Over the past 50 years, the incidence of allergies and immune diseases has gone up while the variety of living things (biodiversity) in our lives has gone down. A new study not only connects these trends, but provides evidence that biodiversity loss may be responsible for increasing health woes.
The study, published in the Proceedings of the National Academy of Sciences, and described in Conservation magazine, builds on past research that links contact with more types of microbes with lower incidence of allergies. In the 1980s, children on farms were found to have less allergy trouble than children in cities; scientists theorized that this may be connected to the greater range of bacteria found in farm environments.
In another study, households with dogs had more kinds of bacteria, but a lower incidence of allergies. This new study finds that people living in houses surrounded by more biodiversity host more types of microbes on themselves, but are less likely to have allergies.
Along with allergies, the prevalence of asthma, Crohn’s disease and other immune-system disorders has soared in recent decades. Together, the studies point to a shared conclusion—exposure to fewer types of organisms makes allergies and other immune disorders more likely, probably because experience with a range of organisms helps our immune systems develop properly.
Immune systems are our bodies’ first line of defense. They identify which organisms are safe, and which pose danger, then attack those with harmful potential. The more species that our immune systems learn to recognize, the more effectively they do the job. When immune systems don’t identify things correctly, they can make mistakes, producing overreaction to pollens, which causes allergies; or attacks on our own cells, resulting in diseases such as multiple sclerosis. Experience with a greater range of organisms may help immune systems develop better ‘radar,’ and more accurately distinguish friend from foe.
Why have our immune systems encountered fewer organisms in recent decades? First, more people live in cities today, and have little contact with natural environments. In addition, biodiversity is declining worldwide in all environments. Natural environments and their species are being lost: polluted, degraded and replaced by buildings and concrete.
American society also seems obsessed with using scads of products to kill bacteria, both good and bad, on ourselves and in our homes; and with applying pesticides heavily to outdoor environments. But evidence indicates that pesticides kill good organisms as well as undesirable ones, and that regular use of antibacterial products may lead to resistant bacteria.
What can you do? One easy action is not to overuse antibacterials. If flu is sweeping your household, antibacterial products may help contain its spread. But regular use of antibacterials in a healthy household probably isn’t necessary.
Further research may help determine effective steps to both increase species diversity and decrease allergy incidence. But until then, consider promoting biodiversity in your yard; research suggests our bodies need much more than grass and pavement. In addition, support efforts to protect and restore natural environments and their biodiversity