As in southernmost Chile, thick southern beech forests cover the Argentine sector of Tierra del Fuego. Along the coast, the deciduous lenga (Nothofagus pumilio) and the Magellanic evergreen coigüe (Nothofagus betuloides) are the main tree species; at higher elevations, the stunted, deciduous ñirre (Nothofagus antarctica) forms nearly pure stands. In some low-lying areas, where cool annual temperatures inhibit complete decomposition, dead plant material compresses into sphagnum peat bogs with a cover of ferns and other moisture-loving plants; the insectivorous Drosera uniflora swallows unsuspecting bugs.

Argentina’s first coastal national park, Parque Nacional Tierra del Fuego has a seashore protected by thick kelp beds that help incubate fish fry. Especially around Bahía Ensenada and Bahía Lapataia, the shoreline and inshore waters swarm with cormorants, grebes, gulls, kelp geese, oystercatchers, flightless and flying steamer ducks, snowy sheathbills, and terns. The black-browed albatross skims the Beagle’s waters, while the Andean condor sometimes soars overhead. Marine mammals, mostly sea lions but also fur seals and elephant seals, cavort in the ocean. The rare southern sea otter (Lutra felina) may exist here.

Inland areas are fauna-poor, though foxes and guanacos are present in small numbers. The most conspicuous mammals are the European rabbit and the Canadian beaver), both of which were introduced for their pelts but have proved to be pests.