Frevagh ASSI

This area is of special scientific interest because of its species-rich wet grassland.  Species-rich grassland tends to occur only where land management is not intensive, in particular where traditional farming practices have been maintained.  As a result, it is not a widespread habitat in Northern Ireland and is often fragmented, consisting of individual fields, parts of fields or banks.  Species-rich grasslands, like those found at Frevagh, are a particularly scarce resource in Northern Ireland.

The area covers the slopes of a small drumlin called Sour Hill which is situated within the townland of Frevagh, close to the Fermanagh-Leitrim boundary, 7km southeast of Garrison. Frevagh is in the marginal uplands with an altitude of approximately 100m above sea level.

The site is underlain by Carboniferous age limestones belonging to the Darty Limestone Formation and are some 335 million years old.  These rocks formed in relatively shallow marine environment and are base-rich having significant calcium carbonate content.  The soils at Frevagh are derived from the parent rock – the resultant soils have poor drainage characteristics.  

The western part of the site supports primitive (relatively shallow) but poor draining soils known as gleyed rankers while the eastern part of the site is dominated by deeper soils, also poorly draining,  known as surface water gleys.  Due to a combination of factors such as slope, altitude and the westerly geographical position, these soils are kept consistently moist. This combination of underlying geology, topography and the related soil hydrology has resulted in a complex range of species-rich wet grasslands within a small area.