Inland

temperature records indicate that the mean annual surface-air temperature of the Earth has risen approximately 0.6°C since 1860 (IPCC 2001). Increased global warming can have considerable influence at high latitudes, and among the major concerns are the effects on the sensitive arctic ecosystems and the possible reduction in the diversity of regional flora and fauna. Arctic organisms are highly adapted to extreme envi-ronmental conditions and have difficulties coping with any additional stresses or disturbances. In the ongoing palaeolimnological projects in West Greenland (Anderson & Bennike 1997; Brodersen & Anderson 2000) we address to what extent climate vari-ation has influenced the low-arctic West Greenland lakes during the Holocene. Palaeolimnological data provide independent information on the recent warm-ing, and also place the 19th to 20th century (instru-mental temperature records) warming in a long-term context. The sedimentary records allow us to look at the lake-specific ecological response to regional tem-perature fluctuations over the last several centuries to millennia. This perspective is an important capability in any aim to predict the possible outcome of late 20th century global warming. An important prerequisite, however, is to have good knowledge of the present lake-ecological conditions and the regional climate vari-ability in southern West Greenland, keeping in mind that West Greenland regionally has experienced a decline in average temperature in the second half of the 20th century (Heide-Jørgensen & Johnsen 1998; see also Mikkelsen et al. 2001, this volume). Recent limnology and palaeolimnology Most groups of plants and animals respond more or less directly to the ambient temperature and climate con-ditions. The non-biting midges (Diptera: Chironomidae) 59 Holocene temperature and environmental reconstruction from lake sediments in the Søndr