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The leaf area index (LAI) has been traditionally used as a photosynthetic variable. LAI plays an essential role in forest cover monitoring and has been identified as one of the important climate variables. However, due to challenges in field sampling, complex topography, and availability of cloud-free optical satellite data, LAI assessment on larger scale is still unexplored in the Sikkim Himalayan area. We used two optical instruments, digital hemispherical photography (DHP) and LAI-2200C, to assess the LAI across four different forests following 20 × 20 m 2 elementary sampling units (ESUs) in the Himalayan state of Sikkim, India. The use of Sentinel-2 derived vegetation indices (VIs) demonstrated a better correlation with the DHP based LAI estimates than using LAI-2200C. Further, the combination of both reflectance bands and VIs were integrated to predict the LAI maps using random forest model. The temperate evergreen forests demonstrated the highest LAI value, while the predicted maps exhibited LAI maxima of 3.4. The estimated vs predicted LAI for DHP and LAI-2200C based estimation demonstrated reasonably good (R 2  = 0.63 and R 2  = 0.68, respectively) agreement. Further, improvements on the LAI prediction can be attempted by minimizing errors from the inherent field protocols, optimizing the density of field measurements, and representing heterogeneity. The recent rise of frequent forest fires in Sikkim Himalaya prompts for better understanding of fuel load in terms of surface fuel or canopy fuel that can be linked to LAI. The high-resolution LAI map could serve as input to forest fuel bed characterization, especially in seasonal forests with significant variations in green leaves and litter, thereby offering inputs for forest management in changing climate., (© 2022. The Author(s), under exclusive licence to Springer Nature Switzerland AG.)

Ecotourism is the greener variant of tourism which advocates conservation of biodiversity and acts as a development strategy to build a self-sustainable system to help protect and further enhance the ecosystem through the income generated by ecotourism activities. There is a strong linkage between biodiversity conservation and ecotourism which has also been recognized by the UN and finds its place under the technical note on "Biodiversity and the 2030 Agenda for Sustainable Development". But, are the stakeholders of the ecotourism destinations religiously following practices that will ensure biodiversity conservation at all times is something that needs continuous evaluation and validation. The authors have worked in the past on developing multi-stage methodology (ESA Framework, ESM Model and their validation) using Qualitative and Quantitative techniques and successfully developed Ecotourism Sustainability Assessment Method (ESAM) for such an appraisal. The present paper aims at devising a process which will show the applicability of ESM model in identifying the biodiversity related and other environmental factors, adversely impacting the ecotourism destination at present, or may impact it in times to come. In addition, it also offers the prescription to solve these issues and achieve the goal of ecotourism sustainability at the operational level. This proposed process initially will be defined with the help of a site-level case study of Mt. Kangchendzonga Base Camp Trek, Sikkim. Later, this would be extended to other ecologies and geographies so that in the future, a robust and useful model, applicable for most of the ecotourism destinations, can be developed.