Introduction

The Hainan tropical rainforest, located on Hainan Island in China, represents a globally significant symbol of remarkable biodiversity and ecological importance [1]. However, the convergence of zoonotic diseases and environmental degradation poses significant challenges to both human health and sustainable development in this area [2]. Specifically, the Hainan tropical rainforest is confronted with the prevalence and transmission of diseases such as Dengue Fever, which is propagated by the rapid proliferation of Aedes aegypti mosquitoes, and Malaria, facilitated by favorable breeding conditions for Anopheles mosquitoes in the humid rainforest environment [3,4,5]. There are also concerns regarding the transmission of the COVID-19 virus, as interactions between humans and wildlife, along with unhygienic market conditions, can facilitate zoonotic spillover events [6, 33,34,35].

Fig. 2
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Main plant and animal species in Hainan tropical rainforests. The picture of Hainan peacock pheasant was provided by **wen Chen, taken in Jianfengling area of National Pack of Hainan Tropical Rainforest

Plant communities in the Hainan tropical rainforest

The Hainan tropical rainforest harbors a wide range of plant species, including several endemic ones that are exclusive to this region. Cycas hainanensis and Hainan hopea (Hopea hainanensis) are notable examples of such endemics [36, 37]. The rainforest’s dense canopy, formed by towering trees that can exceed 30 m in height, creates a complex vertical structure, providing diverse microhabitats for a variety of organisms. Numerous plant species contribute to the rich biodiversity of the rainforest.

One prominent tree species in the Hainan tropical rainforest is the Hainan hopea. Known for its hard and durable wood, it serves as a keystone species, providing habitat and contributing to the forest’s structural integrity [38]. The Hainan hopea plays a vital ecological role by supporting various wildlife species through habitat provision and resource availability [39]. Due to its slow growth and limited distribution, it is considered a protected species in China. Conservation efforts are in place to ensure the sustainable management of this iconic plant species in Hainan.

Another representative plant species found in the Hainan tropical rainforest and other parts of China is Alsophila spinulosa, commonly known as the Chinese tassel fern [40]. Belonging to the family Cyatheaceae, this large, perennial fern can reach heights of up to 10 m. The delicate and feathery appearance of its fronds, along with their vibrant green color, distinguishes it. Alsophila spinulosa thrives in moist and shady environments, often growing in the understory of tropical rainforests [41]. In the forest ecosystem, it plays a crucial ecological role by providing habitat for various organisms. Additionally, its fronds contribute to leaf litter, enriching the soil and supporting the growth of other plants. Conservation efforts are in place to protect Alsophila spinulosa due to habitat loss and collection for horticultural purposes [42]. The sustainable management of this beautiful fern species and the preservation of its natural habitat are vital for its long-term survival.

Cycas hainanensis, also known as the Hainan cycad or Hainan sago palm, is a species of cycad plant native to the tropical rainforests of China. Belonging to the Cycadaceae family, it exhibits a slow growth rate and retains its evergreen foliage. The plant features a robust trunk and large, pinnate leaves resembling palm fronds. Cycas hainanensis thrives in the tropical climate of Hainan Island, particularly in areas with partial shade and well-drained soil. It is commonly found in lowland forests and rocky hillsides. This cycad species holds the status of a living fossil, having existed for millions of years, thus rendering it a significant subject for scientific research and conservation efforts [43]. However, due to habitat loss and illegal collection for ornamental purposes, Cycas hainanensis is now classified as a protected species in China. To ensure its survival, conservation initiatives such as habitat preservation, captive breeding, and public awareness campaigns are being implemented.

Dacrydium pierrei, a coniferous tree belonging to the Podocarpaceae family, is characterized by its vibrant green leaves, reminiscent of the plumage of a bird known as the “Lujun bird.” This resemblance has led to its common name. Native to the mountainous regions of central and southern Hainan Island in China [44]. Pierre’s podocarp possesses a unique attribute: when wounded, it exudes red resin, earning it nicknames like “Tears-of-balsam” or “Red pine”. This resinous secretion holds both cultural and commercial significance. To address conservation concerns, protected areas have been established in the primary habitats of Dacrydium pierrei, such as Jianfengling and Bawangling [45]. These protected areas employ various measures, including artificial regeneration and facilitation of natural regeneration, to restore and conserve this species.

Animal biodiversity of the Hainan tropical rainforest

The Hainan tropical rainforest harbors a diverse array of remarkable and endangered animal species, including the critically endangered Hainan gibbon (Nomascus hainanus). With an estimated population of fewer than 40 individuals, the Hainan gibbon’s presence is crucial for maintaining the ecological equilibrium of the rainforest [46, 47]. Another endemic subspecies found in this region is the Hainan black crested gibbon (Nomascus sp. cf. nasutus hainanus), known for its distinctive vocalizations and significant role in seed dispersal, which influences forest regeneration [48, 49].

