Grazing capacity change on a small Mediterranean-type South African offshore island following the control of invasive alien European rabbits (Oryctolagus cuniculus)

Invasive alien species (IAS) are one of the most important factors driving extinction rates worldwide. Among the IAS, the impacts of introduced mammals on native biodiversity are most severe, with the European rabbit (Oryctolagus cuniculus) being the most problematic. Globally, European rabbits have been introduced to five continents and more than 800 islands or island groups where they are a threat to biodiversity and human livelihoods. The impacts of European rabbits on biodiversity and human livelihoods have been extensively studied across the globe. However, some regions of the world, such as the offshore islands along Africa’s southern coast, have been sparsely studied. In this study, we monitored change in grazing capacity on a South African offshore island, Robben Island, following an attempt to eradicate European rabbits between 2008 and 2009. Grazing capacity on the island increased following rabbit control, driven by the recovery of palatable plant species in response to release from herbivory. There was no change in grazing capacity at sites under Eucalyptus plantations because of the inhibitory effects of the alien trees on understory vegetation dynamics. We believe that grazing capacity changes on Robben Island are indicative of potential vegetation changes on other southern African offshore islands.

外来入侵物种（Invasive Alien Species, IAS）是全球范围内驱动物种灭绝速率上升的最重要因素之一。在外来入侵物种中，外来引种哺乳动物对本土生物多样性造成的影响最为严重，欧洲兔（*Oryctolagus cuniculus*）则是其中问题最突出的物种。全球范围内，欧洲兔已被引种至五大洲及800余个岛屿或岛群，对当地生物多样性与人类生计构成威胁。全球范围内，欧洲兔对生物多样性及人类生计的影响已得到广泛研究。然而，全球部分区域，如非洲南部沿岸的近海岛屿，相关研究仍较为匮乏。本研究针对南非近海岛屿罗本岛，监测了2008至2009年间实施欧洲兔根除行动后的载畜量变化情况。经兔类防控措施干预后，岛上载畜量有所提升，这得益于适口性植物物种因脱离植食压力而得以恢复。而在桉树人工林分布区域，载畜量未发生明显变化，原因在于这些外来乔木对林下植被动态产生了抑制作用。我们认为，罗本岛的载畜量变化可作为南非南部其他近海岛屿植被潜在变化的参考指征。