The Site is a mostly intact raised bog with classic hummock and pool formations over a large proportion of its surface. It features a very well-developed micro-topography of hummocks, pools and lawns, with the active core area being particularly wet. A variety of vascular plants, bog mosses and other bryophytes are found. Mongan Bog is important for its diversity of habitats, plant communities, birds and invertebrates. It is also an important location for biological monitoring and for research into raised bog ecology and restoration. The numbers of wintering greenland white-fronted goose (Anser albifrons flavirostris) and red grouse (Lagopus lagopus) have declined and there are no recent records for these species. However, the invertebrate fauna of the pools have been shown to be highly productive. Among the rare species found are four species of moths and the rare southern horsefly Chrysops sepulcralis. The “Living Bog” raised bog restoration project to raise water levels, rewet the bogs and increase the national extent of bog habitat was finalized in 2021. The main threats to the Site include disturbances from an adjacent railway, a few remaining drains and fire events.