Monitoring the Responses of Freshwater Ecosystems to Climate Change - Climate Change Impacts on Freshwater Ecosystems - page 84

5
Monitoring the Responses of Freshwater
Ecosystems to Climate Change
Daniel Hering, Alexandra Haidekker, Astrid Schmidt-Kloiber,
Tom Barker, Laetitia Buisson, Wolfram Graf, G¨el Grenouillet,
Armin Lorenz, Leonard Sandin and Sonja Stendera
Introduction
Since 1970, freshwater biodiversity has decreased more drastically than marine
or terrestrial biodiversity (Loh & Wackernagel 2004). This is the result of a
complex mix of stressors and impacts (Stanner & Bordeau 1995; Malmquist &
Rundle 2002). The major drivers can be summarized as multiple use (such as
fisheries, navigation and water abstraction), nutrient enrichment, organic and
toxic pollution, acidification and habitat degradation. Climate change is adding
further stresses (temperature increase, hydrological changes) and interacts in
complex ways with existing ones (Travis 2003; Wrona et al . 2006; Durance &
Ormerod 2007; Huber et al . 2008).
As with other stressors, climate change will result in complex cause-effect chains,
the link between them provided by many interacting environmental parameters,
which are directly or indirectly influenced by temperature and precipitation. The
response of the biota is, therefore, less predictable than the response of chemical or
hydrological variables. On the other hand, biotic parameters such as species richness,
community composition or functional diversity integrate the complex effects of
many stressors on freshwater ecosystems, including those directly or indirectly
associated with climate change. This is the reason for using biotic communities
(such as phytoplankton, invertebrates or fish) for monitoring the ecological integrity
of European surface waters, as stipulated by the EU Water Framework Directive
(Heiskanen et al . 2004). The recently established Europe-wide monitoring
programmes, however, are mainly targeted at detecting the effects of those stressors
that have been dominant in the past, such as eutrophication, organic pollution,
acidification or hydromorphological degradation. Climate change is not specifically
targeted by the Water Framework Directive, though there is likely to be greater
pressure on European aquatic ecosystems in future because of it.