48
Spain, abundant regional sediment input is available, allowing high sedimentation rates to happen during the regeneration process and facilitating adaptation to
ongoing sea-level rise. Therefore, restoration of currently reclaimed tidal wetlands in global temperate coastal areas, with abundant sediment supply, can be
considered as a soft adaptation measure against climate change consequences in
the coastal zone.
Keywords Salt marsh • Sedimentary record • Human impact • Environmental
regeneration • Sea-level rise
2.1 Introduction
Salt marshes consist of a gently sloping vegetated platform, intrinsically linked to
the tides, as they develop between mean tide level (MTL) and highest astronomical
tide (HAT). Between these lower and upper limits, salt marshes can be subdivided
into elevational zones (i.e. low and high marsh) represented by vegetation changes
that respond to the duration and frequency of tidal flooding. Salt-marsh surface
elevation changes as a consequence of sediment accretion and compaction, being
the latter more influential as the salt marsh gets older. The elevation of the salt
marsh can also be affected by degradation of organic matter (Day et al. 2011;
Kirwan and Blum 2011), which represents one of the main components of sediment
accretion. In fact, salt-marsh vertical accretion is produced by sediment of allochthonous (i.e. fluvial and marine minerogenic and organic sediments) and autochthonous (i.e. plant organic matter) sources (Allen 2009). Vertical accretion is opposed
by autocompaction or loss of porosity caused by the weight of overlying sediments
(Bartholdy et al. 2010).
In northern Spain, these coastal ecosystems have been occupied initially with
agricultural purposes and later to support the more recent urban and industrial settlement, covering around 50% of the original salt-marsh extension (Rivas and
Cendrero 1991; Gobierno Vasco 1998). This human occupation has led to the
destruction, size reduction, and degradation of the environmental quality of these
coastal areas. Rivas and Cendrero (1991) conclude that human occupation of salt
marshes and other intertidal areas represents the main geomorphological change
occurred in northern Spain during the last two centuries.
Agricultural activities seem to be present in this coastal region since at least
5000 cal years BP (Zapata 2005/2006), although it was not until the beginning of
the 18th century that these activities significantly affected coastal wetlands.
During the last 300 years salt marshes have been drained and occupied, particularly intensely from the second half of the 19th century. Desiccation of salt
marshes was enhanced with the implementation of the Cambó Law in 1918,
founded on their suspected insalubrity (Gogeascoechea and Juaristi 1997). Since
A. García-Artola et al.
Spain, abundant regional sediment input is available, allowing high sedimentation rates to happen during the regeneration process and facilitating adaptation to
ongoing sea-level rise. Therefore, restoration of currently reclaimed tidal wetlands in global temperate coastal areas, with abundant sediment supply, can be
considered as a soft adaptation measure against climate change consequences in
the coastal zone.
Keywords Salt marsh • Sedimentary record • Human impact • Environmental
regeneration • Sea-level rise
2.1 Introduction
Salt marshes consist of a gently sloping vegetated platform, intrinsically linked to
the tides, as they develop between mean tide level (MTL) and highest astronomical
tide (HAT). Between these lower and upper limits, salt marshes can be subdivided
into elevational zones (i.e. low and high marsh) represented by vegetation changes
that respond to the duration and frequency of tidal flooding. Salt-marsh surface
elevation changes as a consequence of sediment accretion and compaction, being
the latter more influential as the salt marsh gets older. The elevation of the salt
marsh can also be affected by degradation of organic matter (Day et al. 2011;
Kirwan and Blum 2011), which represents one of the main components of sediment
accretion. In fact, salt-marsh vertical accretion is produced by sediment of allochthonous (i.e. fluvial and marine minerogenic and organic sediments) and autochthonous (i.e. plant organic matter) sources (Allen 2009). Vertical accretion is opposed
by autocompaction or loss of porosity caused by the weight of overlying sediments
(Bartholdy et al. 2010).
In northern Spain, these coastal ecosystems have been occupied initially with
agricultural purposes and later to support the more recent urban and industrial settlement, covering around 50% of the original salt-marsh extension (Rivas and
Cendrero 1991; Gobierno Vasco 1998). This human occupation has led to the
destruction, size reduction, and degradation of the environmental quality of these
coastal areas. Rivas and Cendrero (1991) conclude that human occupation of salt
marshes and other intertidal areas represents the main geomorphological change
occurred in northern Spain during the last two centuries.
Agricultural activities seem to be present in this coastal region since at least
5000 cal years BP (Zapata 2005/2006), although it was not until the beginning of
the 18th century that these activities significantly affected coastal wetlands.
During the last 300 years salt marshes have been drained and occupied, particularly intensely from the second half of the 19th century. Desiccation of salt
marshes was enhanced with the implementation of the Cambó Law in 1918,
founded on their suspected insalubrity (Gogeascoechea and Juaristi 1997). Since
A. García-Artola et al.