The closure affects Fforest Fawr near Tongwynlais where public access will be restricted throughout February 2026 while Natural Resources Wales (NRW) undertakes essential tree work. The closure has been put in place due to the presence of ash dieback - a fungal disease that weakens and kills ash trees, leaving them at risk of falling without warning. "Ash dieback has significantly weakened many trees in Fforest Fawr, and removing them is essential to prevent the risk of falling branches or trees. The affected trees are located throughout Fforest Fawr, a popular woodland site featuring multiple walking trails. The work requires the use of large forestry machinery and extensive safety zones, making it unsafe to maintain public access during operations.