An Isolated Botanical World
Some 850 kilometers west of mainland Chile, the Desventuradas Islands—San Félix and San Ambrosio—are the exposed peaks of massive submarine volcanoes rising from the Nazca Plate. This extreme isolation has created a unique natural laboratory for evolution. The islands' flora is particularly distinct, with a remarkably high rate of endemism. Of the 22 native plant species found here, 19 are endemic, meaning they exist nowhere else on Earth.
The vegetation is a sparse, hardy scrubland adapted to the arid, windswept volcanic terrain. There are no permanent sources of fresh water. One plant is Thamnoseris lacerata, a shrub that can grow up to 5 meters tall in fog-dampened areas of San Ambrosio. The entire plant genus Thamnoseris is endemic to these two small islands. Other endemic plants include the succulent-leaved Suaeda nesophila and the woody shrub Frankenia vidalii. Genetic analysis suggests the ancestor of Thamnoseris likely dispersed here from the Juan Fernández Islands within the last three million years.
A Seabird Citadel Under Threat
The Desventuradas Islands are a critical breeding ground for seabirds. The most significant resident is the De Filippi's petrel (Pterodroma defilippiana), also known as the Masatierra petrel. This species, classified as Vulnerable, nests almost exclusively on these islands. In 1970, the colony on San Ambrosio was estimated at more than 10,000 birds. The petrels, along with other nesting seabirds, support the ecosystem; their guano enriches the volcanic soil, which supports the unique plant life.
This fragile ecosystem is threatened by non-native species. Feral cats have been introduced to San Félix, where they prey on nesting birds. Goats and rodents are also present on the islands, damaging the native flora through grazing and competing with native fauna. In response to these threats and to protect the unique marine environment, the Chilean government established the Nazca-Desventuradas Marine Park in 2015. Covering over 297,000 square kilometers, this fully protected "no-take" zone is one of the largest marine protected areas in the Americas.