Los Alerces

Los Alerces National Park, a UNESCO World Heritage Site since 2017, is located in the Andean Patagonia of Chubut Province, Argentina, covering approximately 263,000 hectares. The park is named for the alerce (Fitzroya cupressoides), one of the world's longest-lived tree species, ancient specimens of which grow in the park's dense temperate rainforest. The alerce is a Patagonian cypress related to the California redwood, and trees within the park are among the oldest living organisms in the Southern Hemisphere, with some individuals exceeding 2,600 years of age. The park encompasses a network of spectacular glacial lakes, including Lago Futalaufquen and Lago Verde, connected by channels and rivers in a remote Andean setting.

Los Alerces harbors significant populations of the endangered huemul deer, which inhabit the park's steep forested slopes and rocky terrains. Pumas are the apex predators. Pudús are present in dense forest understory areas. The rivers and lakes support the puyen (native Galaxias fish), the peladilla, and other endemic fish species alongside introduced trout. The critically important puyen population, threatened by introduced trout predation, represents a significant conservation concern. The park's bird community includes Magellanic woodpeckers, austral parakeets, Andean condors, and numerous waterfowl. American mink have invaded the waterways and severely impact native bird and fish populations.

The park's defining ecosystem is the Valdivian temperate rainforest, one of the most ecologically significant and least understood forest types in the world. The dominant trees are the alerce (Fitzroya cupressoides), whose ancient multi-stemmed individuals can reach 4 meters in diameter; coihue (Nothofagus dombeyi); mañío macho (Podocarpus nubigenus); and arrayán. The understory is dense with bamboo (Chusquea culeou), tree ferns, numerous mosses, and lichens. Above the tree line, Nothofagus pumilio (lenga) forms low wind-pruned thickets transitioning to subalpine meadows. The park contains the highest concentration of old-growth alerce forest remaining in Argentina, with some groves completely unlogged.

Los Alerces occupies a landscape shaped by intensive Pleistocene glaciation. The park's complex system of lakes occupies glacially carved basins; the longest, Lago Futalaufquen, extends for 55 km. The lakes are connected by rivers and channels, creating an inland waterway system navigable by small boats. The bedrock is composed of granites, schists, and other metamorphic and igneous rocks of the Patagonian Batholith, exposed by glacial erosion. Glacial moraines, outwash plains, and roches moutonnées are ubiquitous landscape features. Small active glaciers persist on the highest peaks in the park's western sector near the Chilean border. Post-glacial sediment accumulation in the lakes continues today.

Los Alerces has a cold oceanic climate with extraordinarily high precipitation on the Andean slopes. Western-facing slopes near the Chilean border receive 3,000–4,000 mm of annual rainfall, sustaining the ancient alerce forests. The eastern slopes in the rain shadow receive considerably less. Summer (December–March) offers mild temperatures of 15–22°C with long days and mostly clear skies. Winter brings heavy snowfall above 800 m, with temperatures dropping well below freezing. Strong westerly winds (the 'Roaring Forties') batter the western slopes year-round. The park's exceptional moisture creates the lush, mossy character of its ancient forests and sustains the waterways connecting the lakes.

Mapuche and Tehuelche peoples have inhabited the Patagonian Andes for centuries, using the forests, lakes, and rivers of the region. The alerce tree was used by indigenous communities for construction and canoe building due to its rot-resistant timber. European and Chilean settlers arrived in the late 19th and early 20th centuries. The alerce was intensively logged throughout Patagonia in the 19th and early 20th centuries—its highly prized, durable wood was used for shingles (tejuelas) throughout Chile and Argentina. This logging pressure was one of the primary motivations for the park's creation. Small farming communities established themselves in the river valleys adjacent to the park.

Los Alerces National Park was created in 1937, during the same period as Argentina's other major Andean national parks, primarily to protect remaining old-growth alerce forests from commercial logging that had already devastated much of the alerce's range in Chile and Argentina. The park's establishment halted logging within its boundaries, allowing the ancient trees to be preserved. In 2017, Los Alerces was inscribed on the UNESCO World Heritage List under criteria for outstanding universal value, recognizing both the exceptional natural significance of the alerce forests and the park's temperate rainforest ecosystems. The inscription has raised the park's international profile significantly.

The park's premier attraction is the 'El Abuelo' alerce—an ancient tree estimated to be over 2,600 years old, accessible via a scenic boat journey across Lago Verde followed by a short forest trail. Boat excursions across the lakes are the most popular activity, connecting the park's major bodies of water and providing access to remote forest areas. Trekking routes range from short walks near the visitor centers to multi-day circuits through the mountains. Fly fishing for trout is a major draw, particularly on the Río Arrayanes. The circuit of Lago Futalaufquen offers excellent lake-edge hiking through dense rainforest.

The park's main entrance and visitor center is at Villa Futalaufquen, approximately 50 km west of Esquel on Ruta 71. Esquel has an airport with connections to Buenos Aires and is the main service center for the region. Multiple campgrounds are distributed around the lakes, ranging from basic to well-equipped sites. The park's boat service (lanchas) operates from Villa Futalaufquen and connects to El Abuelo and other destinations. Accommodation includes hostels and cabañas in Villa Futalaufquen. Summer (December–March) is peak season. The park operates a strict visitor management system for the El Abuelo trail to protect the ancient alerce forest.

The UNESCO World Heritage designation underscores the global significance of Los Alerces' alerce forests and the responsibility Argentina bears for their protection. The primary conservation challenges include management of invasive species (American mink, introduced trout, and the North American beaver), protection of the endangered huemul, and managing growing tourism pressure. Beavers, introduced to Tierra del Fuego in 1946, have spread throughout Patagonia and cause devastating damage to riparian forests; active removal programs operate within the park. Conservation of native fish, particularly the puyen, requires intensive management of introduced trout populations. The park collaborates with Chilean protected areas across the border to manage shared ecosystems.