This book explores the ecological aspects of climate change. The book is based on theoretical analyses, laboratory studies and field activities which took place between 2009 and 2022. The effects of climate change are analysed using the ecological footprint model and its associated calculation systems. Practical applications in the area of the Danube River are presented and analysed, and interesting and useful data are obtained from Abisko Research Station, 250 kilometres north of the Polar Circle. The book will be of interest to students, PhD candidates, teachers and scientists.