Setting

The ecoregion covers and area of 11300 square kilometres (4,363 sq mi) on the Atlantic coast of Maranhão

Maranhão

Maranhão is a northeastern state of Brazil. To the north lies the Atlantic Ocean. Maranhão is neighbored by the states of Piauí, Tocantins and Pará. The people of Maranhão have a distinctive accent...

 and eastern Pará

Pará

Pará is a state in the north of Brazil. It borders the Brazilian states of Amapá, Maranhão, Tocantins, Mato Grosso, Amazonas and Roraima. To the northwest it also borders Guyana and Suriname, and to the northeast it borders the Atlantic Ocean. The capital is Belém.Pará is the most populous state...

 states. The ecoregion is divisible into eastern and western parts. The western part extends from near Belém

Belém

Belém is a Brazilian city, the capital and largest city of state of Pará, in the country's north region. It is the entrance gate to the Amazon with a busy port, airport and bus/coach station...

 on the Pará River

Pará River

The Pará River is the southern arm of the mouth of the Amazon River. It flows round the west and south of the island of Marajó. It takes some water from the main Amazon, however much of its power comes from the Tocantins River flowing from the south. The state capital of Pará, Belém, is located on...

 along the coast of eastern Pará and western Maranhão states to the Baía de São Marcos

Baía de São Marcos

The Baía de São Marcos is a bay of the Atlantic Ocean in Maranhão state of northeastern Brazil.The bay is an estuary approximately 100 kilometers long and up to 16 kilometers wide. It receives several rivers, including the Grajaú, Mearim, and Pindaré...

. Here the coastline is made up of hundreds of islands and mudflats, made up of fine silt deposited by the Amazon River

Amazon River

The Amazon of South America is the second longest river in the world and by far the largest by waterflow with an average discharge greater than the next seven largest rivers combined...

.

The eastern part extends from the Baía de São Marcos along the eastern coast of Maranhão to the mouth of the Parnaíba River

Parnaiba River

The Parnaíba River is a river in Brazil, which forms the border between the states of Maranhão and Piauí. The Parnaíba River rises in the Chapada das Mangabeiras range, and flows northeastward for 1,056 miles to empty into the Atlantic Ocean. The middle and upper regions of this river are...

. Here the coast is dominated by extensive sand dunes, interspersed with pockets of mangroves in bays and river mouths.