a large number of plant and animal species of interest occur within the site, including most of the native irish mammal species, several important fish species including arctic char, and a range of rare or scarce plant species. several of the animal and plant species in the park have a hiberno-lusitanean distribution, meaning that they only occur in southwest ireland, northern spain, and portugal. the main reason for this is the effect of the gulf stream on southwest ireland's climate. the park has been designated a biosphere reserve because of the presence of such rare species.