Ecosystem services research in mountainous regions: A systematic literature review on current knowledge and research gaps.

Mountain ecosystem services (MES) can provide a wide range of benefits for human well-being, including provisioning, regulating, supporting and cultural services. This systematic review work analyzed existed knowledge and research gaps on MES at the global level. The study used databases of science direct, Scopus and google scholar using searching, appraisal, synthesis, and analysis (SALSA) framework. Using specific keywords for the searching engine, the number of publications linked with MES were about 1252 which published between 1992 and June 2019. But, only 74 publications fulfilled the inclusion criteria. The analysis highlighted the existence of gaps in the literature including case studies from a limited geographical areas, focus on regulating and provisioning services, and lack of studies that explore the kinds of interlink between ecosystem services, and occurrence of limitation linked with data and methodology. From the 74 publications used for analysis, only seven of them were addressed mainly trade-offs and synergies, but most of them focus on quantification, qualification and economic valuation of the services. From the total case studies, the services addressed were summed up to 317 services, and the services such as climate regulation, food and fodder, fresh water, recreation and ecotourism, and erosion regulation studied more. On the contrary, photosynthesis, ornamental resources, net primary production, disease regulation, genetic resources, water purification and waste treatments were the least studied. Therefore, future research works should focus on mountainous areas of no and least studied of its ecosystem services. Critical studies are also required that indicate the link between a human being with MES, the trade-offs and synergies between MES and the influence of human beings on the quality and accessibility of ecosystem services. Besides, priority should be given by researches for methodological development and proposing management option for the mountain ecosystem and resource.