Climate Change and the European Water Dimension - Agri ...

Chapter IV. B. The Impact of Climate Change on Lakes in
Europe
IV. B.1. Introduction
If present trends continue, climatologists predict that the concentration of CO2 in the
atmosphere will have doubled by the year 2050 (McCarthy et al., 2001). This
increase will have a profound effect on the global climate and influence the seasonal
dynamics of lakes throughout Europe. To date, there have been relatively few
European studies on the impact of climate change on the dynamics of lakes. In
North America, there have been a number of such studies that also highlight the
geographic variation in the projected responses. These include studies on the
potential effects of climate change on the Laurentian Great Lakes (Magnuson et al.,
1997), the lakes of the Arctic and Sub arctic (Rouse et al., 1997) and the mountain
lakes of the Pacific coast (Melack et al, 1997). Recently the Arctic Council (2004)
published its report on “Impacts of a Warming Climate” also emphasizing the
dramatic changes occurring now in Arctic lakes.
In this review, potential effects of climate change on lakes in Europe are
summarized. European lakes have recently been the subject of intensive study in
several projects funded by the European Union (EUROLAKES, MANTRA-East,
CLIME, EMERGE, PHYTOPLANKTON ON-LINE, ECOFRAME, HMLS). This review
focuses especially on the products of the RTD FP5 project CLIME (Climate Impacts
on European Lakes) that started in 2003 and is due to end in 2005 and is mainly
based on data collected within this project and the foregoing project REFLECT from
three European regions: the Northern Region, the Atlantic Region and the Alpine
Region. Climate impact on lakes and reservoirs located in the Mediterranean region
and in Central and Eastern Europe are analyzed basing on published data.
In the review, our analysis of the impact of climate change is based on the output of
two contrasting Regional Climate Models (Räisänen et al., 2004) and an analysis of
the long-term changes recorded in a number of intensively studied lakes. Particular
attention is paid to the effects of the more extreme inter-annual variations in the
weather and the indirect as well as the direct effects of these climatic perturbations.
A number of investigators have already examined the effects of global warming on
water quantity (Boorman, 1997; Arnell, 1999) but very little attention has, hitherto,
been paid to the effects on water quality. The review includes a number of case
studies (Ch.VI.A) that illustrate some of the variations observed in four key lakes
listed as Primary Sites in the CLIME project (www.water.hut.fi/clime). These lakes
have been the subject of intensive study for more than 50 years and the observed
variations provide a good indication of the sensitivity of these lakes to the changing
climate.
IV.B.2. The Distribution of Lakes in Europe
Lakes are distributed unevenly in Europe. Norway, Finland and Sweden have
numerous lakes accounting for approximately 5-10 per cent of the surface area of
their repective countries (Table IV.B.1). A large number of lakes can also be found in
Baltic countries, in northern parts of Poland and Germany, in Denmark, Ireland and in
the northern and western parts of the United Kingdom. In Central Europe most
natural lakes are situated in mountain regions, the ones at high altitude being
relatively small and the ones in the valleys being the largest, examples being Lake
Geneva, Lake Constance, Lake Garda and Lake Maggiore in the Alps. Mountainous
Switzerland is especially rich in lakes. Generally, the percentage of lakes in the
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