Soil erosion is a major issue, causing the loss of topsoil and fertility in agricultural land in mountainous terrain. Estimation of soil erosion in Nepal is essential because of its agriculture-dependent economy (contributing 36% to national GDP) and for preparing erosion control plans. The present study, for the first time, attempts to estimate the soil loss of Nepal through the application of the Revised Universal Soil Loss Equation (RUSLE) model. In addition, it analyzes the effect of Land Use and Land Cover (LULC) and slope ( $\mathsf{\beta })$ exposition on soil erosion. Nation-wide mean annual soil loss of Nepal is estimated at 25 t ha⁻¹ yr⁻¹ with a total of 369 million tonnes (mT) of potential soil loss. Soil erosion based on the physiographic region of the country shows that the Middle Mountains, High Mountains, High Himal, Chure, and Terai have mean erosion rates of 38.0, 32.0, 28.0, 7.0, and 0.1 t ha⁻¹ yr⁻¹. The soil erosion rate by basins showed that the annual erosions of the Karnali, Gandaki, Koshi, and Mahakali River basins are 135, 96, 79, and 15 mT, respectively. The mean soil erosion rate was significantly high (34 t ha⁻¹ yr⁻¹) for steep slopes (β > 26.8%) and the low (3 t ha⁻¹ yr⁻¹) for gentle slopes (β < 5%). Based on LULC, the mean erosion rate for barren land was the highest (40 t ha⁻¹ yr⁻¹), followed by agricultural land (29 t ha⁻¹ yr⁻¹), shrubland (25 t ha⁻¹ yr⁻¹), grassland (23 t ha⁻¹ yr⁻¹), and forests (22 t ha⁻¹ yr⁻¹). The entire area had been categorized into 6 erosion classes based on the erosion severity, and 11% of the area was found to be under a very severe erosion risk (> 80 t ha⁻¹ yr⁻¹) that urgently required reducing the risk of erosion.

Studies on recent climate trends from the Himalayan range are limited, and even completely absent at high elevation (> 5000 m a.s.l.). This study specifically explores the southern slopes of Mt. Everest, analyzing the time series of temperature and precipitation reconstructed from seven stations located between 2660 and 5600 m a.s.l. during 1994–2013, complemented with the data from all existing ground weather stations located on both sides of the mountain range (Koshi Basin) over the same period. Overall we find that the main and most significant increase in temperature is concentrated outside of the monsoon period. Above 5000 m a.s.l. the increasing trend in the time series of minimum temperature (+0.072 °C yr−1) is much stronger than of maximum temperature (+0.009 °C yr−1), while the mean temperature increased by +0.044 °C yr−1. Moreover, we note a substantial liquid precipitation weakening (−9.3 mm yr−1) during the monsoon season. The annual rate of decrease in precipitation at higher elevations is similar to the one at lower elevations on the southern side of the Koshi Basin, but the drier conditions of this remote environment make the fractional loss much more consistent (−47% during the monsoon period). Our results challenge the assumptions on whether temperature or precipitation is the main driver of recent glacier mass changes in the region. The main implications are the following: (1) the negative mass balances of glaciers observed in this region can be more ascribed to a decrease in accumulation (snowfall) than to an increase in surface melting; (2) the melting has only been favoured during winter and spring months and close to the glaciers terminus; (3) a decrease in the probability of snowfall (−10%) has made a significant impact only at glacier ablation zone, but the magnitude of this decrease is distinctly lower than the observed decrease in precipitation; (4) the decrease in accumulation could have caused the observed decrease in glacier flow velocity and the current stagnation of glacier termini, which in turn could have produced more melting under the debris glacier cover, leading to the formation of numerous supraglacial and proglacial lakes that have characterized the region in the last decades.

This contribution examines glacier changes on the south side of Mt. Everest from 1962 to 2011 considering five intermediate periods using optical satellite imagery. The investigated glaciers cover ~ 400 km2 and present among the largest debris coverage (32%) and the highest elevations (5720 m) of the world. We found an overall surface area loss of 13.0 ± 3.1% (median 0.42 ± 0.06 % a−1), an upward shift of 182 ± 22 m (3.7 ± 0.5 m a−1) in snow-line altitude (SLA), a terminus retreat of 403 ± 9 m (median 6.1 ± 0.2 m a−1), and an increase of 17.6 ± 3.1% (median 0.20 ± 0.06% a−1) in debris coverage between 1962 and 2011. The recession process of glaciers has been relentlessly continuous over the past 50 years. Moreover, we observed that (i) glaciers that have increased the debris coverage have experienced a reduced termini retreat (r = 0.87, p < 0.001). Furthermore, more negative mass balances (i.e., upward shift of SLA) induce increases of debris coverage (r = 0.79, p < 0.001); (ii) since early 1990s, we observed a slight but statistically insignificant acceleration of the surface area loss (0.35 ± 0.13% a−1 in 1962–1992 vs 0.43 ± 0.25% a−1 in 1992–2011), but an significant upward shift of SLA which increased almost three times (2.2 ± 0.8 m a−1 in 1962–1992 vs 6.1 ± 1.4 m a−1 in 1992–2011). However, the accelerated shrinkage in recent decades (both in terms of surface area loss and SLA shift) has only significantly affected glaciers with the largest sizes (> 10 km2), presenting accumulation zones at higher elevations (r = 0.61, p < 0.001) and along the preferable south–north direction of the monsoons. Moreover, the largest glaciers present median upward shifts of the SLA (220 m) that are nearly double than that of the smallest (119 m); this finding leads to a hypothesis that Mt. Everest glaciers are shrinking, not only due to warming temperatures, but also as a result of weakening Asian monsoons registered over the last few decades. We conclude that the shrinkage of the glaciers in south of Mt. Everest is less than that of others in the western and eastern Himalaya and southern and eastern Tibetan Plateau. Their position in higher elevations have likely reduced the impact of warming on these glaciers, but have not been excluded from a relentlessly continuous and slow recession process over the past 50 years.

Himalayan glaciers, in general, are shrinking and glacial lakes are evolving and growing rapidly in number and size as a result of climate change. This study presents the latest remote sensing-based inventory (2017) of glacial lakes (size ≥0.0036 km2) across the Nepal Himalaya using optical satellite data. Furthermore, this study traces the decadal glacial lake dynamics from 1977 to 2017 in the Nepal Himalaya. The decadal mapping of glacial lakes (both glacial-fed and nonglacial-fed) across the Nepal Himalaya reveals an increase in the number and area of lakes from 1977 to 2017, with 606 (55.53 ± 16.52 km2), 1137 (64.56 ± 11.64 km2), 1228 (68.87 ± 12.18 km2), 1489 (74.2 ± 14.22 km2), and 1541 (80.95 ± 15.25 km2) glacial lakes being mapped in 1977, 1987, 1997, 2007, and 2017, respectively. Glacial lakes show heterogeneous rates of expansion in different river basins and elevation zones of Nepal, with apparent decadal emergences and disappearances. Overall, the glacial lakes exhibited ~25% expansion of surface areas from 1987 to 2017. For the period from 1987 to 2017, proglacial lakes with ice contact, among others, exhibited the highest incremental changes in terms of number (181%) and surface area (82%). The continuous amplified mass loss of glaciers, as reported in Central Himalaya, is expected to accompany glacial lake expansion in the future, increasing the risk of glacial lake outburst floods (GLOFs). We emphasize that the rapidly increasing glacial lakes in the Nepal Himalaya can pose potential GLOF threats to downstream population and infrastructure.