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I. Duarte & F.C. Rego 2010. Land use changes in Portugal between 1990 and 2005
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However, with the XXI century arrival, it matters to understand if the trends are maintaining or,
if something changed in the land-cover relation with society.
With this study, we pretend to identify (1) the main changes in land use in Portugal between
1990 and 2005, (2) the general trends and (3) the dynamic relationship between the land use
types.
2. Methodology
We used as a basis for study two cartografic elements: Carta de Ocupação de Solo -1990
(COS90) from the responsibility of the Portuguese Geographic Institute (IGP) and the National
Forest Inventory 2005 (IFN05) of the National Forest Authority (Ministry of Agriculture and
Fisheries). However, these mappings have been developed with different objectives. The first,
inspired in the nomenclature of CORINE landcover, aims to give greater accuracy and detail to
the Corine coverage, in Portugal (Caetano et al, 2007), assumed at the time as a tool to support
planning studies, and decision making. IFN05 was conceived for supporting policies and forest
management (DGRF, 2007).
Thus, COS90 is presented on the form of polygons and is based on a alphanumeric information
legend as type of occupation, first and second dominant species and a reference to density. In
this map we obtain the total of 638 different land use type combinations. The IFN05, is
presented on the form of 334390 points, in a grid of 2km for 2km, covering all continental
Portuguese territory. This legend, also alphanumeric, but with a different nomenclature, was
established for purposes of identification of type of use, dominant species, second and third
dominant species, vertical structure, density and presence of other uses. Overall, we obtain 2163
land use type combinations.
Methodology begans on data transformation in order to compare both cartografic elements. We
used ArcGis 9.3 program package, to join tables, getting a grid of points with the information
contained in each of the mappings in accordance with their original captions.
Then we reclassified all the 334390 points, covering the whole territory, for the year 1990 and
for the year 2005, with a general common nomenclature. This new classification was based, on
the first level, on the type of land use: Forest, agriculture, shrublands, other (artificial) and
wetlands. On the second level, considered the dominant specie (forest) or type of agriculture. In
the class shrublands were included also clear cut, burnt, sown and young plantation areas as
well as recently soil mobilized. We removed wetlands and remaining 328029 points.
The comparability has made possible, such as the construction of the transition matrix, using the
Microsoft Office Excel 2007.
3. Results
To identify the land use changes between 1990 and 2005, we produced a transition matrix that
explains the alterations between classes, showed in table 1. With this matrix, and figure 1
support, we can clearly verify the (1) significant increasing of shrublands, (2) the visible
increase of Eucalyptus, irrigated agriculture and artificial occupancy, and (3) the losses of Pine,
Cork & Holm oaks and unirrigated and other agricultures.
The persistence index calculated was only 51%. This means that 49% of Portuguese territory
suffered a transition for one other class, during the 15 years in analysis.
Forest Landscapes and Global Change-New Frontiers in Management, Conservation and Restoration. Proceedings of the IUFRO Landscape Ecology
Working Group International Conference, September 21-27, 2010, Bragança, Portugal. J.C. Azevedo, M. Feliciano, J. Castro & M.A. Pinto (eds.)
2010, Instituto Politécnico de Bragança, Bragança, Portugal.