Biodiversity Impacts Human Health: Mechanism,Hypothesis,and Key Issues

ZHONG Le,ZUO Zitong,ZHAO Zhicong,CHEN Siqi

Biodiversity is closely related to human health.Both biodiversity conservation and Healthy China are national strategies and major projects for China.Therefore,the paper attempts to answer the following questions: 1) What is the understanding of the relationship between biodiversity and human health in modern medicine and nature conservation research? 2) What are the mechanisms and hypotheses of existing research on how biodiversity affects human health? 3) What key questions still need to be studied under the direction of research on biodiversity impacting human health? 4) How to transform the research results and build a green space that relies on biodiversity to improve the health level of the population through landscape architecture planning and design?

1 Cognitive Process

1.1 Medical field

The modern medical knowledge of biodiversity for human health has undergone a long development,and three mainstream ideas of holistic health have emerged: ＂One Health＂,＂EcoHealth＂and ＂Planetary Health＂.

The commonality lies in the fact that all emphasize the synergy of human health with nonhuman life forms and the natural environment.The differences are: the ＂One Health＂ research mostly uses zoonotic diseases,pathogens,animals,etc.as keywords,with few ecological keywords,and the discipline categories are mainly medical and veterinary;the ＂EcoHealth＂ research includes multiple groups of keywords from ecological perspectives,such as zoonotic diseases,ecosystem health,biodiversity,and disease ecology,with environmental science as the main focus;the＂Planetary Health＂ research focuses the study of human beings,with fewer animal and disease keywords,but emphasizes environmental factors,and is dominated by medical and social sciences.

1.2 Field of nature protection

Experts in the field of nature conservation have also undergone a process of increasing awareness of biodiversity for human health.Human healthrelated requirements have continued to appear in COP decision documents beginning with the sixth Conference of the Parties to theConvention on Biological Diversity(CBD COP6) in 2002.

In the field of nature conservation,biodiversity contributes to human health at individual,community and planetary scales.Specifically,its contribution is manifested in 1) water and air,2) food and nutrition,3) disease regulation,4) medicine and medical,and 5) health promotion in physical,psychological,and cultural dimensions.

CBD and WHO have worked closely together since 2005,establishing partnerships with the International Union for Conservation of Nature(IUCN),the Food and Agriculture Organization of the United Nations (FAO),the ASEAN Center for Biodiversity,and the Consortium of Universities for Global Health,publishing a series of guidelines and reports on the impact of biodiversity on human health,and jointly establishing the Interagency Liaison Group (ILG) on Biodiversity and Health in 2017.

2 Medical and Psychological Hypotheses and Theories on Biodiversity for Human Health

2.1 Positive impact

1) Effect on physiological health.

The Hygiene Hypothesis states that people who experience more microbial exposure during early childhood may be less likely to develop immune hypersensitivity reactions later in life.

The Old Friend Hypothesis centers on the idea that some microorganisms are recognized by the innate immune system as harmless ＂old friends＂ that drive the maturation of regulatory T cells (Treg) in the innate immune system,thereby avoiding a range of immune regulatory disorders and autoimmune diseases.

The Biodiversity Hypothesis suggests that biodiversity loss and inflammatory diseases are linked to global megatrends and that biodiversity loss leads to a reduction in the human microbiota,resulting in ＂microbial deprivation＂,which in turn leads to immune dysfunction and disease.

The mechanism of the Dilution Effect lies in the ability of high biodiversity levels to reduce the density of ideal hosts and vectors and their probability of contact with pathogens,to change the living conditions of ideal hosts or vectors,and to regulate the populations of ideal hosts or vectors through predation,predation,competition,and other interspecific relationships.

2) Effect on mental health.

The Biophilia Hypothesis,and the Stress Recovery Theory have focused on the effects of biodiversity on human mental health.The Attention Recovery Theory only discusses the influence of the natural environment on mental health and does not directly elucidate the role of biodiversity.

2.2 Negative impact

The negative impact of biodiversity on human health has received less attention,and there are fewer theoretical mechanisms by which biodiversity damages human health.Among a limited number of theories,the Amplification Effect,which is the opposite of the dilution effect and is based on the＂diversity begets diversity＂ model,acts on physical health.

The Stress Recovery Theory acts on mental health.The latter suggests that large predators,snakes,spiders,etc.are perceived as threats by humans,causing negative emotional and behavioral responses such as disgust and fear,which lead to stress.

3 Key Issues

3.1 Interpreting the phenomenon

1) Direct correlation between biodiversity and human health.It includes quantitative verification of the direct correlation between specific species,population structure,diversity indicators,and other specific biodiversity characteristics and various dimensions of human health,such as the interpretation of correlations,strength of correlations,and expression patterns.

2) The true effect of biodiversity characteristics on human health.The effects of confounding variables need to be removed and the direct effects of biodiversity need to be measured.

3) Disservices of biodiversity on human health.There is a need to study the type,intensity,and consequences of these negative impacts,as well as the environmental conditions and patterns of action that lead to their occurrence.

4) Impacts of biodiversity on long-term health.It is necessary to test whether there is a long-term sustained effect of the impact of biodiversity on human health,measure the duration of the longterm effect,and explore the law of the evolution of the impact effect over time.

