I love this video that parodies drug ads using nature. It’s kind of silly, but a lot of what is said in the video is actually backed up by research that shows nature is good for your mental health (research showing nature’s effect in quelling murderous rage is harder to find.)
Studies have shown that even getting outside for a little bit during the workday can help you clear your mind and de-stress. In some places, doctors have actually begun prescribing nature to patients rather than drugs. In that sense, our investment in parks and trees should be seen from a public health perspective as well as from a recreation, social, and ecological perspective. In fact, in the US money for park improvements does sometimes come from the health sector, like this potential greenway in Minneapolis.
Charles Montgomery writes a lot about the happiness-inducing effects of nature in the city in his book Happy City, which is well worth a read. And you should read it while sitting outside in a park.