The Effects of Livestock Grazing and Recreation on Irish Machair Grassland Vegetation

Abstract

Machair grassland uniquely occurs over sandy, calcareous soils of coastal sand-plains in dune systems of north-western Scotland and Ireland. This study assesses the plant species composition of Irish machair grassland at a landscape-scale. Machair sites were sampled with quadrats and multivariate analysis was used to assess relationships between species abundance, soil physical variables, livestock grazing and recreation activity. Grazing by cattle and sheep was recorded at most sites, with recreation activities at nearly half the sites. Detrended and Canonical Correspondence Analysis ordinations showed that the main gradients of community composition were related to the key variables of soil calcium carbonate content, soil organic matter content, livestock grazing intensity and recreation pressure. Partial Canonical Correspondence Analysis showed that livestock grazing intensity and recreation pressure explained about twice as much variation as the key soil variables and that rabbit grazing had a much smaller but significant effect. Livestock grazing and recreation activities were shown to be ecologically damaging in terms of having a larger area of bare sand and a lower species diversity. Bare sand can increase the risk of storm damage and reduce habitat heterogeneity by sand-plain deflation. Controls on livestock density, the length of the grazing season and recreation activities are proposed, which we suggest would facilitate vegetation recovery. We highlight the need for local planning authorities, who control coastal development in Ireland, to include agricultural management prescriptions in their machair site management plans.