Vegetation, water beetles and habitat isolation in abandoned lowland bog drains and peat pits

1. Multivariate analysis of vegetation and water beetles recorded in the abandoned drains and flooded workings of a cut‐over lowland Irish raised bog, Montiaghs Moss, shows that water depth and trophic status are key predictors of plant species composition and that vegetation community structure significantly explains water beetle composition. 2. The spatial distribution of secondary and tertiary drains and peat pits influences species composition indirectly, through trophic status, by connecting habitats with primary agricultural drains passing through the bog. 3. Habitat isolation and the cessation of drain management promote change in the submerged aquatic vegetation, emergent‐swamp and poor‐fen habitats recorded by facilitating vegetation development and surface acidification. 4. The ecological consequences are likely to be a reduction in the area of open‐water habitats, the development of poor‐fen vegetation and the subsequent loss of high conservation value species of plants and beetles. 5. Management for biodiversity conservation should initially address water quality, for example, through the European Union (EU) Water Framework Directive, followed by restoration to promote structural and spatial heterogeneity of drain and peat‐pit habitats. 6. At a landscape scale, implementing ditch and peat‐pit management across abandoned cut‐over lowland raised bog habitats in the farmed Northern Ireland countryside, through EU Common Agricultural Policy agri‐environment schemes, would give regional gains. Copyright © 2005 John Wiley & Sons, Ltd.