THREE CONFLATED DEFINITIONS OF MEDITERRANEAN CLIMATES

Mediterranean climate" has in effect three different definitions: 1) climate of the Mediterranean Sea and bordering land areas; 2) climate that favors broad-leaved, evergreen, sclerophyllous shrubs and trees; 3) winter-wet, summer-dry climate. These three definitions frequently are conflated, giving rise to considerable confusion and misstatement in the literature on biomes, vegetation-environment relationships, and climate change. Portions of the Mediterranean region do not have winter-wet, summer-dry climate, while parts that do, may not have evergreen sclerophylls. Places away from the Mediterranean Sea, such as the Zagros foothills, have more mediterranean climate than anywhere around the Sea under the third definition. Broad-leaved evergreen sclerophylls dominate some regions with non-mediterranean climates, typically with summer precipitation maximum as well as winter rain, and short droughts in spring and fall. Thus, such plants may be said to characteristize subtropical semi-arid regions. On the other hand, where summer drought is most severe, i.e., the most mediterranean climate under definition 3, broad-leaved evergreen sclerophylls are rare to absent. Rather than correlating with sclerophyll dominance, regions of extreme winter-wet, summer-dry climate characteristically support a predominance of annuals, the life form best adapted to seasonal rainfall regimes. Given the importance of useful forecasting of vegetation and climate change under greenhouse warming, it is imperative that biome maps begin to reflect the complexities of vegetation-climate relationships.