Calcareous Grasslands are species-rich grassy areas that develop on thin layers of lime rich soil over a limestone bedrock. In order to be classed as 'species rich', more than 20 different species must be present within a 4m2, there must be less than 20% scrub cover, and there must be characteristic plant species for the habitat. There is approximately 936 hectares of calcareous grassland in Northern Ireland, a figure which is taken from a survey conducted between 1992 and 1997.
In Northern Ireland the majority of calcareous grassland is in the hills of County Fermanagh, with smaller fragmented patches found in County Antrim. It is generally found at heights over 150m. Like many other important habitats, it has undergone significant decline in recent years, but there is very little data available to tell us exactly how much. This decline can be mainly attributed to scrub invasion or changes in management to more intensive practices. One of the problems with loss of calcareous grassland is that it is very slow to recover after damage.
On the plus side, many of the areas where it is found are of no use for other purposes such as other agricultural practices or road building/development due to where they are geographically, so in this way are less at risk than other grassland habitat.
Calcareous grassland is a very important habitat for many species, particularly butterflies. There are many Northern Ireland priority species found here, such as Irish hare, skylark, the 'small blue' butterfly (Cupido minimus), dingy skipper butterfly (Erynnis tages), Irish eyebright (Euphrasia salisburgensis), dense flowered orchid (Neotinea maculate), the hoverfly (Cheilosia ahenea) and the mosses Tortella densa and Myurella julacea. Of these species, Irish eyebright, dense-flowered orchid and autumn gentian are found nowhere else in the British Isles.