As it turns out, humans may actually require green spaces for optimal health and longevity. K. Springer photo

Ken Springer
Watoga Trail Foundation

Sitting under a tree can make you live longer
– Unless, of course, lighting strikes the tree or it topples over on you.

Outdoor writers, poets and naturalists like John Muir have long advocated spending more time in nature because it is good for your body and your soul. Now, there is hard science to back up this assertion. It would not be an unsupported claim to say that the mere presence of greenery can play a vital role in preventing diabetes, hypertension and obesity, and may even increase longevity.

Admittedly, saying that being around trees can improve your health and even your social interactions sounds a little “New Agey,” but we need to take a look at some long-term research* on the subject. 

Before we get into the “whys and wherefores” of this assertion, I am going to ask that you allow me a paragraph or two to go over the basics of how modern scientific research is conducted.

In brief, the “scientific method” is a series of steps that include making an observation, forming a question, forming a hypothesis, conducting lots of experiments, analyzing the data and drawing a conclusion. Once the hypothesis is well tested, evidential and replicable, then we have a theory.

It is the role of scientists to be skeptical and prove their theories wrong. And, from time-to-time, we read or hear that a long-standing theory has been proven wrong. Probably the most famous debunked theory was the centuries-long belief that the great void of the Universe was filled with something called aether and that this substance facilitated the passage of light and gravity. We now know that aether does not fill the vacuum of space, hence that theory was shown to be wrong. 

This constant challenging and skepticism of theories ensures that we can have the highest possible confidence in them. You do want to know that the medicine you are taking for a serious heart condition is effective and safe, just as you want to know that the plane you are a passenger on will take off and land safely – both are products of the scientific method.

To date, the theory about the effects of greenery on humans has not been disproven, and may never be. So let’s look at what researchers tell us about why we need to see and be around trees, grass and other vegetation to have a healthier life and greater longevity.

Humans, in our current form, have been around some 200,000 years, and our ancestors even longer. In all of that time, except for the last tiny slice, we were always in the presence of greenery – you could say we evolved in a natural habitat surrounded by trees and plants. Then, in the last few hundred years, people began living in crowded, noisy and, sometimes, crime-ridden urban conditions. Like many zoo animals in past years who were deprived of their natural habitat, we also fail to thrive in conditions at odds with the habitat we evolved in.

Today, there are sections of some of the largest cities in the world that are nearly devoid of grass and trees. People living in such places go long periods of time without ever seeing outdoor greenery. And, according to a 30-year research project conducted at the University of Illinois Urbana- Champaign, they are paying the price with adverse health effects.

So, what is it about just having access to greenery on a regular basis that makes our lives so much better? It turns out that just being in green spaces, be they wilderness forests or city parks, has a direct effect on the number of natural killer cells in our bloodstream. These killer cells, also known as lymphocytes, attach themselves to tumors and virus-infected cells, killing them.

When researchers take blood samples from test subjects before and after spending three days in the outdoors, they find a 50 percent increase in the number of natural killer cells following the outdoor experience. And even when blood is tested 30 days later, there is still 25 percent more killer cells than the subject’s baseline number. This does not happen when the three days are spent in an urban habitat without green space.

As an aside to the controlled experiments revealing the positive effects of greenery on the human immune system in cities and the outdoors, the same results were experienced in a laboratory setting with artificial conditions.

When subjects were placed before a computer screen and shown pictures of natural scenes, plus spritzing the air with essential aromatic compounds given off by green plants called phytoncides**, the results of the blood test was the same – more killer cells.

Now, before any of you science-types out there protest that: “Wait just a minute here, what about all of the possible variables like socio-economic factors and the general health and ages, etc. of the test subjects?” 

And to be sure, that is a good question, and we should all be skeptical of outrageous claims. As the famous astronomer Carl Sagan said, “Extraordinary claims require extraordinary evidence.”

But indeed, the researcher Ming Kuo***, of the University of Illinois Urbana – Champaign, says that in one of the experiments, test subjects were assigned to random urban buildings in Chicago. Some had close access to trees and shrubs, others did not. 

The results were that those people in buildings with no access to greenery reported feeling more fatigue and stress. Additionally, there was a breakdown in social interaction among the people living in those buildings.

Of the nearly eight billion people in the world, over half of them live in congested neighborhoods with little or no green space readily accessible to them. The number living in such conditions is expected to rise to two-thirds of the world’s population by 2050. City planners must take note of this type of research if we are to prevent intolerable living conditions and a concomitant rise in crime and disease.

The Watoga Trail Report always urges you to get out and take a hike because it is good for you. Now there is evidence that the positive effects of being in nature are much greater than might be imagined.

Of course, here in West Virginia finding green space is no problem – we are literally surrounded by it. And that is just another great reason for visiting the greenest location of all – Pocahontas County.

Happy and healthy hiking,
Ken Springer

*NPR’s Hidden Brain program Our Better Nature, August 12, 2019
** Phytoncides: a substance emitted by plants to protect them from harmful insects and germs.
*** Ming Kuo, Ph.D. Landscape and Human Health Laboratory. The University of Illinois Urbana – Champaign

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