"Many people," says Dr. Eeva Karjalainen, of the Finnish Forest Research Institute, Metla, "feel relaxed and good when they are out in nature. But not many of us know that there is also scientific evidence about the healing effects of nature."

Forests -- and other natural, green settings -- can reduce stress, improve moods, reduce anger and aggressiveness and increase overall happiness. Forest visits may also strengthen our immune system by increasing the activity and number of natural killer cells that destroy cancer cells.

Many studies show that after stressful or concentration-demanding situations, people recover faster and better in natural environments than in urban settings. Blood pressure, heart rate, muscle tension and the level of "stress hormones" all decrease faster in natural settings. Depression, anger and aggressiveness are reduced in green environments and ADHD symptoms in children reduce when they play in green settings.

In addition to mental and emotional well-being, more than half of the most commonly prescribed drugs include compounds derived from nature -- for example Taxol, used against ovarian and breast cancer, is derived from yew trees, while Xylitol, which can inhibit caries, is produced from hardwood bark.

Dr. Karjalainen will coordinate a session on the health benefits of forests at the 2010 IUFRO World Forestry Congress in Seoul. "Preserving green areas and trees in cities is very important to help people recover from stress, maintain health and cure diseases. There is also monetary value in improving people's working ability and reducing health care costs." she says.