Modelação espacial da adequabilidade de habitat a espécies invasoras: o Carpobrotus Edulis em terreno não dunar

Resumo

The use of habitat modelling for exotic invasive species can be extremely useful for identifying their potential impacts and for assisting in the design of eradication strategies. Even though the latter builds on theoretical assumptions that are quite different from those involved in the modelling of the habitat of native species, these two modelling methods are in fact quite similar. This article presents a habitat suitability modelling framework for Carpobrotus edulis, an alien invader plant in Serra do Bouro, Portugal. Several land surveys have been carried out in the study area in order to record the presence of this plant. The criteria for recording a presence were that the plant did not show any signs of weakness and that there were mat formations covering at least 5m2. Pseudo-absences were also obtained in a completely random way. The model was calibrated using a binary logistic regression. The performance of this model usually considered superior to that of models that rely on presence data only. Additionally, an evaluation technique based on the minimum area of higher adequacy is also presented. This technique assumes that, for a given probability threshold, model performance is higher whenever it has the same number of correct presences for a smaller predicted area. Using a 0.7 probability threshold, the model correctly predicted 80% of the total presences using only 8% of the study area. The model suggests that the main factor contributing to the expansion of Carpobrotus edulis has been the abandonment of agriculture in the study area. In addition, proximity to the shoreline and above-average erosion potential in the study area both seem to benefit the plant’s expansion. Conversely, steeper and longer slopes, and greater distances from the shoreline, were found to be significant contributors to the plant’s absence.