The Atlantic Forest is the second largest plant formation in all of South America following the Amazon Forest. At the time of colonization, the forest extended from the state of Rio Grande do Norte (about 6oS) to the state of Rio Grande do Sul (about 30oS, or 3250 km, or 2000 miles), and widening in the state of Paraná to the border of Brazil, Argentina and Paraguay at Iguassu Falls.
The Atlantic Forest was the first environment settled by the Portuguese colonists more than 500 years ago, and today still has about 70% of the entire Brazilian population, mostly in the very large cities of São Paulo, Rio de Janeiro, Salvador and Curitiba. Because of these historical processes, since colonization, about 93% of the original Atlantic Forest domain was deforested or extremely modified in some way.
Because of the varied altitudes of the mountains and the width of the coastal plains, the Atlantic Forest houses a very wide variety of different environments that are subsets of the forest. These include restinga (the Brazilian word for the less-dense forest of sandy coastal soils), mangrove forests, coastal forests, montane forests, Paraná Pine forests (mixed or dominated by the pine), and high-elevation meadows. This fascinating forest has around 20,000 species of plants, and one can find up to 450 species in a single hectare (2.5 acres, about the size of a football field). And among those many plants can be found an estimated 2,200 species of birds, mammals, reptiles and amphibians.
The Atlantic Forest, being isolated from other forests (the Cerrado and Caatinga separate it from the Amazon Forest), also became a region known for its high levels of endemism. The distributions of many species of all kinds are within the domain of the Atlantic Forest and found nowhere else on earth.