Mapping the habitats of the Republic of Croatia (2000.-2004.)- the project overview

At the end of year 2000, the Ministry of Environmental Protection and Physical Planning of the Republic of Croatia started the project ''Mapping the habitats of Republic of Croatia''. Three-year project was carried out by Oikon Ltd. Institute for Applied ecology from Zagreb, and finished at the beginning of year 2004. On the terrestrial part of Croatian territory data source for mapping were classified and interpreted Landsat ETM+ satellite images with the minimum mapping area of 9 ha, as well as results of intensive fieldwork. The spring and the autumn set of satellite images were simultaneously used. In the first step, each Landsat ETM+ scene was classified using supervised classification on the basic land-cover units. In the second step, each land-cover unit (on the each scene) was classified on the subunits using unsupervised classification supported by the optimisation of the number of clusters. Finally, the results of unsupervised classification were interpreted on the basis of field sample, additional spatial data sources and literature. Using the results of supervised classification, the variability of habitats represented by polygons was calculated and mapped using several indicators (number of present land cover types, Shannon-Wiener indeks of the present land cover types, proportion of the each land cover type, descriptive statistics in 3x3 and 5x5 neighbourhood around spatial elements with the area 30 x 30 m). The elongated habitats that usually do not exceed area of 9 ha were mapped as lines, using minimum mapping length of 300 meters. A potential distribution of rock and scree habitats was derived using digital elevation model. The habitats of inland watercourses were mapped in the three phases: 1) classifying those parts of watercourses for which a habitat type could be determined on the basis of literature and expert knowledge, 2) spatial prediction of habitat types for watercourses unclassified in the first phase, as a function of existing lithological and geomorphological data using neural networks as a modelling tool and 3) integration, harmonization and spatial generalization of results of the first two phases. The coastal habitats were mapped as a function of the coastal lithology and the spatial distribution of settlements along the coast. The infralittoral was mapped on the basis of spatial modelling in the framework of the raster-GIS, using neural networks as a modelling tool. Basic infralittoral habitat types determined on known locations represented dependant variable. As independent variables were used: 1) digital sea depth model produced by digitalisation and rasterisation of the cartographic original (nautical maps) in scale 1:100 000, 2) slope of sea bottom derived from the digital model, 3) distance from the coast, 4) mean seasonal sea temperature and bottom sea current magnitude obtained through a mathematical model and 5) specific spectral channels of the Landsat ETM+ satellite image (with the assumption that they are usable for the specified purpose in the photophilic zone). The lower border of the infralittoral was set up bathymetrically, as well as borders of circalittoral and bathyal. The circalittoral and bathyal have been mapped by overlapping the existing spatial data in the framework of the GIS, including: 1) lithologic map of the sea bottom in the scale 1:1 000 000, 2) map of the circalittoral biocoenoses in scale 1:3 000 000 and 3) bathymetry represented with the digital model. A web-oriented application, with possibilities of selection the habitat type and assigning the geographic position, was developed for the purpose of interactive on-line data input of localities, with the establishment of initial data base about habitat types on exemplary localities, including: 1) 932 terrestrial localities, 2) 1121 marine localities (1004 of infralittoral benthos and 117 circalittoral benthos) and 3) 25 localities of subterranean habitats. All types of the above-mentioned habitats were harmonised with the national habitats classification developed in the framework of this project. The map of habitats classified in this way was accompanied with newly developed colour scheme and prepared for printing using the official sections of 1:100 000 scale topographic sheets.