A review of natural vegetation openness in north-western Europe

Secondary succession is threatening many species of open habitats in north-western Europe. This problem has caused an intense debate over whether the present-natural vegetation in this region would be closed forest or more open vegetation. Native large herbivores have been proposed as the key agents creating such open vegetation. Here I address this question by reviewing the palaeoecological evidence regarding vegetation openness in past oceanic interglacials and the pre-agricultural Holocene, i.e. before the onset of strong human impact. I conclude that closed forest would predominate, but include localized longer-lasting openings. Further, open vegetation would be frequent on floodplains, infertile soils, chalklands, and in continental and submeditteranean areas. Large herbivores and fire emerge as likely potential key factors in creating open vegetation in north-western Europe. Fire would probably also be important in the maintenance of light-demanding or short-statured woody species within closed upland forests.