Though it always seems a bit odd to those of us who value it for its own intrinsic sake, the environmental science community has more than once in the last few years attempted to figure out just what nature is worth. Trees always loom large in these assessments. They provide more “services” than you can shake a twig at. And now, it seems we can add one more to the list: Trees help prevent asthma.
Researchers at Columbia University studying asthma in New York City have found that rates of asthma among children aged four and five fall by 25% for every additional 343 trees there are per square kilometer. The more trees we can surround ourselves with, it seems, the fewer of our children will suffer from this debilitating disease.
This is a very important finding because asthma rates have been skyrocketing in recent decades. When Jeffrey and I wrote Naturally Clean a couple of years ago, we found that:
According to a 2004 report from Harvard Medical School, between 1980 and 1994, the incidence of asthma among pre-school-aged children rose by 160 percent, more than twice the rate at which it rose in the overall population. Today, the disease is the leading chronic illness of childhood. Some 9 million children have asthma, or nearly 1 in 13, resulting in 14 million missed school days each year and $3.2 billion in treatment expenses. Our kids aren’t the only ones facing this challenge. The Centers for Disease Control estimates that 7.5 percent of all adults have asthma, too. That’s some 16 million people sick and $9.5 billion in extra health care costs.
Now it appears that trees may be able to help us reverse these troubling trends. The Columbia scientists found a clear association between the number of trees and the number of asthma cases in a given area even after factors like pollution, local affluence, and population density had been accounted for. What’s not clear is what’s at work here. The trees may be aiding air quality or their presence may be encouraging kids to play outside where they’re encountering increased levels of microbes that force their nascent immune systems to toughen up. (See the Hygiene Hypothesis.) Or the trees could simply be more common in neighborhoods whose better upkeep makes them healthier to live in some other way or ways we’ve yet to identify.
More study will have to be done. But it’s certainly clear that there’s some kind of connection between trees and health, between a chronic disease like asthma and the state of our local environment. It’s all the same thing in the end. The health of ourselves is directly linked to the health of our world. Still, if we needed another reason to grow more trees and save the ones we already have, this would be it. Because when we plant trees, we reap a harvest of health for our kids. Speaking as a parent, that’s the only reason I need right there.