Grazing by goats released onto small islets is a particularly damaging practice all across the globe. One reason is that the flora on small islands generally has evolved in the absence of herbivores. As a result, local plant species tend to lack the chemical (e.g. bad-tasting compounds) and mechanical (e.g. thorns) defenses used to reduce consumption by herbivores. In addition, it appears that once introduced to an island, livestock keep nesting seabirds away, therefore eliminating critical marine nutrient subsidies (i.e. fertilizer in the form of guano and food scraps). In an ongoing project (spearheaded by Z. Gizicki) we try to understand the magnitude and the reversibility of such impacts.
Typical vegetation structure on an ungrazed Mediterranean islet.
The narrow-range endemic Helichrysum amorginum on the sea cliffs of Anydro Isl. (Cyclades, Greece).