EUROPE/Holocene 149 Holocene, the former prevailing tundra and steppe habitats (Figure 2) were nearly completely replaced by mixed deciduous forest (Figure 3) The first phase of tree invasion was characterised by birch and pine and later by hazel and elm The local tree assemblages could differ considerably from each other and also from recent compositions At around 10 000 years BP, in many parts of Europe the forest cover was still rather more open than at present, with more herbaceous glades By 9000 years BP, the forest had become closed, but with conifers more abundant Figure Vegetation zones in Europe during the Younger Dryas (A Ice; B Polar Desert; C Steppe Tundra; D Dry Steppe; E Semi Desert; F Wooded Steppe (Adapted from Adams 2002, with permission.) Figure Vegetation zones in Europe about 9000 years BP (A Ice; B Tundra; C Open boreal woodland; D Boreal Forest; E Deciduous/Mixed Forest; F Forest Steppe; G Moist Steppe; H Woodland; K Dry Steppe; L Mediterranean Forest (Adapted from Adams 2002, with permission.) than at present in eastern Europe Until that time, deciduous trees such as oaks or hornbeam were predominant or abundant, even in southern Europe (Figure 3) The typical recent Mediterranean vegetation with evergreen trees and shrubs started to develop after that time During the climatic optimum, thermophile plants and animals extended further to the north Possibly due to elm disease, a drastic decline in the number of elm pollen is observed in the geological records throughout Europe at about 5800 years BP Since 4500 years BP, there has been an increasing human influence on the faunal and floral elements of the European ecosystem Figure 4, showing the potential present vegetation without human influence, is obviously different from the coverage conditions today Another result of the changing Holocene climate was a rising global sea-level by meltwater supply and thermal expansion of sea-water (eustatic sea-level rise) During the maximum Weichselian glaciation, the global sea-level was about 125 metres deeper than today In the Early Holocene, large deglaciated areas started to uplift because of the vanishing ice load (glacio-isostasy) At the centre of the last glaciation, around the Bothnian Bay, an uplift of more than 280 m is recorded within Holocene sediments This isostatic uplift was compensated by subsidence in more distal regions (Figure 5) within the southern Baltic Basin By some authors, this process is assumed to be in the context of the collapse of an asthenospheric bulge in front of the retreating Weichselian ice shield (Figure 6) The combination of eustatic Figure Potential present vegetation zones in Europe (A Ice; B Tundra; C Open boreal woodland; D Boreal Forest; E Deciduous/Mixed Forest; F Forest Steppe; G Moist Steppe; H Woodland/Wooded Steppe; K Dry Steppe; L Mediter ranean Forest (Adapted from Adams 2002, with permission.)