Pastoralism in the highest peaks: Role of the traditional grazing systems in maintaining biodiversity and ecosystem function in the alpine Himalaya

RESEARCH ARTICLE Pastoralism in the highest peaks: Role of the traditional grazing systems in maintaining biodiversity and ecosystem function in the alpine Himalaya Tenzing IngtyID* Department of Biology, University of Massachusetts, Boston, Massachusetts, United States of America * tenzingingty@gmail.com Abstract Rangelands cover around half of the planet’s land mass and provide vital ecosystem ser- vices to over a quarter of humanity. The Himalayan rangelands, part of a global biodiversity hotspot is among the most threatened regions in the world. In rangelands of many develop- ing nations policies banning grazing in protected areas is common practice. In 1998, the Indian state of Sikkim, in the Eastern Himalaya, enacted a grazing ban in response to grow- ing anthropogenic pressure in pastures and forests that was presumably leading to degra- dation of biodiversity. Studies from the region demonstrate the grazing ban has had some beneficial results in the form of increased carbon stocks and regeneration of some species of conservation value but the ban also resulted in negative outcomes such as reduced household incomes, increase in monocultures in lowlands, decreased manure production in a state that exclusively practices organic farming, spread of gregarious species, and a per- ceived increase in human wildlife conflict. This paper explores the impact of the traditional pastoral system on high elevation plant species in Lachen valley, one of the few regions of Sikkim where the grazing ban was not implemented. Experimental plots were laid in along

an elevation gradient in grazed and ungrazed areas. Ungrazed areas are part of pastures that have been fenced off (preventing grazing) for over a decade and used by the locals for hay formation. I quantified plant species diversity (Species richness, Shannon index, Simp- son diversity index, and Pielou evenness index) and ecosystem function (above ground net primary productivity ANPP). The difference method using movable exlosure cages was used in grazing areas to account for plant ANPP eaten and regrowth between grazing peri- ods). The results demonstrate that grazing significantly contributes to greater plant species diversity (Species richness, Shannon index, Simpson diversity index, and Pielou evenness index) and ecosystem function (using above ground net primary productivity as an indica- tor). The multidimensional scaling and ANOSIM (Analysis of Similarities) pointed to signifi- cant differences in plant species assemblages in grazed and ungrazed areas. Further, ecosystem function is controlled by grazing, rainfall and elevation. Thus, the traditional transhumant pastoral system may enhance biodiversity and ecosystem function. I argue that a complete restriction of open grazing meet neither conservation nor socioeconomic PLOS ONE PLOS ONE | https://doi.org/10.1371/journal.pone.0245221 January 7, 2021 1 / 19 a1111111111 a1111111111 a1111111111 a1111111111 a1111111111 OPEN ACCESS Citation: Ingty T (2021) Pastoralism in the highest peaks: Role of the traditional grazing systems in maintaining biodiversity and ecosystem function in

the alpine Himalaya. PLoS ONE 16(1): e0245221. https://doi.org/10.1371/journal.pone.0245221 Editor: Bhoj Kumar Acharya, Sikkim University, INDIA Received: August 12, 2020 Accepted: December 23, 2020 Published: January 7, 2021 Peer Review History: PLOS recognizes the benefits of transparency in the peer review process; therefore, we enable the publication of all of the content of peer review and author responses alongside final, published articles. The editorial history of this article is available here: https://doi.org/10.1371/journal.pone.0245221 Copyright: © 2021 Tenzing Ingty. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Data Availability Statement: All relevant data are within the manuscript and its Supporting information files. Funding: Field work was supported by funding from 1. Department of Biotechnology, Ministry of