The promontory includes a marsh with unique plant and animal life on the shore of the Adriatic. The brackish marshes are fed by several streams whose water mixes with the seawater. Various types of sea grasses grow here, as do plants such as the lesser pond-sedge. The area is one of Slovenia’s primary nesting grounds for the European shag. The bounty of life extends well inland, where the grasses give way to a typically Mediterranean forest. Meanwhile, flysch cliffs rising from parts of the coast provide visitors with impressive views. The cliffs are topped with Mediterranean pines and surrounded by indigenous oak trees.
In many ways, the man-made landscapes of Debeli Rtič are just as interesting as those created by nature. The hilly parts of the promontory are covered with vineyards belonging to the Vinakoper wine estate. Meanwhile, an arboretum established in 1955 features trees from around the Mediterranean and beyond. The diverse species range from kiwi trees and persimmons to more typically Mediterranean stone pines, Australian acacia, cedars, and Himalayan pines. In total, about 230 different species of trees and shrubs can be seen in the arboretum.
In 1991, plans for a gas terminal threatened the unique ecosystem. In order to stop any such projects, the local authorities had the promontory officially protected. In 2018, Debeli Rtič received additional protection when the state declared it a Landscape Park – in recognition that this little-known stretch of the coast is one of the most biotically diverse places in Slovenia.