Red list of China's forest ecosystems: A conservation assessment and protected area gap analysis

Abstract

Current biodiversity loss is far greater than at any time in human history. As complementary tool to prioritize biodiversity for conservation, the IUCN Red List of Ecosystems (RLE) is well justified as a conservation tool. Although China's biodiversity is among the world's richest, a significant part of this diversity is under threat. Based on the distribution of 229 forest formations, we assessed the risk status according to the IUCN RLE criteria, and evaluated the conservation status of threatened forests by comparing ecosystem distribution with terrestrial national and provincial nature reserves (NNRs and PNRs, respectively). We found that 90 threatened forest formations accounted for 16% of the area, but for 39.3% of the number of assessed formations. Threatened forest formations were mainly located in western Sichuan, Yunnan, southeastern Xizang, southwestern Guangxi, Hainan Island, northeastern China, and the mountains of Taiwan. Tropical rain forests and evergreen broad-leaved forests together accounted for the highest number of threatened formations. Northern Xinjiang (with the Tianshan and Altai Mountains) proved to be a unique area that has rarely been identified as hotspot of plant conservation. On average, NNRs covered 13.2%, and NNRs and PNRs together covered 22.7%, of the threatened forest distribution areas. However, 15 threatened forest formations were not covered by NNRs or PNRs. We suggest that the red list of ecosystems will contribute towards providing a more informative picture of the status of biodiversity. Our work highlights the need to use the red list of ecosystems as additional tool in plant conservation.

Introduction

Biodiversity and ecosystem services are vital to people and nature's health (Díaz et al., 2019). However, the current rate of biodiversity loss is far greater than the background rate, and typically faster than at any time in human history (Díaz et al., 2019; Mace et al., 2018). Global conservation actions have been successful in preventing the extinction of some species (Butchart et al., 2012; Gaston et al., 2008; Jones et al., 2016). However, conservation resources are limited given the increasing number of species under threat. The International Union for Conservation of Nature (IUCN) Red List of Threatened Species is intended to raise awareness of loss of species, and is often used to allocate scarce conservation resources (Mace et al., 2008). In reality, red lists of species might have limitations in setting conservation priorities (Possingham et al., 2002). New tools are therefore needed to add information to conservation strategies.

As complementary method to identify and prioritize ecosystems in need of protection, the IUCN Red List of Ecosystems (RLE) is a justified conservation tool (Keith et al., 2015). Addressing ecosystems has long been a well established imperative in conservation planning (Noss, 1996). Firstly, by assessing the conservation status of ecosystems and ecological communities, the RLE could focus on levels of ecological complexity, such as ecological processes, species interactions and abiotic components of ecosystems, which are poorly covered by the red list of species (Boitani et al., 2015). Secondly, common species are fundamental to ecosystem structure and function (Gaston and Fuller, 2008). However, many previously common species have suffered substantial population declines (Elliott et al., 2010; Lindenmayer et al., 2011). Thirdly, the value of ecosystem services has been very useful in explaining the importance of biodiversity conservation to people (Costanza et al., 2017).

The practice of ecosystem assessment can be traced to the early national and regional listings of ecosystems, communities and habitats in conservation planning efforts (Nicholson et al., 2009). However, their protocols varied widely in concept, threshold values, time frame and spatial scale, leading to inconsistent assessments of threat status (Nicholson et al., 2009). The World Conservation Congress provided resolutions for these problems by initiating development of quantitative criteria for assessing ecosystems (Rodríguez et al., 2011). After substantial expansion of scientific foundations, the updated protocol of the red list of ecosystems was endorsed by the IUCN as global standard for assessment of the threat status of ecosystems (Keith et al., 2015; Keith et al., 2013; Rodriguez et al., 2015).

China is among the world's countries most rich in biodiversity (Lópezpujol et al., 2006; Tang et al., 2006; Wang et al., 2011). Nevertheless, a significant part of this diversity is currently under threat, due partly to overexploitation (Li and Wilcove, 2005; Liu et al., 2016), land use change (He et al., 2014) as well as pollution (Liu, 2013). Studying threatened ecosystems in China, therefore, benefits biodiversity conservation worldwide. Indeed, a recent global analysis of changes in land cover showed that China experienced a major loss of natural area (forest, shrubland and grassland) between 1992 and 2015, ranking third after North America and Europe (van Vliet, 2019). The crucial way to curb such threats to biodiversity is establishing protected areas (Juffe-Bignoli et al., 2014). By the end of 2014, China had established 2729 nature reserves, spanning 15% of its land surface (Xu et al., 2017). Of these 2729, 428 are national nature reserves, encompassing 9.9% of China's land surface. Based on the vegetation map of China, Wu et al. (2011) found that forests were least covered by nature reserves, implying the need of nationwide ecosystem assessment.

Recently, a study in southwestern China showed that 33.3% of ecosystems in this region were threatened (Tan et al., 2017). Nationwide analysis showed that China's nature reserves were not in a strong enough position to provide threatened species with habitat and key ecosystem services (Xu et al., 2017). Specifically, a review of the available literature revealed the major consequences of forest fragmentation throughout China on biodiversity conservation (Liu et al., 2019). To date, no comprehensive studies have been undertaken to evaluate the risks to and conservation status of forest ecosystems in China.

In this study, we present the first nationwide risk assessment of forest ecosystems and evaluate the conservation status of threatened forest ecosystems in China. We defined assessment units as vegetation formations in the Vegetation Map of the People's Republic of China (1:1000000) (Editorial Board of the Vegetation Atlas of China, 2009). In the vegetation classification system of China, the concept and definition of formations is widely accepted, with each formation representing a dominant species of vegetation in its suitable environment (Guo et al., 2018). The spatial distribution of vegetation formations enables us to identify the risk status of each forest formation according to the IUCN Red List of Ecosystems' Categories and Criteria (Bland et al., 2016; Rodriguez et al., 2015). Lastly, we evaluated the conservation status of each threatened forest formation by overlaying the map of nature reserves with the distribution of threatened forest formations, making it possible to calculate to which extent threatened formations are covered by nature reserves, thus identifying forest conservation gaps in China. Three specific questions were addressed in this study: (1) What is the proportion of forest ecosystems that is threatened? (2) Where were the threatened forest ecosystems located? and (3) To what extent are these threatened forest ecosystems protected by nature reserves in China?