The area shows a clear succession of habitats from riverside fen through to raised bogs, grading into wet woodland.
Because of this unique succession, the area supports a wide diversity of wildlife with large numbers of birds and mammals.
The marshes in the area are commonly flooded and the resulting alluvial soil supports an array of wetland vegetation.
The greater part of this area is the Biebrza National Park, covered by the Ramsar Convention to protect the wetlands and bird breeding grounds.
Particularly valuable is a large group of sedge-moss communities, containing many rare and relict species, disappearing in other parts of the country.