Climate and hydrology - Mediterranean Mountain Environments - page 94

some of the lowest specific discharges and highest input from snowmelt, thereby
rendering them particularly vulnerable even for 'business-as-usual' climate and an-
thropogenic scenarios. These data require improvement in future projects through
various monitoring techniques.

5.2.3 Snow and water quality

Apart from the quantity of water, the quality of water derived from snow is of ma-
jor importance. Thus the chemical and radiochemical quality of snow requires de-
tailed examination (Villa et al., 2006). Agricultural fertilizers and other chemical
substances that were used in past decades and have since been prohibited were
transported in the atmosphere, then condensed, precipitated and concentrated in
snow at higher altitudes. With rapid temperature increases due to global warming
in recent years, snow is melting faster than usual including the older snow layers.
Thus the polluted substances that were 'locked' in the snow are re-emerging over
short time periods in the meltwater flow with unusually high concentrations. In
addition, very high levels of radioactivity can be measured in the snow and in the
groundwater derived from snowmelt in the Alps and other mountain regions such as
the Apennines. Because the Chernobyl accident of May 1988 was associated with
widespread snowfall or rainfall in the Alps, the radioactivity levels at high altitudes
are to this day persistently high. However, the spatial distribution of radioactivity is
much more heterogeneous in the mountains than on the plains. The release of such
substances through ablation of the older snow cover can substantially influence wa-
ter quality and limit the availability of water for human consumption.

5.2.4 Ecohydrology

Snow- and rainfall-derived water quality and quantity have important effects on
aquatic ecology, such as streams and lakes, since temperature and substrate stabil-
ity strongly influence macroinvertebrate community structure in alpine snow- and
glacier-fed streams (Castella et al., 2001). Aquatic ecology is much more vulnerable
than terrestrial ecology to physical impacts. According to Ricciardi and Rasmussen
(1999), aquatic faunas are five times more vulnerable to extinction than terrestrial
faunas. Literature on this topic is sparse and confined to the Alps but it is necessary
to extend this field of study and ensure that attention is given to the relations be-
tween aquatic biodiversity and economic values (such as water quality and tourism).
Mediterranean mountain forests are particularly dynamic ecosystems that in-
fluence the hydrological cycle in terms of evapotranspiration, condensation, dis-
charge and snow retention. Forest and forest watersheds play an essential role in
sustaining and protecting water supplies (FAO, 2004;, Garcia-Santos et al., 2005).
However, mountain biodiversity has been strongly negatively affected by the on-
going trends in agricultural decline (Mitchley et al., 2006). The change in forest