This book present current research from across the globe in the study of the causes and impacts of forest decline. Topics discussed include the biotechnological approach to conservation of forest tree species; managing mangrove forest decline; ectomycorrhizas for forest resistance and resilience against factors of tree dieback; tree growth decline on relict Western-Mediterranean mountain forests; decline in the physical structure of deciduous hardwood forests due to deer grazing and drought and forest decline in the Iberian Peninsula.