The River Barrow which flows through the town of Portarlington and down past Lea Castle is part of a large Special Area of Conservation under European law. The Rivers Barrow and Nore together are classified as the River Barrow & River Nore SAC.

The area is important for its wildlife as well as its history and archaeology, and all these factors must be considered in planning for the future of the castle.

This ecological report by Dr Fiona Mac Gowan describes the biodiversity of the area in and around Lea Castle. This is done by describing and mapping the habitats present and listing the plant and animal species recorded during a site visit in May 2014. The report also gives guidance on management issues on the site especially with reference to the SAC.

In addition a specialist bat report undertaken for the group by Scott Cawley in 2014 describes the bat populations around the castle.