US National Library of Medicine National Institutes of Health EMBO Reports, October 7, 2011

The 'Natural immunity' report is fascinating and speaks volumes to the need for us to surround our children with living organisms, not industrial carpets.  The hypothesis, well-founded, is linked to the evolutionary path that humans have taken in concert with the myriad number of life forms that surround us and comprise our bodies. Remember that the human being is comprised of only 10 percent human cells.  

Abstract:  The global decline in biodiversity and the rise of inflammatory diseases might be linked. If the former is causing the latter, it presents a serious challenge for public health.

Excerpt:  We are witnessing two global and deeply worrying trends that, at first glance, seem unrelated. The first trend is the ongoing decline in biodiversity, which is caused by human actions. It could well become the sixth mass extinction of animal and plant species on Earth, comparable in magnitude with the fifth mass extinction at the end of the Cretaceous, 65 million years ago. The second trend is a rapid increase in chronic diseases that are associated with inflammation, especially in developed countries. Inflammation is a key attribute in asthma and allergic diseases, autoimmune diseases and many cancers; even depression has been associated with the presence of inflammatory markers. In this article, we argue that these two phenomena are more closely related than commonly thought: declining biodiversity might actually increase the risk to humanity from chronic diseases and thereby cause a major public health problem.

Overall, one-third of the 56,000 animal and plant species that are sufficiently well known to allow the evaluation of their status are threatened

The processes that link human health and environmental changes are multifaceted, complex and difficult to examine experimentally, but it is clear that microorganisms have a key role

…humans have evolved over millennia to coexist with microorganisms that do not elicit immune responses, but rather induce immunoregulatory circuits

Within the next 30 years, two-thirds of the population in developing countries and almost 85% of the population in developed countries will live in urban areas with little green space

…if biodiversity loss continues unabated, the prospects for public health might indeed be bleak

Chronic inflammatory disorders can be added to the long list of reasons of why we should care for the diversity of animal, plant and microbial life on Earth. We need to consider measures that not only preserve the natural environment but also reconnect us with nature. We need to preserve our connection to the soil and green spaces, we need to expose our children to natural environments, and we need to change food production and transportation, to mention just a few measures. Above all, however, we need to urgently stop the ongoing species extinction—as humans cause it, they also have the power to stop it. Even if molecular biology and biomedical research might eventually develop immune-stimulating treatments to address the burden of chronic inflammatory disease, these will be only paltry substitutes of nature.