The Hainan tropical rainforest is also home to other notable animal species such as the Hainan Eld’s deer (Rucervus eldii hainanus), a critically endangered subspecies characterized by its light brown or reddish-brown coat with white spots and a distinctive throat mane in males. Habitat loss and poaching have led to its critical endangerment, as recognized by the International Union for Conservation of Nature (IUCN) [50]. Additionally, the Hainan black pig, adapted to the forest environment and displaying a smaller body size, contributes to the rainforest’s unique biodiversity [51].

Among the avian species, the Hainan Partridge (Arborophila ardens) stands out as a unique bird endemic to the high-altitude mountainous regions of the Hainan tropical rainforest [52]. Its dense brown feathers with speckled patterns aid in camouflage within the forest environment. While both males and females share a similar appearance, males possess a patch of red bare skin on their heads, adding vibrancy to their overall appearance [53]. Typically observed in pairs or small groups, the Hainan Partridge faces endangerment due to habitat destruction and human disturbance. Consequently, it is assessed as an endangered species by the International Union for Conservation of Nature [1].

The Hainan Peacock Pheasant (Polyplectron katsumatae) is another endemic bird species found exclusively in the Hainan tropical rainforest [54]. This pheasant species, belonging to the Phasianidae family, is admired for its striking plumage and elaborate courtship displays [55]. However, like many other pheasant species, the Hainan Peacock Pheasant is vulnerable to habitat loss and hunting pressures. Therefore, it is considered a protected species in China, necessitating conservation efforts through protected areas and raising awareness about the importance of preserving this unique bird [34].

The Hainan tropical rainforest encompasses a wealth of significant plant and animal species, many of which are endemic and play vital roles in maintaining the ecological balance of the region. Protecting and conserving these unique species and their habitats is essential for the sustainable development of the Hainan rainforest ecosystem in the long term. Collaborative efforts involving scientific research, community engagement, and policy support are key to preserving and managing this valuable natural resource.

Microbial communities and their ecological roles in tropical rainforests

Microorganisms play a crucial role in tropical rainforest ecosystems, contributing significantly to vital processes such as the decomposition of organic matter, nutrient cycling, and the stability of the ecosystem. Additionally, microbial communities enhance biodiversity and promote species adaptability, highlighting their essential regulatory role within these ecosystems [56].

Recent studies have shed light on the complex interactions between microbial communities and tropical rainforest ecosystems. For instance, Soong et al. demonstrated that microbial communities are key drivers of carbon cycling in tropical rainforests. Specific microbial taxa play significant roles in regulating carbon storage and release [57]. Furthermore, Deng et al. found a positive correlation between microbial biodiversity in the rhizosphere of tropical plants and plant health and productivity. This highlights the importance of plant-microbe interactions in sha** rainforest ecosystems [146].

In conclusion, the One Health approach has proven effective in addressing public health challenges in the Hainan tropical rainforest region. Its interdisciplinary nature and collaborative efforts are essential for understanding and mitigating the complex interactions between human, animal, and environmental health. By expanding the application of the One Health approach to other biodiverse ecosystems, we can enhance global infectious disease surveillance, conservation efforts, and sustainable development practices that prioritize the well-being of both humans and the environment.

In addition to the integrated disciplinary approach for conserving the tropical rainforest biosphere, another study aims to develop a tool based on the One Health concept for government utilization in public health security testing [147]. This tool assesses the potential risks of severe zoonotic diseases associated with wildlife trade, providing valuable information for the formulation of stringent regulation and control policies. Furthermore, several urgent plans are underway to address the changes occurring in the tropical rainforest, including the United Nations Decade on Ecosystem Restoration and the accelerated progress towards the Bonn Challenge [148, 149]. These plans aim to restore 350 million hectares of degraded and deforested land by 2030, thereby mitigating the destructive impact of deforestation-induced climate change on the tropical rainforest. Additionally, community participation, outreach, and capacity-building are vital cross-cutting components of effective One Health programs [150]. These initiatives equip local populations with the necessary knowledge and resources to promote health at both the individual and ecosystem levels. While specific ecological, cultural, and socioeconomic contexts may vary, the fundamental principles of One Health, including interdisciplinary cooperation, scientific research, and proactive risk mitigation, are broadly applicable across diverse settings worldwide. Integrating One Health principles into national and global policy agendas is crucial for addressing existing and emerging public health challenges at the interface of humans, animals, and the environment on a global scale.

