1. Climate Change and Dynamics of Glaciers and Vegetation in the Himalaya: An Overview

Mountains are globally significant as ‘water towers’ of the Earth, as core areas of biodiversity and as source regions for important natural resources and ecosystem services. The ecological integrity of mountain environments is increasingly threatened by global environmental changes including climate change to which physical and ecological systems in mountains are highly vulnerable. Global warming rates have been higher in mountain regions compared to the global mean and have strongly affected the cryosphere, mountain biota and ecosystem processes.

Temperature trends in most Himalayan regions substantially exceed the global mean trend of 0.85 °C between 1880 and 2012, with winter season temperature trends being generally higher than those of other seasons. Precipitation patterns are spatio-temporally differentiated, but show rather decreasing than increasing trends, in particular during summer. On average, glacier mass budgets have been negative for the past five decades, with glaciers in the Himalaya and in the Hindu Kush showing distinct mass losses, while those in the Karakoram are close to balance. Shrinking rates are regionally variable, but often accelerating, corresponding approximately to a W-E gradient of increasing glacier retreat. Biotic responses to current climate change include elevational range shifts of species, intense recruitment of tree species in treeline ecotones and shifts in phenology, resulting in modified structure, composition and functioning of Himalayan ecosystems.