264
However, the wetland system continued playing a fundamental role for migratory
birds and endemic biodiversity of central Chile until the beginning of the twentyfirst century. With the tsunami in 2010, it was clear that the construction of Rapel
dam was a serious disturb because it cut off the sediment supply that sustained
beaches and the dunes that protected this wetland. In many opportunities, this wetland was affected by quakes and tsunamis, intense ocean swell and ENSO, all phenomena able to dissipate their energy by destroying that natural barriers represented
by the dunes. Before the dam construction, the continuous sediment supply was able
to rapidly reconstruct the beach, sandbar and dunes, as was observed, for instance,
in Mataquito river mouth.
When the sedimentary supply was cutoff, the dunes still had enough material to
sustain the system equilibrium for some decades but when tsunami waves destroyed
these dunes, there was no material to recover neither the beach nor dunes. This generated a substantial change in the system, turning it more vulnerable to other (even
smaller) tsunamis, ocean swell, sea level rise associated to ENSO Kelvin waves, and
climate change. For this reason, the first proposed restoring action is to reconstruct
the dunes and reinforce them with a vegetal cover composed by native species,
which used to cover the dunes destroyed by the tsunami (Caldichoury 2002). The
other two steps are: (1) management of exotic forest species located around
Matanzas lagoon and that appear to increase the sensibility to water scarcity and (2)
planting native vegetal species around the waterbodies, as green fences that contribute to generate buffer areas in the wetland complex.
8.7 Discussion
As observed in records from around El Yali wetland, coastal wetlands in central
Chile are facing pressure from the contemporary climate change: Besides the rising
of the ambient temperature, the decrease of precipitations and the sea level rise, it
possible to observe an increase of the sea surface temperature, a decrease of nearby
rivers discharge, and a modification of the incident wave direction and significant
wave height. These effects are proved by fitting a linear trend with positive or negative slopes, depending on the particular variable (Figs. 8.3, 8.4, 8.5, 8.6, 8.7, and
8.8). However, due to the occurrence of ENSO, it is possible to distinguish an
important intra-annual climatic variability in those series. Years of intense precipitations are followed by years of hydric scarcity, due to the warm and cold ENSO
phases, respectively. However, this typical behavior has deviated during the present
century, where a strong El Niño occurred but has not been accompanied by intense
rainfall around El Yali. This explains the continuous decrease of the water surface
observed in the inner Matanzas lagoon (Fig. 8.13).
The delicate equilibrium at the Albufera was severely affected in two situations:
(a) the cutoff of the sedimentary supply after the damming of Rapel River in 1968
and (b) the removal of sediments from beach, sandbar and coastal dunes of El Yali
after the tsunami 2010. Thus a combination of anthropic alteration along with the
M. Contreras-López et al.
However, the wetland system continued playing a fundamental role for migratory
birds and endemic biodiversity of central Chile until the beginning of the twentyfirst century. With the tsunami in 2010, it was clear that the construction of Rapel
dam was a serious disturb because it cut off the sediment supply that sustained
beaches and the dunes that protected this wetland. In many opportunities, this wetland was affected by quakes and tsunamis, intense ocean swell and ENSO, all phenomena able to dissipate their energy by destroying that natural barriers represented
by the dunes. Before the dam construction, the continuous sediment supply was able
to rapidly reconstruct the beach, sandbar and dunes, as was observed, for instance,
in Mataquito river mouth.
When the sedimentary supply was cutoff, the dunes still had enough material to
sustain the system equilibrium for some decades but when tsunami waves destroyed
these dunes, there was no material to recover neither the beach nor dunes. This generated a substantial change in the system, turning it more vulnerable to other (even
smaller) tsunamis, ocean swell, sea level rise associated to ENSO Kelvin waves, and
climate change. For this reason, the first proposed restoring action is to reconstruct
the dunes and reinforce them with a vegetal cover composed by native species,
which used to cover the dunes destroyed by the tsunami (Caldichoury 2002). The
other two steps are: (1) management of exotic forest species located around
Matanzas lagoon and that appear to increase the sensibility to water scarcity and (2)
planting native vegetal species around the waterbodies, as green fences that contribute to generate buffer areas in the wetland complex.
8.7 Discussion
As observed in records from around El Yali wetland, coastal wetlands in central
Chile are facing pressure from the contemporary climate change: Besides the rising
of the ambient temperature, the decrease of precipitations and the sea level rise, it
possible to observe an increase of the sea surface temperature, a decrease of nearby
rivers discharge, and a modification of the incident wave direction and significant
wave height. These effects are proved by fitting a linear trend with positive or negative slopes, depending on the particular variable (Figs. 8.3, 8.4, 8.5, 8.6, 8.7, and
8.8). However, due to the occurrence of ENSO, it is possible to distinguish an
important intra-annual climatic variability in those series. Years of intense precipitations are followed by years of hydric scarcity, due to the warm and cold ENSO
phases, respectively. However, this typical behavior has deviated during the present
century, where a strong El Niño occurred but has not been accompanied by intense
rainfall around El Yali. This explains the continuous decrease of the water surface
observed in the inner Matanzas lagoon (Fig. 8.13).
The delicate equilibrium at the Albufera was severely affected in two situations:
(a) the cutoff of the sedimentary supply after the damming of Rapel River in 1968
and (b) the removal of sediments from beach, sandbar and coastal dunes of El Yali
after the tsunami 2010. Thus a combination of anthropic alteration along with the
M. Contreras-López et al.