Study of Ecosystem Services Provided by Mountain Watersheds

Abstract

Ecosystem service (ES) mapping has emerged as a robust scientific approach to understanding landscape dynamics, conserving biodiversity, and sustaining nature’s contributions to people amid land-use/land-cover change and accelerating climate change. In ecologically fragile mountain systems such as the Himalaya, ecosystem services are highly sensitive yet rarely quantified for decision making. The Askot landscape, situated in the western Himalayan landscape in Pithoragarh district of Uttarakhand, covers approx. 4496.49 sq.km. Despite providing vital regulating, provisioning, and supporting services, this region has received limited integrated assessment. Addressing this gap, the present study examined long-term land-use–land-cover (LULC) dynamics, associated carbon sequestration trends, and future climate vulnerability to support evidence-based decision making. To achieve this, this study pursued three objectives: (i) to analyse spatial and temporal LULC changes, (ii) to quantify trends in above-ground carbon storage across forest and vegetation types, and (iii) to identify climatically vulnerable areas under future climate scenarios.The results reveal that nearly 10% of the Askot landscape experienced LULC change over the study period, with the most pronounced transformations occurring between 2011 and 2020, indicating an acceleration of recent landscape dynamics. Forests occupy only ~18% of the total landscape, yet they underpin a substantial share of ecosystem services. Dense forest area declined from 391.7 sq.km (1990) to 369.4 sq.km (2020), while moderate dense forest showed a sharper reduction (259.3 to 227.9 sq.km), accompanied by a marked increase in open forest (155.9 to 206.9 sq.km). This pattern reflects widespread forest degradation rather than abrupt deforestation. Scrub ecosystems also declined, while landslides more than doubled (7.45 to 15.8 sq.km), signalling growing geomorphic instability. High-elevation systems exhibited strong climate sensitivity, with alpine meadows shrinking (842.2 to 790.4 sq.km) and snow cover declining by over 100 sq.km, alongside a substantial expansion of the Moraine class (473.3 to 714.5 sq.km), indicating snowline instability and water stress, affecting another vital ES.Vegetation-type analysis further confirms degradation across major forest types. Oak-dominated systems (Quercus leucotrichophora (Banj Oak), Quercus semecarpifolia (Kharsu Oak), Quercus floribunda (Moru Oak), Betula-Abies (Birch–Fir), Deodar, Pine, and Mixed broadleaf forests all showed declines in dense and moderate canopy classes with a concurrent rise in open forest cover. Above-carbon carbon storage and sequestration show consistent declines across oak-dominated forests (Banj, Kharsu, Moru), Birch–Fir, Deodar, Pine, and mixed broadleaf systems, primarily through transitions from dense and moderate canopy classes to open forest. These structural changes directly influenced carbon dynamics. In 1990, the total AGC was estimated at 67,529.41 MgC, which declined to 66,597.79 MgC by 2020. Projections for 2050 indicate a further reduction in AGC to 66,062.30 MgC, corresponding to an additional loss of 535.49 MgC between 2020 and 2050. Total above-ground carbon stock declined from 67,529.41 MgC in 1990 to 66,062.30 MgC by 2050, representing a cumulative loss of 1,467.11 MgC over six decades. Meadows and scrub ecosystems showed the steepest proportional carbon losses, while forest carbon decline was driven largely by canopy thinning rather than loss of forest area. The relatively lower projected future carbon loss reflects the slow-changing nature of forest types, even as degradation continues.Oak forests emerge as the primary climate mitigation asset in the Askot landscape, contributing ~61% of total above-ground carbon (AGC) by 2050 despite occupying less than 10% of the total area. When combined, all forest classes (oak, temperate, and mixed forests) account for 18% of total area and contributing to approximately 85% of total AGC, clearly establishing forests as the dominant carbon pool within the watershed. This concentration of carbon within a limited forested area highlights the disproportionate importance of forests. Even marginal losses in forest cover translate into substantial carbon emissions; for instance, a 0.26% reduction in oak forest area corresponds to an estimated loss of ~105 MgC.The scope of present study was to identify climatically vulnerable ecosystems in the Askot landscape by integrating Climate-Ecological Niche Factor Analysis (CENFA). To perform this analysis, two Shared-Socioeconomic Pathways (SSP) were considered, SSP245 (Middle of the road) and SSP585 (Worst-case scenario) for mid-century (2041-2060) and end-of century (2081-2100). Climate vulnerability assessment using CENFA highlights extensive areas of medium to high vulnerability, particularly under SSP585. High-vulnerability zones increase from 1266.7 sq.km (SSP245) to 1535.2 sq.km (SSP585) in the near future, and further expand to 1762.6 sq.km by end-century, disproportionately affecting alpine, sub-alpine, and degraded forest regions. These areas spatially correlated with zones of observed LULC change and carbon decline, underscoring climate–LULC risks. Askot landscape is undergoing progressive ecological degradation driven by forest structural decline, high-elevation climate stress, and increasing disturbance. Integrating LULC dynamics, carbon assessment, and CENFA this research can support ecosystem-based adaptation leading to climate-adaptive land-use planning.