Limestone Grasslands – More Than Grass

Different types of management and climate conditions have resulted in a range of grassland types.

These range from high output perennial ryegrass swards to the low output, botanical - rich swards found predominantly in the west of Northern Ireland. Reseeded perennial ryegrass swards offer a high yield for the farmer helping to produce more milk or beef per hectare. However, they have minimal associated biodiversity with only three to four species per square metre.

Semi-natural grasslands on the other hand are those that have never been reseeded and received little or no fertiliser in the past. This type of grassland has lower levels of production but has a wide range of plant species and associated wildlife.

The limestone grasslands of Fermanagh are one type of semi-natural grassland. These occur on shallow, lime-rich soils and can have over 40 plant species per square metre. Typical species include wild thyme, mouse - eared hawkweed, lady’s bedstraw, kidney vetch and a range of orchids.

Kidney vetch, found on limestone and coastal habitats is the food source for Ireland’s smallest butterfly, called the small blue butterfly. This is Northern Ireland’s most rare butterfly now confined to just one colony in the Monawilkin area of west Fermanagh. Other populations existed on Islandmagee and the north shore of Belfast Lough in south Antrim, but these died out in the late 19th Century. A second Fermanagh colony was lost in the 1970s. The upperside of the butterfly is dark smoky grey with white fringing hairs, and the underside is silvery grey with numerous small black dots. The sexes differ little in size, with males showing a blue suffusion at base of wings on both sides. The cessation of grazing or intensification through increased fertiliser on this site would change the habitat and may result in the possible demise of this rare butterfly.

Agri-environment schemes, such as the Environmentally Sensitive Areas (ESA) Scheme or the Countryside Management Scheme (CMS), are the way forward for farming and the countryside. The payments to farmers under these schemes for fertiliser restriction and reduced stocking help to maintain these important habitats and compensate the farmer for the lower returns. Nearly 900ha of the estimated 1,000ha of limestone grassland in Northern Ireland is now under agreement and in the future with the right conditions we may even see another colony of small blue butterflies.