The Changing Himalayas Understanding Water Climate and Vegetation in the Third Pole

Abstract

The greater Himalayan region, the roof of the world contains the most expansive and rugged high-elevation areas on Earth, with the largest areas covered by glaciers and permafrost outside of the polar regions. The water resources from this area drain through ten of the largest rivers in Asia, in the basins of which more than 1.3 billion people reside. These mountains play an important role in global atmospheric circulation, biodiversity, and monsoon-fed agriculture, but more importantly, they modulate the climate in Southeast Asia (Azam et al., 2021). The biodiversity and water resources of this region are currently facing threats from a multitude of driving forces. Anthropocene warming has resulted in unpredictable precipitation regimes and accelerated cryospheric melt (Summerhayes and Zalasiewicz, 2018), which has serious implications for downstream water availability in both the short and long term, as up to 50% of the average annual flows in the rivers are contributed by snow and glacial melting. In a similar vein, there has been no pan-Himalayan effort to examine plant ecophysiology and adaptability to the changing environment, particularly in the context of seasonal warming, wetter monsoons, shorter winters and migrating treelines. Most studies in the Himalayan region fall short because of its extreme and complex topography and the lack of adequate gauge data. There is an urgent need to close the knowledge gap by employing an interdisciplinary method to study snow, ice, and water; downscaling climate models; applying hydrological models to predict water availability, and developing basin-wide scenarios which also take water demand and socioeconomic development into account. To address the first point: remoteness and lack of in-situ data, we embarked on an extensive pan-Himalayan survey collecting water, soil and plants from 5 transects spanning the mountain range. The risk and labour associated with such a mammoth task paid off in mapping the water and carbon cycle at a significantly high spatiotemporal