From The Vancouver Straight: http://www.straight.com/news/523551/david-suzuki-getting-dirty-good-your-immune-system
by David Suzuki
on Nov 5, 2013
For much of human history we lived close to the natural world. As civilization evolved we became increasingly urbanized, and most of us now live in cities. As we’ve moved away from nature, we’ve seen a decline in other forms of life. Biodiversity is disappearing. The current rate of loss is perhaps as high as 10,000 times the natural rate. The International Union for Conservation of Nature’s 2008 Red List of Threatened Species shows 16,928 plant and animal species are threatened with extinction. This includes a quarter of all mammal species, a third of amphibian species and an eighth of bird species. And that’s only among those we know about; scientists say we may have identified just 10 to 15 percent of existing species.
It can be a challenge to communicate why this loss is important. We know species diversity is critical to the healthy functioning of ecosystems that provide services on which humans depend. But could we live with fewer? Some would argue we could do without mosquitoes and other annoying critters. We could keep the ones we want and those that are useful to us. Do we need biodiversity to keep humans healthy?
According to an article in Conservation magazine, there is a link between biodiversity and human health. Ilkka Hanski and his colleagues at the University of Helsinki compared allergies of adolescents living in houses surrounded by biodiverse natural areas to those living in landscapes of lawns and concrete. They found people surrounded by a greater diversity of life were themselves covered with a wider range of different kinds of microbes than those in less diverse surroundings. They were also less likely to exhibit allergies.
What’s going on? Discussion of the relationship between biodiversity and human health is not new. Many have theorized that our disconnection from nature is leading to a myriad of ailments. Richard Louv, author of Last Child in the Woods, says people who spend too little time outdoors experience a range of behavioural problems, which he calls “nature deficit disorder”. It fits with theories of modern ecology, which show systems lacking in biodiversity are less resilient, whether they’re forests or microbial communities in our stomachs or on our skin. Less resilient systems are more subject to invasion by pathogens or invasive species.
Hanski studied a region in Finland where few people move far. He randomly selected 118 adolescents in an equal number of homes. Some were in the city and others in woods or on farms. The team collected skin swabs from subjects and then measured the biodiversity of plants around each house. Their data revealed a clear pattern: higher native-plant diversity appeared to be associated with altered microbial composition on the participants’ skin, which led in turn to lower risk of allergies.