Contradiction in Conservation of Island Ecosystems: Plants, Introduced Herbivores and Avian Scavengers in the Canary Islands |
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Authors: | Laura Gangoso José A Donázar Stephan Scholz César J Palacios Fernando Hiraldo |
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Institution: | 1. Department of Applied Biology, Estación Biológica de Do?ana, C.S.I.C., Avda Ma Luisa, E-41013, Sevilla, Spain 2. Casa Sick-Esquinzo, E-35626, Morro Jable, Fuerteventura, Spain
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Abstract: | Introduction of alien herbivores in sensitive island systems has resulted in massive effects on vegetation cover, floristic
richness and composition of communities; some species can be even totally extirpated by grazing pressure. Goats Capra hircus and wild rabbits Oryctolagus cuniculus were introduced in the Canary Islands around 500 B.C. Barbary ground squirrels Atlantoxerus getulus were introduced in 1967. Traditional extensive livestock exploitations have been maintained to the present but in the last
decades the number of goats has sharply increased up to densities of 53 heads/km2. Overgrazing and trampling have heavily affected eleven island endemic plant species. Some populations have been reduced
to less than 10 viable individuals. On the other hand, goat carcasses and wild rabbit and squirrel populations help to maintain
populations of three endangered endemic subspecies of birds. This conflict presents important economic and social ramifications:
whereas public funds (mainly through European LIFE projects) are devoted to conservation of plant and avian endemic taxa,
the number of goats increases rapidly thanks to subventions derived from the European Common Agricultural Policy (CAP). Similar
conflicts are apparent in other Mediterranean Basin insular systems. It is urgently necessary to harmonize farming and conservation
objectives in the Canary Islands. The impact of goats on the vegetation should be minimized through limitation of grazing
in sensitive areas with high degree of endemism. Creation of ‘vulture restaurants’ may reduce the dependence of scavengers
on extensive livestock exploitations. We recommend a careful study of ecological relationships within island communities where
non-native species are susceptible of playing a keystonrole as occurs in the Mediterranean Basin archipelagos. |
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Keywords: | Agricultural policies Avian scavengers Endemism Herbivores Islands Vegetation |
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