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

Chapter VI.C. The Effects of Climate Change on Nutrient
Dynamics in the Po River Basin
VI.C.1 Introduction
Eutrophication in the Northern Adriatic is one of the major negative feedbacks
originating from the rapid socio-economic development that has occurred in the Po
region over the last decades. Nutrients released at river catchment level are carried
to the Adriatic Sea by several important rivers and of these the Po makes the largest
contribution. In order to mitigate eutrophication a reduction of the impact of
anthropogenic sources in the catchment is needed, however, it is well known that the
effects of nutrient reduction are non-linear and related to a dynamic interaction of
chemical, physical and biological processes acting on different temporal and spatial
scales in the atmospheric, water and soil ecosystems (Pirrone et al., 2005). Among
the external forces that can affect the nutrient cycle, climate change may play an
important role in the overall water cycle and affect pollutant transport pathways on a
river catchment - coastal zone continuum scale. Changes in temperature and
precipitation since the beginning of the 20 th century yield a global surface
temperature change of +0.6 ±0.2°C, with the sea surface temperature rise about half
that of the mean land-surface air temperature rise, a continued decrease in snow
cover and the extent of land-ice all suggest that global warming is a major driving
force that should be considered in long-term trend analyses of environmental
pressures acting at local to global scales. Since the 1960s the extent of snow cover
has decreased by about 10% and similarly the annual duration of lake and river ice
has decreased by about two weeks at mid- to high latitudes in the Northern
Hemisphere. The annual land precipitation has increased in the middle and high
latitudes of the Northern Hemisphere whilst it has decreased over the sub-tropics,
showing a strong relationship with annual stream flow. Recent studies suggest that
significant differences between regional patterns are primarily related to various
phases of atmospheric-oceanic oscillations such as the NOA and the ENSO (Avila et
al., 1996; IPCC, 1996; IPCC, 2001a).
Thus changes in catchment level nutrient dynamics may impact water quality in the
coastal zone. Warmer temperatures are expected to increase primary production,
accelerate nutrient cycling and organic matter decomposition leading to an increase
of terrestrial and marine vegetation growth. The foreseen contrasting trends in
precipitation due to changes in catchment hydrology will have a contrasting effect on
terrestrial vegetation and a significant impact on nutrient cycling, leading to an
increase in winter nutrient inputs and a summer decrease. Therefore in order to
identify optimal management strategies aimed at the reduction of CZ eutrophication,
there is a strong need to promote integrated catchment-coastal zone continuum
research to evaluate the effects on the nutrients cycle of the major driving forces
related to climate change.
VI.C.2. The Nutrient Cycle and the Climate Change
A preliminary assessment of the relative contributions of the major driving forces
related to climate change on nutrient dynamics in the Po catchment-North Adriatic
Sea continuum has been performed adopting the Driver-Pressure-State-Impact-
Response (DPSIR) approach. In the DPSIR analysis, major driving forces included
both human and pseudo-natural drivers (not properly natural because they are of
anthropogenic origin) (see Table VI.C.1). The nutrient loads (i.e. environmental
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