Environmental change in Crete: a 9000-year record of Holocene vegetation history and the effect of the Santorini eruption

Abstract

Palynological investigations were carried out in the coastal lowland of northwestern Crete, in the area of Lake Kournas. Results comprise the longest continuous vegetation record (9000 radiocarbon years) for Crete. From about 8500 to 7500 BP, open deciduous-oak forest occurred and appears to reflect the driest conditions of the Holocene. After 7500 BP, tree-pollen numbers increase. Some of these tree species are thought to be autochthonous, but for at least six species this is doubted and the presence of their pollen is ascribed to long-distance transport. Up to 6000 BP, the local vegetation included deciduous and evergreen oaks, Pistacia, Phillyrea and a variety of herbs. Only after 7000 BP, some species, e.g., Mercurialis annua, Cynocrambe and spores of Pteridium, might indicate the effects of Neolithic habitation. Towards 6000 BP, plane tree and Styrax (storax) appear; from about 6000 BP, olive is present and human activity becomes more evident. Slowly, pollen types indicative of the exploitation of present-day Mediterranean vegetation, e.g., Poterium and Ericaceae, appear and the presence of the alga Gloeotrichia indicates a rise in phosphate. A striking aspect of the sediment core nearest to the sea is a pumice layer originating from the Theran (Santorini) eruption. From the manner of its deposition it is concluded that no tsunami met the Cretan beach. Influence of the eruption from Thera on the vegetation is hardly visible. Decrease of economically important cultivated plants, e.g., olive, already took place decades, up to about a century, before the volcanic eruption. Around the time of the eruption, the values of some pollen types hardly changed, others increased and another group decreased. This pollen behaviour appears to be explained rather by socio-economic changes, such as withdrawing of the inhabitants to the interior for reasons other than volcanic effects. It is concluded from the pollen cores that no major climatic changes affected northwestern Crete during the Holocene but the first two millennia of the Holocene tended to be drier than the following period when there was an increase in moisture-demanding trees. It is difficult to assign changes in the Cretan vegetation to climatic effects in a period when human impact was gathering strength.

Vegetation dynamics in the Northeastern Mediterranean region during the past 23 000 yr: insights from a new pollen record from the Sea of Marmara

“…Cerealia type, Olea, Vitis and Juglans) and an overall increase in non-arboreal pollen (NAP). However, because all these pollen types can also be present in the natural vegetation, care must be used in the interpretation of pollen diagrams of the Eastern Mediterranean (Behre, 1990;Bottema and Woldring, 1990). Although occurrence of anthropogenic-pollen indicators may be highlighted by using high pollen sums (more than 1000 grains/sample), our record shows their presence during the entire Holocene, even though their abundance changes are only visible during the Late Holocene.…”

“…Conversely, a late reforestation (only after 8 ka) occurred in the drier parts of the Near East, in sites located in southernmost Europe, and in continental zones. This might be explained by a dry early Holocene where moisture levels were below the tolerance threshold for tree growth or a by a change from summer/spring to winter precipitation in sites located in Anti-Taurus-Zagros Mountains (van Zeist and Bottema, 1991;Stevens et al, 2001;Bottema and Sarpaki, 2003;Wick et al, 2003;Wright et al, 2003;Tzedakis, 2007;Djamali et al, 2010). We can conclude that the northern borderland of Southern Europe can be considered a transitional zone where the moisture level determined an earlier (ca.…”

“…2.1 cal ka (2.5-1.7 cal ka, accounting for five pollen samples) to which correspond increases of Poaceae, Caryophyllaceae, Sanguisorba minor type, Aster type, Cichorioideae, and Artemisia. Increases in pollen percentage of herbs were coupled with the occurrence of anthropogenic-pollen indicators (Behre, 1990;Bottema and Woldring, 1990), such as Cerealia type, Juglans and Olea that occurred since 3.1, 2.4 and 2.3 cal ka, respectively (Fig. 5).…”

The Sawflies of Crete (Hymenoptera, Symphyta)

“…Several other more recent events have at times been considered to be linked to a high rate of extinction in the Cretan flora and fauna, including for example the establishment of Neolithic culture 8400-7500 BP and the eruption of Santorini at around 3600 BP (Bottema and Sarpaki 2003). Recent studies do not support the hypothesis that the flora of Crete was devastated by ash deposition after the Santorini eruption (Bottema and Sarpaki 2003).…”

Paleoenvironmental evolution of Istron (N.E Crete), during the last 6000 years: depositional environment, climate and sea level changes

“…Interesting is the presence of Olea grains in Unit A as a big discussion has risen on whether this -typical Mediterranean-tree occurs in Crete by origin [29].…”