Introduction
Accelerated anthropogenic impacts and fluctuating climate change are widely considered to be responsible for the continuous loss of biodiversity (Dirzo et al., 2014; Koch et al., 2006). Over the past three centuries, many mammals in China have exhibited distinct population declines and shrinking distribution ranges, likely associated with increasing human populations and climate fluctuations (Wan et al., 2019). Habitat loss, population decline or displacement, and even local extinction of wildlife are caused by anthropogenic factors, including overexploitation, agricultural development needs, urbanization, deforestation and human-introduced diseases (Trombulak and Frissell, 2000; Rosser and Mainka, 2002; Hill and Hamer, 2004; Smith et al., 2006; Mckee and Chambers 2011; Dirzoet et al., 2014; Menon et al., 2015; Turvey et al., 2017). Climate change, including warming, cooling and fluctuation, could influence the survival of wildlife regionally, and distribution shifts are the response that would most likely lead to local extinction (Pearson and Dawson, 2003; Koch and Barnosky, 2006; Chen et al., 2011; Hei, 2012; IPCC, 2014; Li et al., 2015). It is widely recognized that human disturbances have the greatest impact on wildlife extinction, but the contribution of climatic factors can reach up to 54% (Urban, 2015; Sahajpal and Goyal, 2018). In addition, the interaction of climate change and human interference could accelerate wildlife extinction (Wan et al., 2019). Therefore, determining which specific factors have a greater impact will influence conservation decisions.
The Chinese pangolin (Manis pentadactyla ) is a unique, scale-covered mammal species that mainly feeds on ants and termites, playing an important role in maintaining the stability of the ecosystem (Sharma et al., 2020; Liu et al., 2020). China used to be one of the largest consumer markets of pangolins and their derivatives in Asia (Sharma et al., 2020). Scales of Chinese pangolin were used in traditional medicine, and its meat was consumed as a luxury food in China. In the past five decades, the distribution range of Chinese pangolins has been rapidly shrinking, and the population has declined by 80%-90% in several provinces of China (Challender et al., 2015, 2019). Severe hunting and poaching stress imposed by the local and international pangolin trade across its distribution range have been demonstrated to cause the accelerated decline of Chinese pangolins during this time period (Nash et al., 2016; D’Cruze et al., 2018). The government of China made positive efforts to protect this endangered species, such as upgrading Chinese pangolins from National Level II Protected Animals to Level I and removing the species from theChinese Pharmacopoeia in 2020, which strengthened the conservation policy (National Forestry and Grassland Administration, 2020). Despite the enormous human influence, we still cannot ignore the negative effects of climate change on the loss and alteration of the Chinese pangolin habitat because climate change during this period was also very drastic. The average global surface temperature increased by approximately 1 °C, and extreme weather events occur more frequently than before (NOAA, 2021).
Identifying the causes of local extinction is an indispensable step in conservation practice (Mateo-Tomás and Olea, 2010). However, the quantitative relationships between local extinctions of Chinese pangolin and anthropogenic and climatic factors have not been evaluated. It is difficult to quantitatively determine which variables are the main factors due to the lack of long-term monitoring data. Local chronicles data provide insight into the roles of human impacts and climate change in causing local extinctions of Chinese pangolins. For more than 3600 years, since the Shang and Zhou dynasties, China has a long history of recording significant political and natural events. Owing to its economic value (mainly for traditional medicine or as a rare gift), unique characteristics and reactions to human activities (curling up when threatened), sightings of Chinese pangolin were likely to be recorded in historical documents. Therefore, local chronicles (from province to district), official and formal records such as Twenty-Four Histories , and Comprehensive Mirror for Aid in Government could be used to track the changes in the distribution of the Chinese pangolin. In addition, the History Database of the Global Environment (HYDE) consists of historical population estimates and land use metrics, in particular, the population count, population density, cropland coverage and the degree of grazing, which are human factors affecting the survival of wild animals. The time coverage of the HYDE database is from 10000 BC to 2016 AD. Data from 1700-2016 have a 10-year resolution, and the spatial resolution reaches 0.5×0.5 arc degrees (approximately 50×50 km2) (Goldewijk et al., 2017). Weather data reconstructed from the records of δ18O in ice cores in the Himalayas and tree rings worldwide exhibit a highly significant correlation with the average temperature and can be used as a metric to assess climate change in the Northern Hemisphere (Zhao et al., 2014; Shi et al., 2015). Benefiting from the unremitting development and updating of historical databases of the global environmental data (anthropic and climatic) and combining local chronicles, we have an opportunity to identify the causes of local extinctions of the Chinese pangolin to inform conservation actions that target the species (Wen 2009).
Therefore, we used local chronicles of the Chinese pangolin in China and combined them with quantified anthropogenic stressors (represented by population counts, population density, cropland coverage and grazing) and temperature variations (represented by holistic temperature and regional temperature) through a generalized additive model (GAM) to determine key causes of local extinctions in 1700-2000 (Wan et al., 2019). Then, we lowered the temporal scale and built an extinction risk model estimated by the maximum entropy algorithm to identify which variables contributed to the extinction events in 1970-2000, relying on much more accurate and detailed environmental data (RoDder et al., 2009; Benito et al., 2009). Through principal component analysis, we further determined the degree of variation of those variables. Finally, we used rescue information from the wildlife rescue departments and Global Biodiversity Information Facility (GBIF) database from 2000-2020 to evaluate the threatened status of extant Chinese pangolin populations in China. Learning from history, our research can have implications for the conservation practices to protect Chinese pangolins in China now and in the future.