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International Institute for Geo-Information Science and Earth Observation (ITC) 2007

Influence of human activities on the distribution of amphibians and reptiles in the Salamanca province, Spain

Yan Sun

Titre : Influence of human activities on the distribution of amphibians and reptiles in the Salamanca province, Spain.

Auteur : Yan Sun

Etablissement de soutenance : University of Twente International Institute for Geo-Information Science and Earth Observation (ITC)

Grade : Master of Science in Geo-Information Science and Earth Observation 2007

Résumé
The population decline of amphibians and reptiles has aroused worldwide attentions during the past decades. Human activities were considered as one of the most important potential factors leading to this problem. For studying the relationship between species distribution and human activities, 4 amphibians ( Pelobates cultripes , Bufo calamita , Hyla arborea , and Pleurodeles waltl ) and 4 reptiles ( Psammodromus algirus , Psammodromus hispanicus , Blanus cinereus , and Timon lepida ) were selected, and 2780 species presence points were obtained in the Salamanca Province of Spain from 2000 to 2002. Statistical frequency method and Bayes’ theorem were applied for finding out the relationship between species presence and human activities influence (represented by human population density). Bayes’ probability theorem could avoid the bias caused by sampling method and showed more reasonable results than frequency method. The results showed that both the amphibians and reptiles prefer comparatively weak human influence, which was most probably because strong human influence could cause the loss of species habitat and the death of the fragile species by accident. However, different species reacted differently along with the change of human influence. For those reptiles, the results showed the species presence decreased with the in crease of human influence, while for those amphibians, the moderate human influence would favour the species presence to some extend. The reason could be in the moderate human influence area, human activities like building ponds and irrigating farmland closed to the villages provided more essential habitats for amphibians, especially for their larva. On the contrary, the growth of reptiles does not rely on water body very much. For the purpose of better studying the species habitat, MAXENT (Maximum Entropy model) was applied for modelling the species distribution, especially considering human activities parameter. The modelling was constructed firstly with only environmental parameters and then with both environmental and human activities parameter for the eight species. The results showed that adding human activities parameter could slightly improve the modelling accuracy for most of species. In addition, the output distribution maps from two models had significant difference. The model added human activities parameter displayed a distribution map with lower habitat probability in human resident places, and more fragmental species habitat than the model with only environmental parameters, which means the former map was better indicating that species avoiding strong human influence. Studying the influence of human activities on species distribution and creating the species distribution maps can not only give a better understanding of human influence to the nature, but also help decision-maker to take proper methods protecting the species.

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Page publiée le 2 février 2018