Exploring environmental variables based on ecotopes derived by remote sensing
LifewatchWB contributes to the European Research Infrastructure Consortium for biodiversity and ecosystem research (Lifewatch) by providing online tools for the visualization of environmental variables. It consists in two Web portals (www.uclouvain.be/lifewatch) providing data about i) weekly anomalies of the dynamic land cover properties (snow cover and vegetation greenness) and ii) high resolution characterization of ecotopes. The topic of this abstract is the ecotope visualization interface. Ecotopes are the smallest ecologically functional units. They can be mapped by intersecting a large number of thematic layers (soil type, land cover, topographic types). However, this creates a lot of polygons with an exponentially increasing number of categorical values combinations. The visualization and analysis of those polygons is therefore difficult. On the other hand, the LifewatchWB ecotopes consist in irregular polygons derived from geographic object-based image analysis (grouping adjacent pixels of similar properties to create a partition of irregular polygons). Each polygon is then characterized using a set of continuous fields: quantitative variables (climate, elevation, slope, artificial light, contextual variables…) are either interpolated or averaged at the level of the ecotopes depending on the resolution of the input layers; categorical variables (soil types, land cover types…) are provided as proportions inside the ecotopes. The ecotope database is an open data layer currently available for the Walloon Region (Belgium). It consists in 1.2 million polygons with more than 80 quantitative fields. Those fields cannot be visualized together, therefore several visualization tools are provided on the interface: 1) each variable can be visualized individually in grey level, 2) any set of three variables can be visualized as a color composite and 3) queries based on potentially all variables can provide binary outputs. In addition, an online tool is available to extract the values of the ecotope characteristics in a set of point locations for further analysis in other softwares. With its polygon-based structure that is homogeneous with respect to the land cover and the topography, ecotopes provides meaningful landscape units with a large set of precomputed variables. Those variables are easy to visualize in a WebGIS and have been combined with species observations to run habitat and biotope models.