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Invasive Terrestial Flora & Fauna of Macaronesia. TOP 100 in Azores, Madeira y Canarias.
Recent studies have shown that Macaronesia has considerable problems with exotic species, particularly those considered as invasive. For instance, in the Azores more than 60% of the vascular plant flora consists of non-indigenous species (Silva & Smith 2004, 2006). Several plants are presently considered to be serious threats not only to the conservation of the Azorean endemic flora and native plant communities, but also to the conservation of bird species, namely the Azores bullfinch (Pyrrhula murina) and of arthropods (Borges et al. 2006). In Madeira Archipelago, species like the black rat (Rattus rattus) and the domestic cat (Felis silvestris catus) are known to have a strong negative impact on populations of native birds. In the Canaries, about 11% of the terrestrial biota corresponds to alien species, and some recent introductions originated some social alarm, namely the recent naturalization of a species of snake (Lampropeltis getula) in Gran Canaria. However, of the considerable number of introduced species, how many are considered as really invasive (i.e. they are not only naturalized but are presently causing a negative impact on the Macaronesian biota)? Among those species, which are amenable to control or eradication? Which species should be considered priorities for control actions and other measures because they are causing impact but are still possible to control or eradicate? For instance, in Canaries the Barbary ground squirrel (Atlantoxerus getulus) is considered an emblematic invasive alien species (IAS), but is it the top-ranking invader in Macaronesia? French Hydrangea (Hydrangea macrophylla) is a touristic icon in the Azores, but is now also considered as an invasive alien species. What is the real impact of the different species of alien rodents in Macaronesia? Although negative impacts have been a concern, should positive impacts also be considered? For example, several alien species still have and will most probably continue to have an important role in the islands’ economy or as game species. This book aims to answer some of these questions. It is a first attempt to present information regarding alien species in the European region of Macaronesia in a systematic way. Undoubtedly, this is a difficult task, due to differences regarding legislation but also to the differences in the general treatment given to IAS in the different archipelagos. A standard set of criteria was designed and applied to those species considered as naturalized and occupying natural and semi-natural habitats. A first set of criteria was used to score the effect on biodiversity values, in terms of species and habitats, which are being affected by the invasive species. A second set of criteria was used to score the feasibility of control or eradication of the invasive species. In this second set of criteria we also included items reflecting the social importance of the species concerned. The application of both sets of criteria has allowed identification of the most noxious IAS in Macaronesia and also the ranking of those species according to a management priority. This is of considerable importance, since, due to the large scale of the IAS problem not only in Macaronesia but globally, it is not possible to control every introduced species. Resources will have to be allocated to those species that are still possible to control or eradicate with sustainable costs. Although the criteria were applied by experts from each archipelago, a global Macaronesian approach was possible after a thorough analysis and careful treatment of the data from each archipelago, this being the main objective of the book. This book is also intended to serve as a tool to raise awareness of the problem of IAS. In fact, island ecosystems have been considered as more susceptible to IAS than continental systems, largely due to the small scale of the islands and to peculiarities of island biota which make them more susceptible to foreign competitors, predators and pathogens. However, islands, particularly European islands, are important hotspots for biodiversity, and the preservation of this natural heritage is currently also dependent on the implementation of effective measures to contain IAS