Evolution of Forest Cover in Portugal: From the Miocene to the Present

Abstract

The transition of the Upper Oligocene throughout the Miocene was characterized by a cooling phase responsible for the extinction of several Palaeotropical taxa and the expansion of Arctotertiary taxa (Abies spp. Alnus spp.). Despite the dominant presence of sub-tropical, and tropical species in the Miocene these species were replaced in the Upper Miocene by large temperate forests of Populus, Salix, Carpinus, Castanea, Quercus , Acer, among others. During the Pliocene a progressive extinction of thermophyllous species and an increase in elements of the Mediterranean flora—Quercus, Olea, Ericaceae and Cistaceae occurred in the Iberian Peninsula. The Pleistocene cooling was responsible for profound changes in the Earth's flora and fauna, although the low latitude of the Iberian Peninsula spared several taxa. In Southern Europe some thermophyllous species (Sequoia, Taxodium, Keteleeria) were present until the Günz glaciation. In Portugal, the forests in the XII century were dominated by plants of the Fagaceae Family (Quercus spp and Castanea spp) but still with the presence of elements from the late Laurisilva. From the XII century onwards, forests underwent changes in their management, from protection until strong exploitation especially due to the maritime expansion and shipbuilding activities (XV and XVI centuries) and from 1636 onwards the demographic pressure. In the last quarter of the XIX century and beginning of the twentieth century afforestation programs were implemented throughout the mainland. In the last half century, industrial private forest (pulp and paper industry) had largely increased the area under Eucalyptus globulus, which reach at present 812,000 ha.