5) The complex effects and effects of biodiversity change on human health.It is necessary to verify the effects of biodiversity changes on human health at different levels,such as species change,population structure change,and interspecific relationship change.

3.2 Theoretical mechanism

1) Testing and perfecting the existing theoretical hypothesis.It includes the time scale,space scale,biological community condition and specific law of dilution effect and amplification effect,and the critical condition of dilution effect and amplification effect transformation.The Hygiene Hypothesis,the Old Friend Hypothesis,and the Biodiversity Hypothesis were tested and refined.The Biophilia Hypothesis,Stress Recovery Theory and Attention Recovery Theory were tested at the biodiversity level rather than at the green space level.

2) The transmission of biodiversity at multiple scales and the mechanism of its impact on human health.The main focus is on the ＂macro biodiversity -microbial diversity -human microbial environment -human health＂ connection and mediating mechanisms.

3) Causal pathways through which biodiversity affects human mental health and social health.The paper explains how biodiversity affects molecules,cells,brain tissue areas,and the whole brain from the perspective of the intersection of Medicine,Psychology,Cognitive Science,and Neuroscience,and the Brain Mechanisms that affect mental health and social health.

4) The ＂dose-response＂ relationship of biodiversity exposure on human health.It is necessary to study the health effects of different combinations of biodiversity exposure characteristics on different populations,including the effect sizes,mediating pathways,and mechanisms of effects.

5) The mediating mechanisms of perceived biodiversity on human health.It is necessary to examine what types and intensities of differences exist between perceived biodiversity and real biodiversity indicators,propose the mediating mechanisms of perceived biodiversity effects on human health,and measure the effect sizes of the effects.

3.3 Adjustment optimization

1) Cost and benefit analysis of biodiversity conservation about human health.This study explores whether the inclusion of human health dimensions alters the costs and benefits of biodiversity conservation.It focuses on accurately identifying and calculating these changes.

2) Trade-offs between the costs and benefits of biodiversity conservation from a human health perspective.It mainly includes the methods and technical routes to weigh the cost and benefit of protection.The range of time and space that is taken into account when making trade-offs.

3) Human adaptation to,regulation of,and consequent health effects of changes in biodiversity.When biodiversity changes,whether the measures taken by humans to adapt and regulate the changes have an impact on health levels.

4) Holistic health thinking in synergy between biodiversity and human health.Specifically,it includes how to implement the whole health idea of the One Health,EcoHealth,Planetary Health,etc.In the context of the new era of ecological civilization,how to integrate multi-disciplines and develop new holistic health ideas.

5) Pathways for the transformation of specific biodiversity indicators for human health into green spatial environmental features.This includes how to image the threshold value of specific biodiversity indicators that are beneficial to human health into the natural environmental characteristics of green spaces,how to build green spaces with these characteristics through planning and design,and so on.

4 Implementation Path

4.1 Form a planning and design mechanism for multi-disciplinary integration and multi-industry cooperation

One is the integration of multiple disciplines.The synergy between biodiversity and human health involves many disciplines,which can be divided into front end,middle end and back end according to the stage in which biodiversity plays its main role.The front end interprets phenomena and finds problems,and evaluates health risks and explores health hidden dangers by relying on the power of Epidemiology,Public Health and other disciplines.The middle end is to reveal the mechanism and analyze the problem,mainly relying on the strength of Medicine and Veterinary Medicine,deeply explore the causes of health risks and health hazards,etc.,and propose possible directions to eliminate risks.The backend is practice transformation and problem solving,which mainly relies on the strength of disciplines such as Landscape Architecture and Urban and Rural Planning to convert theoretical hypotheses on eliminating health risks and hidden dangers into practical operational strategies.

Second,to form cross-industry cooperation.In particular,it is necessary for practitioners to scientifically understand the role of biodiversity exposure in promoting human health,and to provide professional advice to patients or people in need to rely on biodiversity exposure in the treatment process to enhance healing and promote health.

4.2 Take population health as a key component of planning and design goals and include it in the whole planning and design process

Population health needs to be one of the core objectives of the planning and design system,and it needs to be implemented in the whole process of planning and design through evidence-based planning and design tools.In the status quo analysis phase,the potential health impacts,and actual or potential health promotion effects of the site base need to be investigated and assessed,and the health status and future needs of existing and potential client groups need to be investigated and analyzed.In the planning and design phase,potential conflicts between different objectives such as biodiversity,health,aesthetics,and culture need to be identified and weighed,emphasizing the synergy between biodiversity and population health,and maximizing the health benefits for the population while protecting and enhancing the level of biodiversity in green spaces.

5 Conclusion

Under the background that ＂harmony between humans and nature＂ has become one of the five characteristics of Chinese modernization,it is important to explore the relationship between humans and nature in the context of health.To take advantage of the latter,this paper systematically compares the development of international knowledge on the relationship between biodiversity and human health,summarizes the relevant medical and psychological hypotheses and theoretical models,and proposes the key scientific issues that need to be solved and the main realization paths for the discipline of landscape architecture.Since the goal of this paper is to introduce the topic of＂biodiversity and human health＂ comprehensively and systematically,a certain degree of research precision is inevitably lost while providing a panoramic view of the topic,and further research is needed.