A critique of the Right of Passage as a guide to elephant corridors in India

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The Asian elephant (Elephas maximus L.), an endangered species, has been exterminated across most of its range over the past few centuries (De Silva et al., 2023), and now survives in small, fragmented populations (Leimgruber et al., 2003). Reconnecting elephant habitats is a major challenge for the long-term survival of this species (Davidar et al., 2023). A report on elephant corridors in India "The Right of Passage—elephant corridors in India" or ROP (Menon et al., 2005) identifies 88 corridors throughout the Indian territory for conservation purposes. This document was published by the Wildlife Trust of India and financially supported by a grant from the US Fish and Wildlife Services. By the ROP authors' own admission, their work was preliminary and their list incomplete. In several instances, this warning has been ignored and projects were approved (Dutt, 2015) or encouraged (Bagla, 2009) on the basis that no corridor occurred in the ROP for the sites' locations. Even when other endangered species were concerned, focus remained on the elephant or absence thereof in the ROP (Bagla, 2009; Davidar, 2009). Due to its importance for policy and public affairs, it is crucial that scientists, decision-makers, and citizens understand the usefulness and the shortcomings of the ROP. The ROP is useful as it attempts to list elephant corridors throughout India. However, it does not have its own working definition for "corridor." In empirical science, no less than in mathematics, definitions are cornerstones of proper reasoning. Without a working definition, there is no possibility of establishing criteria that would help differentiate an elephant corridor from other pieces of land. Furthermore, the absence of such criteria may overlook areas that should be declared corridors. The ROP is at best a compilation of expert opinions with little coordination, together with a few corridors that were validated using movement data and dung pile counts. The methodology for these validation exercises is also missing. The ROP consequently does not qualify as a rigorous scientific study. The ROP has missed critical existing and prior elephant corridors, and mostly identifies short linear paths mostly between reserves, as corridors. In the Nilgiri Biosphere Reserve, which hosts part of the largest Asian elephant population in the world, an evaluation of elephant corridors (Puyravaud et al., 2016) with the factorial least-cost path (Cushman et al., 2009) and resistant kernel techniques (Compton et al., 2007), highlighted that only half of the corridors identified by the ROP were supported by comprehensive and consistent analyses. Only two corridors were common to the ROP and an earlier study in the NBR (Davidar, 1981), which illustrates the limitation of expert knowledge. Expert opinion also tended to ignore the hierarchical nature of corridor networks. Some corridors are more important than others. The Sigur corridor for example, is part of an extended corridor connecting the elephant populations of the Western and the Eastern Ghats. It was not listed in the ROP, even though its importance was highlighted by Puyravaud et al. (2016). The ROP also fails to mention the potential corridor of the Palghat Gap, a paleo-valley between the northern and the southern Western Ghats where elephant population connectivity had been severed only a few generations ago (De et al., 2021), possibly due to agricultural expansion. The second version of the Right of Passage (Menon et al., 2017) identified 101 corridors with no clarification or improvement in the methodology. The authors ignored that between 2000 and 2017, the number of publications in landscape ecology had exploded with technical advances to identify corridors such as the least-cost path modeling (Adriaensen et al., 2003), factorial least cost path modeling (Cushman et al., 2009), resistant kernel methods (Compton et al., 2007), circuit theory (McRae & Beier, 2007), landscape genetics (Cushman et al., 2006; Manel et al., 2003) or species distribution modeling (e.g., Phillips et al., 2004). These techniques could have brought a synoptic and more objective view of connectivity in an updated analysis of elephant corridors. No reference to the Sigur corridor was given either, even though the administration recommended its protection as early as 2009 and even though its importance was confirmed (Puyravaud et al., 2016). Moreover, the opposition to the protection of this corridor raged for more than a decade, on the grounds that it was not listed in the ROP, but fortunately the Supreme Court upheld the increased protection measures by the Tamil Nadu administration (Puyravaud & Davidar, 2022). Due to these methodological shortcomings, outdated comprehension of landscape connectivity and questionable choices made by the editors of ROP, the corridors listed therein need to be verified further using appropriate methods. It follows that it would be contrary to conservation ethics to decide that a corridor does not exist or that an area does not deserve the protection it enjoys based on the ROP. To improve on the ROP, it is imperative to adopt modeling methods that are less prone to personal choice (Zeller et al., 2012). There are excellent recent examples that use powerful modeling methods on movement, genetic and occurrence data to map and prioritize corridors for wildlife species across their ranges, such as for lions (e.g., Cushman et al., 2018) and clouded leopards (e.g., Haidir et al., 2021). We urge the scientific community to follow these examples and conduct nation-wide, consistent mapping of elephant corridors based on rigorous empirical data and robust connectivity modeling methods. India has a remarkable track record in conservation as shown by its large protected area network, effective tiger conservation, and ambitious projects such as the reintroduction of the Cheetah. The effort made by the Ministry of Environment, Forest and Climate Change of India to identify and protect elephant corridors comes from a long tradition of proactive protected area management. In its present form, however, the ROP, for the above reasons, is inadequate as a reference document for elephant corridors in India. The authors declare no conflicts of interest.

Ce résumé expose les affirmations des auteurs. BNTIC ne l’interprète pas comme une validation indépendante des résultats.