Protected areas (PAs), as cornerstones of biodiversity conservation, are designed to protect representative natural landscapes, ensure the persistence of biodiversity and key ecosystem processes, and provide refuges for native species (Rodrigues et al. 2004; Foxcroft et al. 2010, 2013). However, in recent decades, factors such as the growing international and domestic trade driven by global economic integration, advanced modern transportation, the booming tourism industry, and climate change have enhanced the ability of alien species to overcome geographical barriers, making biological invasions a major global issue for ecological and biological security (Butchart et al. 2010; Wei et al. 2023). Invasive alien plants (IAPs) have become a major threat when seeking to manage PAs (Pyšek et al. 2013; Foxcroft et al. 2017; Moodley et al. 2020). According to a report by the Global Invasive Species Programme (GISP), 487 PAs worldwide face biodiversity challenges posed by IAPs (De Poorter et al. 2007). Even at high-altitude and in arid regions, the problem still exists (Milton and Dean 2010; Alexander et al. 2016). One of the primary objectives of establishing PAs is to conserve biodiversity. However, if large-scale biological invasions occur within PAs, the resulting biodiversity loss could be more severe than in non-PAs. This outcome would directly contradict our original purpose of establishing PAs (Foxcroft et al. 2013).
Since 1980, global records of alien species have increased by 40%, with nearly one-fifth of the earth's surface now at risk of biological invasion (IPBES 2019). About 10% of species on the IUCN Red List of Threatened Species are affected by alien invasions (IUCN 2022). Once noxious IAPs have successfully established dominance in a new habitat, the result may be the breakdown of ecosystem function and increased biodiversity loss (Ju et al. 2012). Climate is considered a major environmental factor influencing species distribution (Xiong et al. 2019; Li et al. 2020). Under the background of climate change, invasions by alien plants may intensify (Robinson et al. 2020). Research suggests that climate change, for example the intensity and duration of extreme events (heat waves, heavy rainfall, wildfires, droughts, and hurricanes), may actively facilitate invasions by alien plants and ultimately compromise biodiversity protection within PAs (White et al. 2001; Fargione et al. 2003; Hannah et al. 2007; Pereira et al. 2010; Diez et al. 2012; Hou et al. 2014; Early et al. 2016; Grenz and Clements 2023), potentially accelerating the risk of extinction for up to one in six species (Bellard et al. 2012, 2016; Urban 2015). It has been claimed that future climate change will both increase and reduce invasions (Seebens et al. 2015; Ziska et al. 2019; Clements et al. 2022; Qin et al. 2024). These contrasting responses imply that some invasive alien plants may expand their ranges under future climate scenarios, while others may contract. Given the variation in geographic location and species composition among NRs, the changes in invasion risks they face under future climate scenarios remain uncertain. Therefore, when discussing the issue of invasion in NRs, it is necessarily essential to consider the impact of climate change.
Global species and ecosystem diversity are declining at an unprecedented rate (Butchart et al. 2010). Biological invasions and climate change are two major driving forces (Walther et al. 2009; Jaureguiberry et al. 2022). Particularly in China, rapid economic development has promoted the international exchange of goods and people, and IAPs have increased rapidly (Li and Ma 2010). Currently, China may face an even more severe situation in terms of biological damage than most other countries (Yang 2008; Paini et al. 2016). Historically, China has introduced nonnative species that afford significant economic benefits (Li et al. 2015; Lin et al. 2022; Hao and Ma 2023). Geographically, the terrain and climate of China are very diverse (Mittermeier and Goettsch Mittermeier 2005). Thus, the country contains many habitats suitable for IAPs if invasion is successful (Yu et al. 2020; Yu and Chen 2020; Qin et al. 2024). Rapid economic development, accompanied by explosive growth in international trade and transportation, has heightened the risk of alien species invasions (Li and Ma 2010; Ju et al. 2012; Yu et al. 2020; Yu and Chen 2020). What’s more, the damage caused by an invasion lags the invasion per se (Mooney and Cleland 2001; Gallardo et al. 2017). Thus, the situation in China is likely to become even more challenging in the future (Kelly et al. 2021; Robeck et al. 2024).
According to an available data, the direct economic loss caused by 283 invasive species in China has exceeded USD 2397.39 million annually, of which 66.4% is attributable to IAPs (Xu et al. 2006; Ding et al. 2015). To date, more than 400 IAPs have been recorded in China (Yan et al. 2020b; Lin et al. 2022; Qin et al. 2024). Many studies have described IAP compositions, distributions, and potential areas of invasion (Yan et al. 2020b; Lin et al. 2022; Qin et al. 2024). In terms of researches on distribution pattern, previous studies have focused primarily on between-province differences in IAP distribution patterns or only assessed the risks to a few NNRs (Pan et al. 2015; Gong et al. 2017; Chen et al. 2021a, b, 2022; Zhao et al. 2022). Thus, invasive risks to the whole nature reserve (NR) network still remain unknown (Gong et al. 2017; Wang et al. 2020b; Zhao et al. 2022). The regional specificities of NRs in terms of both species composition and population dynamics have been overlooked, so the information available is too general to aid the practical management of NRs (Chen et al. 2021b, 2022; Hao and Ma 2023; Qin et al. 2024). Nonetheless, they have been valuable in terms of the research frameworks chosen and the data collected, shedding new light on the risk that IAPs pose to NRs.
It is estimated that the minimum economic cost of biological invasions between 1970 and 2017 amounted to USD 1.288 trillion (Diagne et al. 2021). Among all measures for managing alien species invasions, early monitoring and rapid response are the most cost-effective approaches. Specifically, every dollar spent on prevention can save USD 17 in long-term costs (MISAC, 2016). Therefore, assessing the current status and distribution patterns of IAPs in China's NRs, as well as predicting future invasion dynamics under climate change, is of paramount importance for the management and construction of NRs and for biodiversity conservation in China. In this study, we focused on the risks posed by IAPs to NNRs and PNRs. We documented > 120,000 IAP occurrences and used several algorithms to analyze the current and possible future distribution patterns. We present the IAP distribution patterns in the NR network and the key factors driving these patterns, the potential IAP distribution patterns in the NR network under multiple climate scenarios, the invasive risks posed by IAPs to the NR network, and countermeasures that may prevent IAP invasion and mitigate NR biodiversity loss.