Scientists assess the benefits offered by forests, trees and green spaces for human health

The global scientific evidence of the multiple types of benefits that forests, trees and green spaces have on human health has now been assessed by an international and interdisciplinary team of scientists. The outcome is presented in a major report titled "Forests and Trees for Human Health: Pathways, Impacts, Challenges and Response Options" by the Global Forest Expert Panels (GFEP) Programme of the International Union of Forest Research Organizations (IUFRO). IUFRO unites more than 15,000 scientists in more than 630 member organizations – mainly public research centers and universities – in 115 countries and is a member of the International Science Council.

Existing evidence strongly supports a wide range of physical, mental, social and spiritual health benefits associated with forests and green spaces. They have positive effects, e.g., on the neurodevelopment in children, on diabetes, cancer, depression, stress-related disorders, cognitive aging and longevity, and are critical for enhancing social interactions, recreation and relaxation. Although all life stages are impacted, starting from the prenatal stage, the significant effects on children are particularly important, not least because of repercussions in later life.

Evidence highlighted in the report includes that no less than 24% of global deaths (and 28% of deaths among children under five) are due to negative environmental factors such as air pollution and extreme weather events. Premature death and disease can be prevented through healthier environments worldwide.

Forests, trees and green spaces not only provide healthier environments but also numerous goods and services, including medicines, nutritious foods, and other non-wood forest products that contribute to human health. Medicinal plants, which are particularly important to Indigenous Peoples and Local Communities (IPLCs), provide basic health care for 70% of the world's population.

Forests, trees and green spaces also help reduce the negative health impacts of climate change. In cities, for example, green spaces and trees have a significant cooling effect, which is particularly important as more frequent heat waves are expected, greatly increasing the risk of heat stress and heat stroke.

This peer-reviewed assessment is the most comprehensive on this topic to date and has been carried out by the Global Forest Expert Panel (GFEP) on Forests and Human Health in the frame of the IUFRO-led Joint Initiative of the Collaborative Partnership on Forests (CPF). A total of 44 scientists and experts have contributed to this assessment, with a core Expert Panel of 16 scientists with diverse expertise, including forestry, ecology, landscape design, psychology, medicine, epidemiology and public health. Authors and reviewers are from across the globe and represent different genders.

The scientists took a broad view of forests, trees outside forests and green spaces, and looked at them in diverse contexts, with a focus on urban, rural, and forest-dependent communities. Equally, they took a broad perspective of human health, including all aspects of people's physical, mental, spiritual and social health and well-being, while also considering links to the health of other beings and ecosystems.

The report underpins a One Health perspective, which recognizes that the health of humans, animals, plants, and the wider environment are closely linked and interdependent. It suggests that decision-makers in forest, health and related domains should also adopt more integrative perspectives for addressing forest-human health relations. By linking forest and human health policies and strategies, new and innovative solutions for health and forest challenges can be identified."

Panel Chair Cecil Konijnendijk, University of British Columbia, Canada

The report highlights the important contribution of forests and trees to the United Nations' 2030 Agenda for Sustainable Development and its goals, particularly Goal 3 (SDG 3), which aims to "ensure healthy lives and promote well-being for all at all ages."

While most of the health outcomes of forests, trees and green spaces are positive, there are also some negative impacts that need to be considered and mitigated. Human health can be impacted adversely through allergies, diseases transmitted by animals or reduced air quality because of forest fires, for example. Global crises such as climate change, land-use change, urbanization and biodiversity loss endanger the important role that forests and trees provide as 'safety nets' for the food security and livelihoods of vulnerable populations.

These negative impacts are mostly due to factors such as disturbed relationships between forests and people, poor forest conservation and management, or inappropriate choice of tree species in areas where people live. Decision-makers should promote and enhance positive forest and tree health outcomes while minimizing and managing potential negative impacts, especially on vulnerable populations.

A solution to the malaria epidemic, for example, is not to eliminate the forest and wetland habitats of the mosquitos transmitting the disease - deforestation can actually increase the malaria risk - but to invest in sustainable forest management and urbanization processes that avoid loss of natural habitats.

Another example of a misconception related to harmful consequences of nature is the attribution of the increase in pollen allergies to urban forests and green spaces. In fact, allergic diseases are more prevalent in high-income countries, often caused by unhealthy lifestyles disconnected from nature, and exacerbated by climate change as warmer temperatures prolong the pollen season.

As the acceleration of negative global trends and challenges including climate change and pandemics alters and intensifies the importance of forest-human health relations, urgent action is required. Climate change, urbanization and lifestyles that are disconnected from nature are among the main reasons behind many of the health challenges that societies around the world are facing today, including malnutrition, cardiovascular diseases and mental health problems. Environmental and climate disruptions have also led to a surge in life-threatening diseases such as Ebola or avian flu. Land-use change is estimated to have caused the emergence of more than 30% of new diseases since 1960.

These trends are not only putting human health at risk but also that of forests and trees as they are among the drivers behind wildland fires, heavy storms and forest pests, for example. It is therefore crucial to improve the understanding of the role of nature in providing benefits to humans, and consequently, the role that ongoing nature destruction is playing in increasing health hazards.