The need for IUCN species distribution update - the case from a large threaten ungulate in Southwest China
Guan tianpei1#, Jacob R Owens2, Yang Kong1,Yang Jian1, Gu Xiaodong3, Song yanglin4#
(1. Institute of Qinghai-Tibetan Plateau, Southwest Minzu University, Chengdu 610225,China)
(2. Los Angeles Zoo and Botanical Garden, Los Angeles, CA, 91602, USA)
(3.Sichuan Station of Wildlife survey and Management, Chengdu 610082, China )
(4.Institute of Zoology, Chinese Academy of Sciences, Beijing 100101, China )
# Corresponding to: tp-guan@hotmail.com; songyl@ioz.ac.cn
Abstract: Species distributions are one of the fundamental factors needed for understanding and conserving wildlife. While the IUCN Red List of Threatened Species is the primary applied reference for biodiversity conservation, limitations in data availability and analyses of the distributions of some species may limit accurate threat classification assessments and conservation recommendations. Improving the accuracy of species distributions in light of growing data and analytical methods is a key step to increasing the efficacy of the Red List. In this study, we reassessed the distribution of takin (Budorcas taxicolor tibetana ), a large ungulate in Sichuan Province, southwest China , classified by the IUCN as vulnerable. Using species distribution models and reported habitat requirements, we updated the takin distribution map. Our updated distribution range in the study area (79,449km2) was 61.31% of current distribution range (CDR) on the IUCN red list. This reduction was in large part due to the inclusion in the CDR of substantial areas of lowland plains, high human disturbance, and non-forest habitat, which provide no suitable habitat for takin. According to our results, suitable takin habitat covered 18.97% of the CDR, suggesting a substantially over-estimated distribution. However, there are high proportions of habitat (40%) still covered by the nature reserve network, indicating the importance of protected areas (PAs) in conservation threaten species. We recommend that experts apply the basic approach presented herein to update the Red List distributions for more species to increase the accuracy of assessments and resulting conservation applications.
Key words: Red list, geographic distribution, Giant panda, Protected Area,
The distribution of a given species is the result of long-term interactions with natural processes (Morris 2003) and both short—and long-term anthropogenic impacts (Stabach et al., 2016). Numerous species are threatened due to habitat loss and population decline caused by anthropogenic changes across the global landscape and the over-exploitation of natural resources (Moyle & Williams, 2010; Sánchez-Bayo & Wyckhuys,2019). Therefore, spatial distributions are one of the very basic characteristics needed to understand the natural history and ecology of any given species (Grenyer et al., 2006). They are also dynamic, influenced by fluctuations in environmental conditions, including climate (Perry et al.,2005), population growth over time (Dou et al., 2013), and human disturbances (Moreno-Rueda & Pizarro, 2007; He et al., 2019). Thus, contemporary knowledge of the dynamics of a species’ distribution is a key indicator of their conservation status, and critical to achieving desired outcomes (Liu et al.,2020) and guiding resource use for conservation actions regionally (Li et al., 2013; Myers et al., 2000). Unfortunately, species with limited data on their population and distributions are still common (IUCN 2020), reducing the accuracy and reliability of their respective conservation status assessments (Beresford et al., 2011, Syfert et al., 2014).
The International Union for Conservation of Nature (IUCN) Red List Categories are internationally recognized as the standard for assessing the extinction risk of species (Butchartet al. 2005; Mace et al. 2008). One of the five standard assessment criteria in the Red List, which determines the “Threatened Category” (e.g. critically endangered, endangered, vulnerable, etc.), is the geographic range of the species based on their extent of occurrence (EOO) and/or area of occupancy (AOO) (IUCN 2019). EOO are estimated by minimum convex polygons (MCP) with well sampled locations (Ramesh et al., 2017), providing the total area the species may be present, including unsuitable or disjunct (unoccupied) areas. AOO are a closer reflection of the actual habitat used by the species because they are based on suitability models or occupancy data within the EOO. Not all threaten species are well sampled throughout their potential range, and their geographic distribution delineated by MCP may differ significantly from reality, providing a clear opportunity to improve our conservation assessments and actions for those species (Pena et al., 2014). Therefore, potential improvements to these data limitations and species distributions should be a priority for species assessments, particularly in developing countries and species lacking sufficient research.
The takin (Budorcase tibetanus ) is a rare species of ungulate found only in Asia, distribute along the south and east edge of Qinghai-Tibetan plateau, including India, Myanmar and Bhutan. Due to poaching, deforest and habitat isolation, takin are considered as vulnerable by IUCN and listed in appendix II of Red list(Guan et al.,2013), top level of national protected wildlife of China (Jiang et al.,2016). Due to its massive body size and group-living behavior, takin were once the most frequently poached mammal within its range, leading to drastic declines in their populations and distribution in the last century (Wu et al.,1990). There are currently four takin subspecies recognized, including the Sichuan takin (B. t. tibetana ) the most widely distributed and abundant takin subspecies (Zeng et al., 2003) found in primarily in Sichuan Province, with minor portions of their range extending into Gansu Provinces (Guan et al., 2015). Data on their population size and distribution range is limited, restricting the accuracy of threat assessments and conservation actions, including effective habitat management.
Review of recent studies on takin and the diversity and distribution of large ungulates in Sichuan Province (Ge et al., 2011; Guan et al. 2013; Guan et al., 2015; Hu et al., 2018; Hu et al., 2019; Chen et al., 2019) indicated that the actual distribution of Sichuan takin should be much smaller than indicated on the IUCN Red List, due to basic known environmental limits for the species (e.g. elevation, distance to human disturbance, etc.). Thus, an update of their geographic distribution is essential. Furthermore, the Sichuan takin is sympatric with the giant panda (Ailuropoda melanoleuca ), a flagship species of global wildlife conservation. Serving as an umbrella species, giant pandas benefit from numerous protected areas (PAs) across their range, within which extensive measures are taken to protect and restore habitat and connectivity (Wang et al.,2021). In addition to updating the distribution of Sichuan takin to be more accurate, conservation planning and recovery efforts would be bolstered by determining the ratio of takin habitat under protection by giant panda nature reserves or other PAs (Guan et al, 2015; Zhang et al., 2020).
In this study we had two primary objectives. First, we sought to update the distribution of Sichuan takin, from an EOO to AOO, providing new data necessary to more accurately assess their IUCN threat classification and plan conservation efforts. Second, we compared the results of our distribution, estimated via an ecological modeling method based on basic habitat requirement data, to the current distribution range (CDR) based on an MCP, to demonstrate the vast discrepancies between these assessments. Our goal is to both directly improve the conservation of Sichuan takin and encourage the broader conservation community to re-examine our standards for estimating species distributions.