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sur le développement des zones arides et semi-arides

Titre : Rising Temperatures In Hot Regions – How Many Species Would Be Able To Survive ?

Auteur : Ghosh, Sounak

Université de soutenance : United Arab Emirates University

Grade : Master of Science (MS) 2019

Résumé
Temperatures are rising throughout the world but not uniformly. Different latitudes have varying degrees of temperature rise and the most rapid changes are happening in the higher northern latitudes while only minor warming is taking place in the hot tropical regions. It has been widely assumed that the biggest ecological impacts will be seen in the cooler northern latitudes and that the impacts in hot tropical regions will be much smaller. However, if species in hot regions are already close to their thermal limits and if species in cold regions are far below them, it may be that small temperature increases in hot regions may be more damaging than large temperature increases in cold regions. Here by compiling data from 726 species published in 278 publications which have measured the Upper Critical Temperatures (CTmax) in a wide range of ectothermic animal species, the distribution of these upper thermal limits were examined and compared with temperatures in hot and cold regions. The results indicate that very few species reach their CTmax below 30°C. The vast majority of species reach their CTmax between 30°C - 50°C. Cold regions are far below the upper critical temperatures of most species whereas the hot regions are nearer or exceeding the upper critical temperatures of many species. The impact of a 3°C temperature increase in hot and in cold regions was estimated. It was found that a 3°C temperature increase in cold regions would result in almost no species being pushed beyond their upper thermal limits. As temperatures reach 30°C, it was found that a 3°C temperature increase could push an appreciable number of species over their upper critical temperature. The magnitude of this impact then increased steadily, being much higher in hot regions. In regions where temperatures are reaching 45°C, a 3°C temperature increase could push the majority of the remaining species over their thermal limits. These results suggest that even though temperature increases in hot regions are much smaller than temperature increases in cold regions, the ecological impacts could be much greater, and many more species could be pushed over their upper thermal limits.

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