Annually laminated sediments from Lake Van, spanning about 13000 varve years, were sampled for stable-isotopic, geochemical, pollen and charcoal analyses in order to find evidence of past regional climatic changes and human impact in the semi-arid region of eastern Anatolia, Turkey. The Lateglacial period was cold and dry, with steppe vegetation and saline lake water. During the Younger Dryas the lake level dropped dramatically, and the vegetation tumed to a semi-desert. Geochemical and isotopic records indicate a strong increase in moisture at the onset of the Holocene, and Arteinisia-chenopod steppes were partly replaced by grass steppe and pistachio scrub. A delay of about 3000 years in the expansion of deciduous oak woodlands and high steppe-fire frequencies suggest dry spring and summer weather during the early Holocene. At 8200 yr BP, a shift in the regional climate regime facilitated the transport of more moisture into the interior areas of the Taurus mountains and caused a change in the seasonal distribution of precipitation. The steppe-forests dominated by Quercus advanced and reached their maximum extention at about 6200 yr BP. All the proxy data indicate optimum climatic conditions, low water salinity and high lake level between 6200 and 4000 yr BP. After 4000 yr BP, aridity increased again and the modern climatic situation was established. Human impact in the catchment of Lake Van started at 3800 yr BP and was intensified during the last 600 years.

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Lake Ohrid in southeastern Europe is one of the few ancient, long-lived lakes of the world, and contains more than 200 endemic species. On the basis of integrated monitoring of internal and external nutrient fluxes, a progressing eutrophication was detected (,3.5-fold increase in phosphorus (P) concentration in the lake over the past century). The lake is fortunately still oligotrophic, with high concentrations of dissolved oxygen (DO) in the deep water that are requisite for the unique endemic bottom fauna. Hypolimnetic DO is not only very sensitive to changes in anthropogenic P load-via mineralization of organic material-but also to global warming via decrease of vertical mixing and less frequent complete deep convection. Moreover, these two human effects amplify each other. To keep DO from falling below currently observed minimal levels-given the predicted atmospheric warming of 0.04uC yr 21 -the P load must be decreased by 50% in coming decades. However, even with such a reduction in P load, anoxia is still expected toward the end of the century if the rate of warming follows predictions.

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