and is endemic to the puna of Peru and Bolivia between roughly 3,000 and 4,800 m (9,850 and 15,750 ft). Peru's Titankayocc Regional Conservation Area may hold more than 450,000 plants, nearly half the species' total, and the plant also grows in Huascarán National Park.

Camelids, Predators, and Hibernating Bats

Four Andean camelids live in the wet puna: the vicuña (Vicugna vicugna), the guanaco (Lama guanicoe), and the domestic llama (Lama glama) and alpaca (Vicugna pacos), herded for centuries by Quechua and Aymara families. The vicuña, once close to extinction, has been protected since 1965 in the Ulla-Ulla reserve on the Peru-Bolivia border and in Peru's Pampa Galeras reserve, the first national reserve created for the species, and the wider story of its recovery is told in our Puna article. The puma (Puma concolor) and the culpeo, or Andean fox (Lycalopex culpaeus), are the main large predators, and two bats, the southern big-eared brown bat (Histiotus montanus) and the hoary bat (Lasiurus cinereus), hibernate to survive the cold.

Birds of the Polylepis Woodlands

The ecoregion's most threatened birds live in its remnant Polylepis woodlands. The ash-breasted tit-tyrant (Anairetes alpinus), a small flycatcher with a thin, forked crest, is classified as Endangered, and the royal cinclodes (Cinclodes aricomae) as Critically Endangered, with fewer than 300 mature individuals confined to a handful of woodland patches in southeastern Peru and in Bolivia's La Paz cordillera. BirdLife International attributes the threatened status of both species, among others, to the destruction of Polylepis woodland, and the extent of woodland around Cusco halved during the 1980s. Other restricted-range birds include Berlepsch's canastero (Asthenes berlepschi), a Vulnerable species confined to the slopes near Nevado Illampu; the Endangered plain-tailed warbling-finch (Microspingus alticola); the olivaceous thornbill (Chalcostigma olivaceum); the short-tailed finch (Idiopsar brachyurus); and the grey-bellied flowerpiercer (Diglossa carbonaria).

The Junín Puna

Around Lake Junín in central Peru lives a separate set of endemic birds, among them the flightless Junín grebe (Podiceps taczanowskii), the Junín rail (Laterallus tuerosi), the black-breasted hillstar (Oreotrochilus melanogaster), the dark-winged miner (Geositta saxicolina), the white-bellied cinclodes (Cinclodes palliatus), and the Junín canastero (Asthenes virgata). Pollution and changes in the lake's water level from mining operations have affected three of them, and the grebe's population has fallen sharply as the lake's frogs and fish have declined, even though the lake lies within a national reserve.

Protected Areas

Huascarán National Park, created in 1975, covers 340,000 hectares (840,000 acres) of the Cordillera Blanca, the world's highest tropical mountain range, with 27 peaks above 6,000 m (19,700 ft), hundreds of glaciers, and nearly 300 lakes; it became a UNESCO biosphere reserve in 1977 and a World Heritage Site in 1985. Farther south, Lake Junín National Reserve protects 53,000 hectares (about 131,000 acres), a 36,180-hectare (89,400-acre) reserve covers the Peruvian side of Lake Titicaca, and the Ulla-Ulla National Faunal Reserve, also a biosphere reserve, covers 150,000 hectares (about 370,700 acres) on the Peru-Bolivia border. Manú National Park, whose 1.53 million hectares (3.79 million acres) are overwhelmingly Amazonian forest, contains only about 18,400 hectares (45,500 acres) of puna; and in Bolivia, the Madidi and Apolobamba national parks protect part of the Cordillera Apolobamba, probably the most important area in the country for the ash-breasted tit-tyrant.

Pressures on the Puna

WWF counts the puna among the most altered regions of Peru and Bolivia. Grazing has gone on for centuries, and burning, firewood collection, and clearing for crops have also degraded the vegetation. Camelids, goats, and sheep graze the herbaceous plants so heavily that many cannot complete their life cycles, and overgrazing has caused soil erosion. Polylepis woodlands are cut for farmland and fuel, and mining has polluted lakes and poorly drained ground, threatening the aquatic and semi-aquatic plants that depend on them. At Huascarán, the IUCN's 2020 outlook identified climate change and the economic pressures on local communities as the main threats, and the retreat of the Cordillera Blanca's glaciers makes the region's water supply a growing concern.

Conclusion

The wet puna is a landscape defined by ice, water, and altitude, and its cushion wetlands, giant bromeliads, and relict woodlands depend on the same scarce resources that the highland herding and mining communities need. Protecting the Polylepis woodlands and bofedales, where the ecoregion's rarest species live, is the most direct way to protect the whole.

Map depicting the location of the Central Andean wet puna ecoregion (in purple).