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Climatological, phenological and satellite studies revealed that the number of frost events has decreased and the growing season has lengthened in many regions of the world during the last decades. In general, the extension of the growing season has been associated with recent global warming and with large-scale atmospheric oscillations such as the North Atlantic Oscillation (NAO) and Artic Oscillation (AO). ). Observational analyses of air temperature data at global scales with respect to climate change confirm 0.76 °C rise since 1850. Warming since the 1990s has been particularly rapid with eleven of the twelve warmest years on record occurring since 1850 (IPCC, 2007). The growing season may be determined from phenological observations, the normalized difference vegetation index (NDVI) from satellite data and climatologically from surface air temperatures. Differently from the phenological growing season which defined period of actual growth of plants, the climatological growing season could be defined as the entire period in which growth can theoretically take place (Carter, 1998). As pheonological and NDVI studies, many other studies have reported on the lengthening and shifts in timing of the climatological growing season in the twentieth century as being associated with increasing temperatures. For North America, Skaggs and Baker (1985) found a general increase in the growing season's length in Minnesota between 1899 and 1982, where the last freeze events showed a general trend towards earlier and last freeze events towards later occurrence. Cooter and Leduc (1995) found that there was a significant trend towards an earlier initiation of the growing season over a large portion of the northeastern USA for the period 1961–1990. Easterling et al. (2000) indicated that for the period 1910–1998, there was a slight decrease in the number of days below freezing over the entire USA, although there was regional variation in the trends. Robeson (2002) reported that the length of the growing season in Illinois increased by nearly one week over the last 100 years. Spring freezes occurred nearly one week earlier, whereas the date of first fall appeared unchanged over the last century. Feng and Hu (2004) showed that there was a significant decrease of annual frost days in the western USA associated with lengthening growing degree-days and unchanged annual frost days in the eastern USA matched with the small changes in growing degree-day. Schwartz et al. (2006) found that over the 1955–2002 period the onset of spring started 1.5 days earlier per decade across most temperate Northern Hemisphere land regions.
Natural Environment and Culture in the Mediterranean Region The Mediterranean Basin is located at the intersection of two major landmasses, Eurasia and Africa, which contributes to its cultural and high biodiversity. The greatest impacts have been deforestation, habitat fragmentation, intensive grazing and fires, and infrastructure development, especially on the coast, which have distinctly altered the landscape. In view of the valuable natural heritage there is a great need for weighing our ecological impact in order to achieve a balance between biodiversity conservation and human development and above all, how to maintain traditional rural livelihoods in a way that benefits biodiversity. This book synthesizes knowledge from many disciplines to throw some light on the unpredictability of forthcoming changes.