The World Heritage properties in Spain include the last remnants of primeval beech forests in the Pyrenaic-Iberian Beech Forest Region, where the climate is warmer and drier in the lowlands.
In a continental humid climate and on nutrient-rich soils, these mountain beech forests are unique in this beech forest region. They mark the global western boundary of this type of mixed forest. The high ecological value combined with the complex topography of the property has prevented some of the stands from being managed or logged, apart from the occasional harvest for the local production of firewood.
There are three recognised beech forest areas in Spain. Hayedos de Ayllón is located on the Iberian Peninsula and is the only location outside the Pyrenees. The component parts here are enclaves on the south-western boundary of the beech forest and form small but important remnants within the global distribution area of the species. The property Hayedos de Navarra is located in the westernmost part of the Pyrenees and includes mixed fir-beech forests, which were left undisturbed due to a combination of inaccessibility of the site and historical factors. The World Heritage properties here are protected as strict nature reserves. The property Hayedos de Picos de Europa is located in the Atlantic biogeographical region and is a pure montane beech forest in an Atlantic climate with high humidity.