Juan Fernández Archipelago National Park is a protected area in the Pacific Ocean, located 665 kilometers west of Chile's mainland port city of San Antonio, within the Juan Fernández Archipelago. The park spans 96 square kilometers and includes the islands of Santa Clara, Alejandro Selkirk, and the most part of Robinson Crusoe Island.

Climate

The islands have a subtropical climate influenced by Mediterranean weather patterns, but this varies between islands. The cold Humboldt Current, which flows northward along the east side of the islands, and the southeast trade winds help keep temperatures less extreme. Temperatures range from 3°C (37°F) to 34°C (93°F), with an average annual temperature of 15.4°C (60°F). Areas at higher elevations are usually cooler, and occasional frosts occur on Robinson Crusoe.

On average, the islands receive about 1,081 mm (42.6 in) of rain each year, but this can range from 318 mm (12.5 in) to 1,698 mm (66.9 in) depending on the year. Rainfall changes a lot each year, and this is often influenced by the El Niño-Southern Oscillation. There is usually a dry season lasting 4 to 5 months during the warmer summer months. More rain falls in the winter months, and the amount of rain depends on elevation and which side of the island you are on. Areas above 500 m (1,640 ft) get frequent rain, but the western, leeward sides of Robinson Crusoe and Santa Clara receive very little rain.

Ecosystem of the park

The Juan Fernández Islands are home to many rare and unique plants and animals, some of which are in danger of disappearing, such as the Juan Fernández Hummingbird. These islands form a special area called an ecoregion. In 1977, UNESCO designated the entire archipelago, including Robinson Crusoe, Alexander Selkirk, and Santa Clara islands and all nearby islets within the national park, as a Biosphere Reserve.

The islands' volcanic formation and remote location keep them separate from the plants and animals found in mainland South America. This isolation means the islands have relatively few species of plants and animals. The closest relatives of the islands' species are found in the temperate forests of southern Chile, such as the Valdivian temperate rain forests, Magellanic subpolar forests, and the Desventuradas Islands.

There are 209 native vascular plant species in the park. About 150 are flowering plants, and 50 are ferns. Of these, 126 species (62 percent) are found nowhere else in the world, with 12 unique plant genera and one unique plant family, Lactoridaceae. Many plants are similar to those in Antarctica and are related to species in southern South America, New Zealand, and Australia. Vegetation types depend on elevation: grasslands and shrublands grow at lower elevations, tall and montane forests at middle elevations, and shrublands at the highest elevations. The two main islands have slightly different plant communities.

Alejandro Selkirk Island is mostly covered by grassland from 0 to 400 meters, with wooded areas (quebradas) containing dry forests of Myrceugenia and Zanthoxylum fagara. Between 400 and 600 meters are lower montane forests, and from 600 to 950 meters are upper montane forests. The tree line is at about 950 meters, where alpine shrubland and grassland dominate, with plants like Acaena, Dicksonia, Drimys, Empetrum, Gunnera, Myrteola, Pernettya, and Ugni. On Robinson Crusoe, grasslands cover the lowest areas (0–100 meters), followed by introduced shrubs (100–300 meters), tall forests (300–500 meters), montane forests (500–700 meters) with dense tree cover of Cuminia fernandezia, Fagara, and Rhaphithamnus venustus, tree fern forests (700–750 meters), and brushwood forests above 750 meters. Santa Clara Island is mostly grassland.

The Juan Fernández Goat is a major threat to native plants and contributes to the large grassland areas. These goats were originally domestic animals left behind by explorers and later became wild. CONAF works to manage this and other invasive species, such as mice, rats, birds, and cats.

Three endemic tree species dominate the montane forests: Drimys confertifolia on both main islands, Nothomyrcia fernandeziana on Robinson Crusoe, and Myrceugenia schulzei on Alexander Selkirk. Endemic tree ferns, such as Dicksonia berteriana on Robinson Crusoe and Dicksonia externa on Alexander Selkirk, and the endemic genus Thyrsopteris (T. elegans), are common in tree-fern forests. The endemic sandalwood species Santalum fernandezianum was overharvested and is believed extinct. The Chonta palm (Juania australis) is endangered.

The Juan Fernández Archipelago has few native land mammals, reptiles, or amphibians. Seventeen bird species breed on the islands, including three endemic birds and two endemic subspecies. Introduced species include rats and goats. Robinson Crusoe Island is home to the Juan Fernández Firecrown (Sephanoides fernandensis), an endangered hummingbird about 11 cm long with fewer than 500 individuals. Other endemic birds are the Juan Fernández Tit-Tyrant (Anairetes fernandezianus) and the Masafuera Rayadito (Aphrastura masafuerae). The islands support all known breeding populations of two petrel species, Stejneger’s Petrel (Pterodroma longirostris) and Juan Fernández Petrel (Pterodroma externa), both classified as vulnerable by the IUCN. A third petrel species, De Filippi’s Petrel (Pterodroma defilippiana), may also breed there.

The Magellanic penguin nests on Robinson Crusoe Island. The endemic Juan Fernández Spiny Lobster (Jasus frontalis) lives in the surrounding waters. The Juan Fernández Fur Seal (Arctocephalus philippii) also lives on the islands. This species was nearly wiped out in the 16th to 19th centuries but was rediscovered in 1965. A 1970 census found about 750 seals, and the population now exceeds 10,000. Only two seals have been seen on the Desventuradas Islands, located 780 km north, though their actual population may be higher due to hiding in caves. The population grows by about 16–17 percent each year.

• Juan Fernández Fauna and Sea Life
• Juan Fernández Reef
• Juan Fernández Wild Goat
• Juan Fernández Firecrown
• Juan Fernández Fur Seal

How to get to the park

From the continent, access is only possible by air or sea. By air, local airlines LASSA and ATA offer flights twice a week, taking about 2.5 hours from Santiago. By sea, a ship from the Chilean Navy visits the islands during December and February, and only sometimes during the rest of the year. The trip from Valparaíso takes about one and a half days.