The Lagoa de Óbidos is the largest coastal lagoon system on the Portuguese coast.

[citation needed] As a coastal lagoon system, the Lagoa de Óbidos holds high ecological value due to its productive characteristics, particularly in terms of ecosystem and species biodiversity.

[1] Of the entire lagoon area, the Braço da Barrosa is the most ecologically significant site.

It is crucial for various biological groups and hosts one of the few remaining patches of forest within the lagoon.

Additionally, it contains relatively well-preserved mudflat vegetation, which provides ideal conditions for birdlife and plays an important role for fish populations by offering suitable nursery habitats.