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The nexus between forests and human health

Forests cover nearly one third of the land on Earth. They provide, directly or indirectly, important health benefits for all people. The World Health Organization (WHO) defines health as ¡°a state of complete physical, mental and social well-being and not merely the absence of disease or infirmity¡±. Thus, the concept of health includes not only the treatment of illness, but also disease prevention and well-being.

The type and intensity of the health benefits of forests vary depending on rural and urban distinction and the proximity of human settlements to forests. Broadly, such benefits include nutrition, and the prevention and treatment of illness. Firstly, forests are direct sources of nutritious foods and medicinal plants, and of fuel for sterilizing water. With malnutrition being the primary cause of immunodeficiency worldwide, healthy diets are critical for human health. Secondly, forests provide essential ecosystem functions that sustain food production: their contribution to freshwater availability, soil fertility and biodiversity are essential to sustaining global food supplies. Finally, forest-centred activities support mental health by reducing stress and anxiety, and they can mitigate the effects of depression and other mental health issues.

For people living in or near forests, further health benefits include the availability of a wide variety of nutrient-rich forest foods, including fruits, leaves, nuts and seeds, mushrooms, honey, wild meat and insects. While forest foods may play a small role in providing calories, they form a critical part of diets commonly consumed by rural populations, who are often poor and food insecure. Forests are also a source of medicinal plants. WHO estimates that at least 80 per cent of the world¡¯s population depends on traditional medicine to meet primary health-care needs. Local knowledge of medicinal plants constitutes a major part of traditional health-care systems. Over 1 billion people worldwide use herbal and home remedies to treat children¡¯s diarrhoea. Furthermore, forests provide woodfuel for cooking¡ªa benefit that comes with risks. Globally, over 75 per cent of rural households as well as 20 per cent of urban households depend primarily on woodfuel for cooking, and 10 per cent of the global population uses woodfuel to boil water to make it drinkable. Smoke from such solid fuels, however, can lead to increased risk of various illnesses, such as strokes and pulmonary diseases, including lung cancer. Finally, forests often have cultural significance that is key to the health of individuals and communities living in and near forests. Indigenous people often associate the well-being of the forest with enhanced collective and community well-being in a larger sense, perceiving a link between healthy land and healthy people. In such cultures, forest degradation and deforestation have been observed to cause negative mental health issues.

Forests cover nearly one third of the land on Earth. They provide, directly or indirectly, important health benefits for all people.

For people living in urban areas and in industrialized societies, the health benefits are somewhat different. Similar to rural populations, direct consumption of forest foods is also an important health contribution for urban dwellers. Urbanization is generally associated with a nutritional transition resulting in higher consumption of sugars and processed foods, which, combined with limited physical exercise, contributes to the global increase in overweight, obesity and associated non-communicable diseases. Forest foods can help counter this trend by providing diverse nutritious alternatives. Furthermore, forests play a major role in the development of plant-based pharmaceutical products, although the benefits of these go disproportionately to countries that host pharmaceutical companies rather than to the countries of origin. Developing countries provide two thirds of the plants used in modern systems of medicine. Increasing evidence shows a positive relationship between exposure to forests and mental, physical, social and spiritual well-being¡ªall interlinked cornerstones of good health. Studies from China, Japan and the Republic of Korea have shown that a visit to a forest environment lowers blood pressure and pulse rate; reduces cortisol levels; suppresses activity of the sympathetic nervous system, which controls the ¡°fight, flight or freeze¡± response when people are faced with potential danger; and enhances the activity of the parasympathetic nervous system, which inhibits the body from overworking and restores it to a calm and composed state. Finally, forests in and around urban areas provide preventive health benefits through recreational activities, and mitigate the negative impacts of pollution and heatwaves.

Current challenges

There are a number of trends that are eroding the health benefits of forests. The combination of deforestation, climate change, urbanization and economic growth in many developing regions is causing a shift in the diets of rural communities who live in or near forests. The reduced availability of land and access to forest foods, and increased income and availability of processed foods, are resulting in an increase in consumption of calorie-rich foods and a movement away from traditional diets. These factors are contributing to rising rates of overweight and obesity as well as associated non-communicable diseases. This is particularly damaging when rates of infectious diseases remain high due to limited hygiene and health services. Furthermore, the same trends of deforestation, climate change and urbanization are causing imbalances in forest-centred ecosystems, such as changes in the abundance or spread of certain species, which result in an increased likelihood of the emergence of pathogens that could further harm the ecosystem or humans through new zoonotic diseases. For example, alterations to the landscape, such as the building of roads and agricultural conversion, have led to outbreaks of malaria, while diseases such as HIV and Ebola originated from close contact with wild animals. In fact, around .

Actions we can take as a global community

Ensuring the continuation and enhancement of forest benefits for human health requires a combination of preserving ecosystems, sustainably managing resources and safeguarding continued equitable access to forest benefits, especially in the face of climate change. The global community, and national policymakers in particular, need to adopt a multifaceted ¡°One Health¡± approach that views human, plant and animal health as intertwined and codependent. Forest resources need to be managed sustainably, and where forests are converted to other land uses (e.g. for agriculture or urban needs), the changes must be made in ways that minimize disruption to wildlife and the ecosystem to avoid the emergence of diseases. Investments in better data and measurement of the health benefits of forests are needed, and indicators on human, forest and animal health need to be analysed jointly as part of cross-sectoral policy processes. It is the responsibility of the United Nations and its specialized agencies to support countries in advancing this agenda for the sake of our health and that of future generations.