POSITIVE RELATIONSHIPS BETWEEN HUMAN IMPACT AND BIODIVERSITY: THE CASE OF THE FIRE-BELLIED TOAD (BOMBINA BOMBINA) IN EUROPE

Abstract

Habitat modification affects amphibians indirectly by reducing energy reserves and energy allocated to growth and reproduction, and by affecting population dynamics and viability. Marginal populations of amphibians in Latvia and Ukraine are particularly vulnerable. On the other hand, several studies have shown a positive relationship between human density and biodiversity, indicating that species-rich areas and human enterprises quite often co-occur. Therefore, both positive and negative correlations between human population and species richness may be expected. For a better understanding of what constitutes suitable habitat we used a habitat modeling approach, where modeling can be used for revealing species ecological requirements and relationships between the distribution of species and predictive variables, as well as the importance of each variable in model building. Here we employed maximum entropy (MaxEnt) niche modeling, as a tool to assess potential habitat suitability (HS) for amphibians in Europe, making special emphasis on anthropogenic impact. We used 2474 georeferenced point data (783 - B. bombina occurrence, and to compare results 1691 - L. vulgaris), including results of our field investigations in Latvia and Ukraine. The predictor variables used for modelling the toad species HS suitability were of climate derived from the WorldClim database (19 bioclimatic variables). Human impact was assessed by the Human Footprint (HF), produced through an overlay of a number of global data layers that represent the location of various factors presumed to exert an influence on ecosystems: human population distribution, urban areas, roads, navigable rivers, and various agricultural land uses. Using the Spearman rank correlation, a low, however statistically significant positive correlation (p<0.05), was found between the predicted HS and the HF.