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| Titel |
Human effects on estuarine shoreline decadal evolution |
| VerfasserIn |
A. Rilo, P. Freire, R. Ceia, R. N. Mendes, J. Catalão, R. Taborda |
| Konferenz |
EGU General Assembly 2012
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 14 (2012) |
| Datensatznummer |
250068471
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| Zusammenfassung |
| Due to their sheltered conditions and natural resources, estuaries were always attractive to
human activities (industrial, agriculture, residential and recreation). Consequently, the
complex interactions between anthropogenic and natural drivers increase estuarine shoreline
vulnerability to climate changes impacts. The environmental sustainability of these systems
depends on a fragile balance between societal development and natural values that can be
further disturbed by climate change effects. This challenging task for scientific
community, managers and stakeholders can only be accomplished with interdisplinary
approaches.
In this context, it seems clear that estuarine management plans should incorporate the
concept of change into the planning of policy decisions since these natural dynamic areas
are often under human pressure and are recognized as sensitive to climate change
effects. Therefore, the knowledge about historical evolution of estuarine shoreline is
important to provide new insights on the spatial and temporal dimensions of estuarine
change.
This paper aims to present and discuss shoreline changes due to human intervention in
Tagus estuary, located on the west coast of Portugal. Detailed margins cartography, in a 550m
fringe (drawn inland from the highest astronomical tide line), was performed based on 2007
orthophotos (spatial resolution of 0.5 m) analysis. Several classification categories were
considered, as urbanized areas, industrial, port and airport facilities, agriculture spaces, green
areas and natural zones. The estuarine bed (area bellow the highest astronomical tide line)
was also mapped (including human occupation, natural habitats, morpho-sedimentary units)
based on the geographic information above and LANSAT 7 TM+ images using image
processing techniques. Aerial photographs dated from 1944, 1946, 1948, 1955 and 1958 were
analyzed for a set of pilot zones in order to fully understand the decadal shoreline
change.
Estuarine bed presents an extensive intertidal area (146 km2), that includes 13% of salt
marshes and 1% of beaches. Anthropogenic structures such as salt pans, old tide mills or
aquaculture installations cover 15% of the intertidal zone.
Margins cartography indicates that natural areas (i.e regions that still preserve
their natural characteristics) correspond to 1% of margins total area (130 km2),
indicating that Tagus estuary has undergone great anthropogenic change. The most
important occupation types are the agriculture parcel (35%) and the urban area (34%).
Industrial zones, ports and airports facilities cover 24% and green spaces (areas with
vegetation in urban and non-urban zones, gardens, and leisure facilities) extend for
6%.
Preliminary results confirm that estuarine shoreline changes during the last 60 years are
mainly related with the direct effect of human activities in the intertidal zone, which
promoted the loss of natural areas such as beaches and salt marshes. Nevertheless, few
examples of natural recovery of abandoned areas by salt marshes can occur within the studied
period.
This paper brings to light the knowledge about the anthropogenic role in Tagus estuarine
shoreline decadal evolution, providing valuable information in future climate change effects
since it indicates that human occupation can be a barrier to the estuarine system natural
response. Furthermore it points out the relevance of planning occupation strategies in these
areas. |
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