Geography & Climate
The islands' land areas are very small, but their topography is extraordinarily rugged; geologically, the entire archipelago is a group of emergent peaks of the submarine mountain range known as the Juan Fernández Ridge, which goes east–west for more than 400km at the southern end of the Chile Basin.
The archipelago is far enough from the continent for subtropical water masses to moderate the chilly sub-Antarctic waters of the Humboldt Current, which flows northward along the Chilean coast. The climate is clearly defined with warm, dry summers and cooler, wet winters, though you'll need a jacket at night no matter the season.
The Juan Fernández fur seal is the only native mammal of the archipelago: they inhabit the seas and shores of Isla Robinson Crusoe and Isla Santa Clara. Of 11 endemic bird species, the most eye-catching is the Juan Fernández hummingbird (Sephanoides fernandensis). Only about 300 to 400 hummingbirds survive, feeding off the striking Juan Fernández cabbage that grows in many parts of San Juan Bautista, but the birds do best in native forest.
The archipelago is considered a unique eco-region with plants that slowly evolved in isolation, adapting to local environmental niches. Today, the greatest concentration of native flora survives in sectors where invasive plants and animals (including rats, rabbits, coatis and feral cats) can neither penetrate nor completely dominate.
Vegetation spans an extraordinary range of geographic affinities, from the Andes and sub-Antarctic Magallanes to Hawaii and New Zealand. Of 87 genera of plants on the islands, 16 are endemic, found nowhere else on earth; of 213 native plant species, 136 are endemic, making the islands 61-times richer in endemic plant species per square kilometer than the Galápagos. These plants survive in three major communities: the evergreen rainforest, the evergreen heath and the herbaceous steppe. Perhaps the most striking vegetation, however, is the dense understory of climbing vines and the towering endemic tree ferns Dicksonia berteroana and Thyrsopteris elegans.
To learn more about local efforts to protect this unique ecosystem, visit the website of Island Conservation (www.islandconservation.org/juan-fernandez-chile), a non-profit organization that works to prevent extinctions by removing invasive species from islands.