280
J osep Piiiol, Anna Avila and Antoni Escarre
Pinol et al. 1998). It seems also clear that the hydrological cycle will be accelerated as a consequence of the higher water holding capacity of warmer air,
which will increase evaporation and, consequently, precipitation. Nevertheless, the current predicting capability of general circulation models (GCMs)
linked with macro scale and landscape-scale hydrologic models that simulate
regional and local hydrologic regimes under global warming scenarios is still
poor. In spite of these uncertainties, all the predictions point to potentially
worsening conditions for flood control, water storage, and water supply in
areas of semiarid mid-latitudinal climates. Little information of this type is
currently available for other areas of the world (Loaiciga et al. 1996).
The water balance data of the experimental catchments of Prades and
Montseny were used by Pinol et al. (1995) to assess the effect of possible future changes of P and ET in the Mediterranean region on the main components of the water balance, Q and EA. The basic hypothesis was that the more
humid catchments of Montseny would change their behaviour toward the
currently observed behaviour at Prades. Simulations were presented showing
changes in the annual ET, EA, and Q in scenarios of increased temperature
( +2 and +4 °C) and variable annual precipitation (-10, 0, and + 1 0% of current P). Results suggested that in a warmer scenario, the Prades area would
hardly be able to maintain a closed-canopy forest such as the present one.
Curiously, the summer of 1994 was extremely warm and dry in eastern
Spain. During that dry spell, holm oak and pine (mainly Pinus sylvestris), the
dominant tree species of vast areas of Prades, were severely affected. The
long-term effect was much worse for pine than for holm oak, because of the
resprouting capacity of the latter that the former does not have. Other secondary species like Phillyrea latifolia were less affected. Lloret and Siscart
(1995) found similar mortality rates in holm oak and Phillyrea latifolia in
other areas of the region. Thus, if the climate becomes warmer and drier, it
would be possible for other species to take the dominant role of holm oak in
some areas with a present climate similar to that of Prades. These changes
would probably affect some water fluxes relevant at plot catchment scales,
like interception and transpiration. Nevertheless, when the uncertainty in regional estimates of rainfall and temperature increases and the possible shift
in species dominance are considered together, the prediction of hydrologic
fluxes at local and regional scales is highly inaccurate. At the present stage of
knowledge, hydrologic prediction at these spatial scales fits better in the field
of prophecy than in science.
J osep Piiiol, Anna Avila and Antoni Escarre
Pinol et al. 1998). It seems also clear that the hydrological cycle will be accelerated as a consequence of the higher water holding capacity of warmer air,
which will increase evaporation and, consequently, precipitation. Nevertheless, the current predicting capability of general circulation models (GCMs)
linked with macro scale and landscape-scale hydrologic models that simulate
regional and local hydrologic regimes under global warming scenarios is still
poor. In spite of these uncertainties, all the predictions point to potentially
worsening conditions for flood control, water storage, and water supply in
areas of semiarid mid-latitudinal climates. Little information of this type is
currently available for other areas of the world (Loaiciga et al. 1996).
The water balance data of the experimental catchments of Prades and
Montseny were used by Pinol et al. (1995) to assess the effect of possible future changes of P and ET in the Mediterranean region on the main components of the water balance, Q and EA. The basic hypothesis was that the more
humid catchments of Montseny would change their behaviour toward the
currently observed behaviour at Prades. Simulations were presented showing
changes in the annual ET, EA, and Q in scenarios of increased temperature
( +2 and +4 °C) and variable annual precipitation (-10, 0, and + 1 0% of current P). Results suggested that in a warmer scenario, the Prades area would
hardly be able to maintain a closed-canopy forest such as the present one.
Curiously, the summer of 1994 was extremely warm and dry in eastern
Spain. During that dry spell, holm oak and pine (mainly Pinus sylvestris), the
dominant tree species of vast areas of Prades, were severely affected. The
long-term effect was much worse for pine than for holm oak, because of the
resprouting capacity of the latter that the former does not have. Other secondary species like Phillyrea latifolia were less affected. Lloret and Siscart
(1995) found similar mortality rates in holm oak and Phillyrea latifolia in
other areas of the region. Thus, if the climate becomes warmer and drier, it
would be possible for other species to take the dominant role of holm oak in
some areas with a present climate similar to that of Prades. These changes
would probably affect some water fluxes relevant at plot catchment scales,
like interception and transpiration. Nevertheless, when the uncertainty in regional estimates of rainfall and temperature increases and the possible shift
in species dominance are considered together, the prediction of hydrologic
fluxes at local and regional scales is highly inaccurate. At the present stage of
knowledge, hydrologic prediction at these spatial scales fits better in the field
of prophecy than in science.