Forests are indispensable to human health: Their protection, management, and restoration support disease regulation, nutrition, and more. But what exactly is the science behind forests and human health? And why is the connection so essential?
hrough extensive investigation, WWF uncovered ample evidence that forests provide, prevent, and heal. Public health and forests are entwined—at the local, regional, and global scale.
In the new report The Vitality of Forests, WWF examined five categories of interactions between forests and human health: noncommunicable diseases, environmental exposure (pollution), food and nutrition, physical hazards, and infectious diseases. With climate change exacerbating many of these categories, the report also highlights the important role forests play in the resilience of human health to climate change.
1. Forests reduce risks associated with some major noncommunicable diseases.
Each year, 41 million people die from noncommunicable diseases. These are noninfectious diseases that cannot be transmitted between people and include cardiovascular diseases, cancers, chronic respiratory diseases, diabetes, and mental health issues. Noncommunicable diseases are the fastest-growing and largest health burden globally, and 77% of deaths from noncommunicable diseases are in low- and middle-income countries. Exposure to forests may reduce some of the factors that elevate the risks of noncommunicable diseases, and human stress hormones—such as cortisol, progesterone, and adrenaline—respond significantly when a person spends time in a forest.
2. Forests clean air and water and reduce the risks of infectious and noncommunicable diseases.
In 2015, air pollution (ambient and household) accounted for 6.5 million deaths, with noncommunicable diseases accounting for most of the disease burden. By filtering pollutants from air and water, forests help reduce the threats of pollution-related infectious diseases and noncommunicable diseases, including diarrheal disease, cancers, and respiratory diseases.
Conserving or restoring upstream tree cover is critical for the health and well-being of children around the globe. Diarrheal disease is the second-leading cause of death and the leading cause of malnutrition in children aged under five years worldwide. Research demonstrates that upstream tree cover is associated with a lower prevalence of diarrheal disease (linked to water pollution) in children downstream. A 30% increase in upstream tree cover is linked to a 4% reduction in the probability of diarrheal disease—similar to the effects of an improved sanitation facility.
3. Forests positively impact nutrition and food security.
Forests can offer a nutritional safety net. Each year, 3.1 million children worldwide die from undernutrition while those that survive with poor nutrition during the first 1,000 days of life often suffer lifelong health, social, and financial challenges. Children with adequate nutrition will have improved cognitive and physical development as well as lower risk of morbidity and mortality.
4. Forests can protect people from the impacts of disasters.
Between 1996 and 2015, 1.3 million deaths were directly attributed to disasters or hazards such as wildfires, flooding, and extreme heat. As the planet faces a rise in extreme heat—affecting 1.7 billion people between 1983 and 2016—the cooling potential of forests is essential in battling the direct risk of heat-related illnesses such as heatstroke but also the impact that excessive heat has on exacerbating respiratory and chronic cardiovascular conditions.
5. Forests mediate the emergence and spread of zoonotic infectious diseases and are our first line of defense against new infectious diseases.
Nearly one in three outbreaks of new and emerging diseases are linked to land-use change, including deforestation. Infectious diseases are the leading cause of death in low-income countries and the leading cause of death of children aged under five years globally. For Ebola, the relative importance of forest loss was found to be greater than 60% independent of other factors.
Intact forest landscapes allow animals the habitat they require to maintain distinct populations and limit the ability of infectious diseases to spread among and between species. Forest loss and degradation concentrates animal populations, which has led to the emergence of novel infectious diseases that can have dramatic impacts on people and society.
6. Forests help mitigate climate change and its adverse health effects.
Importantly, the role climate change plays in human health is woven throughout this report. We know that our exposure to physical hazards like heat and more severe storms and floods will increase and the habitat of common vectors of infectious diseases like mosquitoes and ticks will expand. We also know the nutritional content of staple foods will decrease as CO2 in our atmosphere increases. And we know that people are more vulnerable to climate change if their health is already compromised. For each of these impacts, forests represent an indispensable solution to mitigating and adapting to climate change while also supporting the health and well-being of people.