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.