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

(mainly sand) from the river. After centuries of growth, the trend in sediment
deposition at the delta area over the last hundred years has reversed, due to the
construction of several dams regimenting the flow, so that dynamic equilibrium
between river deposition and wave transport has shifted towards prevailing sea wave
erosion.
The geological evidence for the past 10,000 to 20,000 years indicates that major
temporal and spatial variation occurs in relative sea level change (e.g. figure VI.C.6,
Pirazzoli, 1991) on time-scales of the order of a few thousand years. Potential global
rise of sea level has been predicted by the IPCC (2001) to range between 0.2 and
0.82 m by the year 2100. It is generally recognized that the synergistic effects of
subsidence of the delta, due to reduced sediment deposition, coupled with sea level
rise, could be a major threat to the continued, long-term existence of the unique
habitat present in the Ebro delta and, in the end, to the existence of the delta system
itself. On one hand saline water wedging would be enhanced; on the other hand
decreased freshwater and solid discharge and increased nutrient concentration
would lead to chemical pollution, increased eutrophication, water salinity and
temperature increase, finally affecting the species composition of the various
microenvironments of the delta area (macrophites, benthos, fish, etc.).
Present
Figure VI.C.6. Average sea level change in the past 2500 years (Pirazzoli, 1991).
Survival of large wetland areas would also be threatened. Those are areas where
the vertical growth range of vegetation is very small, so that even slight increases in
water level would have the potential of flooding or even sweeping away vegetation,
leading to the complete disappearance of marsh ecosystems (Sǎnchez-Arcilla et al.,
1996).
Assessment of potential impacts of climate changes in the Mediterranean region,
based on several case studies, have been carried out by UNEP/MAP and include
drought, floods, changed soil erosion, desertification, storms, coastal erosion,
seawater temperature and salinity currents together with sea level rise and
biodiversity reduction. Recent paleoclimatic data collected in geologically stable
areas, combined with archaeological or historical evidence, indicate that sea level
increase for the next century (2100) could be limited to 30 cm, taking into account the
pace of anthropogenic enhancement of sea level rise. Such a scenario is compatible
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