The 25 Atlantic Forest South-East Reserves contain some of the best and most extensive examples of remaining Atlantic forest in Brazil displaying the biological wealth and evolutionary history of the one of the world's richest and most endangered habitats. From mountains covered by dense forests, down to wetlands, coastal islands with isolated mountains and dunes, the area comprises a rich natural environment of great scenic beauty.
Partially isolated since the Ice Age, the Atlantic forests have evolved into a complex ecosystem with exceptionally high endemism (70% of the tree species, 85% of the primates and 39% of the mammals) and are considered to be among the world's richest forests for tree species.
The nominated site comprises the Serra do Mar Mountain Chain, which runs parallel to the Atlantic coast and separates the Brazilian high plateau (planalto) from the lower sea plains; part of the Estuarine Lagoon Complex of Iguape-Cananéira-Paranagua, which includes a great variety of wetlands, from the flooded plains of the Ribeira de Iguape River to saline waters of the lagoon complex itself. There is also a vast extension of beaches showing a succession of opened ocean-sand dunes.
The nominated World Heritage site contains well-preserved remnant patches of highly diverse and endangered Atlantic rainforest. More than 450 tree species per hectare can be found in some areas, indicating that the diversity of woody plants in the region is larger than in the Amazon rainforest. Major vegetation types in the site are tall mountain and lower mountain Atlantic rainforest. Forest canopy along river valleys is taller, with isolated trees reaching up to 30 m in height. Species composition and structure change with altitude, and transitional stages between forest types are linked to soil depth, fertility and humidity.
There is a highly diverse fauna with several species of conservation concern. Mammals include 120 species, probably the largest number in Brazil. Some noteworthy species are jaguar, ocelot, bush dog, La Plata otter, 20 species of bat and various species of endangered primate, notably muriqui and brown howler monkey. The newly discovered black-faced lion tamarin is endemic to the area. The avifauna is very diverse, with 350 recorded species. The area is an important breeding ground for harpy eagle, red-tailed Amazon and black-fronted piping guan, among many others.
More than 50 archaeological sites were unearthed in the area. These sites contain accumulation of shells, pottery and stone tools.