The urgency and importance of addressing public health issues in the Hainan tropical rainforest region cannot be overstated. It is crucial to emphasize the need for increased efforts from the government, academia, and society at large to promote and support initiatives aimed at sustainable development and health improvement in this region [151]. Multiple studies and literature reports have highlighted the public health concerns in the Hainan tropical rainforest region. For example, researchers investigated the prevalence of zoonotic diseases in the wildlife of this region, highlighting the potential risks for human health [152, 153]. Additionally, scholars conducted research on the impact of deforestation on vector-borne diseases, demonstrating the close relationship between environmental changes and human health outcomes [154, 155]. In recent years, tropical rainforests have witnessed rapid environmental changes, including deforestation, habitat destruction, and climate change, among others [156]. These changes have had multifaceted impacts on human health [157]. As early as 2000, researchers investigated the correlation between environmental changes in the Amazon rainforest and human health [158]. They found that extensive development and deforestation in the Amazon River basin have led to the emergence of new diseases and the increased difficulty of controlling existing diseases. The excessive exploitation of tropical rainforests can also heighten human contact with wildlife, thereby increasing the risk of zoonotic diseases crossing species barriers and transmitting to humans [159, 160]. Recent outbreaks of new infectious diseases such as Ebola and Zika virus have been closely associated with activities in tropical forest regions [161, 162]. Furthermore, excessive deforestation of rainforests can disrupt the activity of vector organisms like mosquitoes, leading to more frequent occurrences of diseases such as malaria and dengue fever [64]. Additionally, climate change is expanding the geographical distribution range of these diseases. These findings underscore the necessity of adopting a comprehensive One Health approach to address the public health challenges in the Hainan tropical rainforest region. However, it is important to acknowledge that there is still progress to be made in implementing One Health practices in the Hainan tropical rainforest. For example, Wang and Zeng, using the Policy Modeling Consistency (PMC) index model, have pointed out that the policies of the Hainan Tropical Rainforest National Park are not sufficiently effective in terms of social and economic outcomes [126]. In comparison to Hong Kong and Singapore, the policies related to the Hainan Tropical Rainforest National Park lack adequate incentives and strategic guidance, primarily due to the absence of descriptive and predictive macro-strategic design [126]. This observation provides us with valuable recommendations and food for thought. By combining efforts from multiple disciplines, we can develop strategies that promote sustainable development, protect biodiversity, and improve the overall health and well-being of the local population in Hainan.

Conclusion

The tropical rainforests in Hainan are confronted with several critical public health issues that demand immediate attention. These issues include emerging infectious diseases, vector-borne diseases, and the health consequences of environmental degradation. This review discusses the risks posed to human populations in the region by zoonotic diseases such as hantavirus and potential novel coronaviruses originating from wildlife. Furthermore, the favorable climate in Hainan promotes the proliferation of disease-transmitting mosquitoes, which facilitate the transmission of diseases like dengue fever and malaria between humans and wildlife. Deforestation and habitat destruction have also contributed to the increase in disease vectors.

The implementation of the One Health approach offers an effective framework to address these interconnected challenges. As exemplified by the experiences in Hainan, key components such as enhanced disease surveillance, interdepartmental coordination, ecological conservation, and public engagement play vital roles. By adopting a collaborative and multidisciplinary strategy, early identification of public health threats and their mitigation through rapid response can be achieved. However, sustained efforts are necessary to involve local communities more extensively in environmental and public health initiatives.

The public health issues examined in the Hainan tropical rainforest underscore the relevance of One Health approaches in various ecosystems worldwide. Similar human-animal-environment interfaces, as observed in regions like the Amazon rainforests, can facilitate the emergence and transmission of zoonotic diseases. By implementing integrated surveillance, conservation measures, and community engagement within a One Health framework, effective preparedness and response can be ensured, spanning from remote forests to urban areas. While specific ecological and socioeconomic contexts may differ, the core principles of interdisciplinary collaboration, research, education, and communication inherent in One Health are broadly applicable across different settings. At local, national, and global levels, policy initiatives embracing the One Health approach have immense potential to cultivate resilient communities and environments worldwide. Addressing complex health challenges at the intersection of humans, animals, and nature necessitates a sustained commitment to cross-sectoral partnerships and evidence-based interventions.

Overall, this review emphasizes the urgency of prioritizing ecosystem and public health in Hainan’s tropical rainforests. While progress has been made in applying One Health principles, there are opportunities to strengthen long-term policies and frameworks to promote sustainability. Future priorities involve conducting further research on disease ecology, bolstering conservation measures, and improving health infrastructure and education. The One Health approach will continue to serve as a comprehensive model for balancing human welfare, animal health, and ecological well-being in this unique region.