Effects of agricultural and forest practices on biodiversity in North-West Spain

Resumo

Agricultural and forest practices affect biodiversity. In North-West Spain, the main land-use changes that have ocurred during the past 50 years are agricultural intensification and plantations of exotic tree species. This thesis focused on how agricultural and forest management practices, reflecting these changes, affect plants, butterflies and birds that depend on the agro-forestry environments of inland Galicia. The aims of the thesis were (i) to evaluate if and how birds benefited from organic farming, (ii) to evaluate if multiple aspects of butterflies and plants diversity benefited from organic farming, and (iii) to evaluate if and how Eucalyptus plantations affect biodiversity by comparing plant and bird species and diversity richness between native forest patches and exotic Eucalyptus plantations. Ultimately, the aim of the thesis was to propose ways to improve management of agro-forestry systems, in order to unite social interests and biodiversity conservation. The effects of farming and forest practices on biodiversity were analysed during three years by means of transects in paired organic and conventional farms, and native forests and Eucalyptus patches. Bird, butterflies and plant species richness, diversity and abundance were compared. Birds were shown to benefit from organic farming, as both species richness and abundance were higher in organic than in conventional farms. In addition, birds were also benefited by the presence of native forests surrounding organic farms. Butterfly species richness was higher in organic than in conventional farms. Furthermore, organic farming resulted in a higher functional diversity of butterflies. Finally, both plant and bird species richness and diversity were higher in native forests than in Eucalyptus plantations. Therefore, the results of this thesis suggest that both organic agriculture and native forests have a key role in biodiversity conservation, and that policies aiming for sustainable agricultural practices and conservation of native forests should be prioritized and promoted.