 Rainfall is higher in the winter months, and varies with elevation and exposure; elevations above experience frequent rainfall, while the western, leeward sides of Robinson Crusoe and Santa Clara are quite dry.The Juan Fernández islands are home to rare and endemic plants and animals, some of which are at risk of extinction (like the Juan Fernández Hummingbird).The islands are recognized as a distinct ecoregion, and the whole archipelago, including Robinson Crusoe, Alexander Selkirk and Santa Clara islands and all the islets in the area of the national park, were designated a Biosphere Reserve by UNESCO in 1977.