Isla Chañaral is the biggest of the reserve's islands. Access to the island restricted by permit only. The island consists of two plateau levels. The main plateau between 50 and 70 meters above sea level is divided into a western and an eastern part by a second high plateau. The vegetation of the plateaus differs considerably. While the main plateau is dominated by shrub and cacti the high plateau has a barren appearance with only few small cactus aggregations.